Review article: endpoints used in functional dyspepsia drug therapy trials


  • This uncommissioned review article was subject to full peer-review.

Dr J. Tack, Department of Pathophysiology, Division of Gastroenterology, University Hospital Gasthuisberg, Herestraat 49, Leuven B-3000, Belgium.


Aliment Pharmacol Ther 2011; 33: 634–649


Background  The measurement of patient-reported outcomes (PRO) in treatment trials for functional gastrointestinal disorders is a matter of controversy.

Aim  To focus on instruments and endpoints that have been used to evaluate the efficacy of therapeutic agents in functional dyspepsia (FD) trials, also considering the newly defined Rome III FD criteria.

Methods  A Medline search was conducted to identify relevant studies pertaining to FD treatment, with particular emphasis on the studies to date which have used validated outcome measures.

Results  Currently available outcome measures are heterogeneous across studies. They include global binary endpoints, analogue or categorical scoring scales, uni- or multi-dimensional disease specific questionnaires, global outcome evaluations and quality of life questionnaires. Across the available outcome measures, substantial heterogeneity is found, not only in the type of endpoint measure, but also in the number and types of symptoms that are considered to be part of the FD symptom complex. Especially based on content validity, none of the existing questionnaires or endpoints can be considered sufficiently validated to be recommended unequivocally as the primary outcome measure for FD trials according to the Rome III criteria. On the other hand, existing well-validated multi-dimensional questionnaires that include many non-FD symptoms can be narrowed down to evaluate only the cardinal symptoms according to Rome III.

Conclusions  There is an urgent need to develop Rome III-based patient-reported outcomes for functional dyspepsia. Well-validated multi-dimensional questionnaires may serve as a guidance for this purpose, and could also be considered for use in ongoing clinical trials.


Functional dyspepsia (FD) is one of the most prevalent functional gastrointestinal disorders (FGIDs). Over the last 20 years, the definition of FD has undergone major changes from the 1988 working party1 to the consecutive Rome consensus documents,2–4 in line with changing understanding of the pathophysiological basis of this disorder. Based on Rome III criteria,4 FD is defined as the presence of symptoms thought to originate in the gastroduodenal region (early satiation, postprandial fullness, epigastric pain or burning), in the absence of any organic, systemic or metabolic disease that is likely to explain the symptoms. FD is further subdivided into two diagnostic categories of meal induced dyspeptic symptoms [postprandial distress syndrome (PDS), characterised by postprandial fullness and early satiation] and epigastric pain syndrome [(EPS), characterised by epigastric pain and burning]. Whereas the previous Rome II definition3 for FD excluded patients with predominant heartburn and was unclear on nonpredominant heartburn, the Rome III definition states that heartburn is not a gastroduodenal symptom, although it often occurs simultaneously with FD symptoms.4 Similarly, although there is frequent overlap with the irritable bowel syndrome, the symptom pattern of both entities is distinct.

Functional dyspepsia is one of the most important categories of the FGID, in view of its prevalence and impact on the general population.5–8 At present, there is no treatment with established efficacy for FD.1 The Food and Drug Administration (FDA) guidance released in February 2006 provides recommendations for the use of validated instruments to assess treatment outcomes, and describes the proper development and psychometric validation of patient-reported outcomes (PRO) before endorsing a clinical product.9 The Rome III committee10 has also provided guidelines for clinical trial design in FGIDs, with a similar emphasis on individual patient assessment and the use of validated outcome measures. The aim of this study is to evaluate the currently available endpoints for FD drug development, in line with the Rome III definitions, the published FDA guidelines and Rome III clinical trials recommendations.4, 9, 10

Materials and methods

Identification of relevant studies

To identify relevant studies, both computerised (Medline) and manual searches were performed, using the cited references of the retrieved articles. MeSH and free-text terms for FD therapies were combined with the terms dyspepsia, clinical trials, symptom assessment, questionnaires, patient reported measures and randomised for searches conducted for the time period between January 1979 and December 2008. FD therapeutic trials were retrieved and studied, with emphasis on the method used for evaluating outcome measures. Article reference lists were examined for relevant articles. Analysis of both full articles and abstracts was conducted, with particular emphasis on outcome measures. The literature search was performed independently by two of the authors, and their retrievals were merged.

Inclusion criteria

The following criteria were used to select trials for analysis: (i) randomised double blind controlled trials (RCT), (ii) parallel or single cross-over trial designs, (iii) adult patients with FD, (iv) baseline gastroscopy to exclude structural pathology; (v) comparison of therapy vs. active or placebo control; (vi) clear description of the method of assessing outcome measures for FD symptoms and (vii) articles in English.

Outcome measures

One of the main difficulties encountered with therapeutic trials in FGIDs, and FD in particular where efficacy has not been established for any treatment, is the lack of objectively measurable outcome measures.11–14 In FD, symptom patterns do not correlate well with putative pathophysiological mechanisms such as gastric accommodation, sensitivity to distension and gastric emptying rates.15 In the absence of quantifiable surrogate markers for symptom improvement, evaluation of treatment response has to rely on patient’s reporting of symptom intensities.

Several types of outcome measures have been used in FD clinical trials. These can be broadly classified into global outcomes, generic instruments and disease specific instruments.16 Global outcomes are measured either by a dichotomous binary type response (e.g. yes/no to symptom improvement) or a scoring method which can either be a Likert scale (categorical) or a visual analogue scale (VAS). Likert scales allow easier interpretation for the physician compared with the VAS, with 5-point or 7-point scales providing greater sensitivity than 4-point scales.17 The VAS and 7-point Likert scales exhibit comparable responsiveness, although the ease of administration and interpretation of the 7-point scale recommend its use in clinical trials.18 The Likert scale is often incorporated into global scales, such as the overall treatment effect (OTE),19 generic instruments and disease specific instruments. The OTE uses a graded scale to assess overall symptom improvement or deterioration. The subjective nature of this approach allows the individual to integrate all aspects of his condition into a single treatment outcome, and is particularly suitable to show deterioration. Unlike generic instruments, disease specific instruments focus on a particular medical condition and are likely to be more useful in quantifying changes in quality of life in FD therapeutic trials.20 Disease specific instruments in FD can be unidimensional (evaluating gastrointestinal symptoms) or multidimensional (evaluating both gastrointestinal symptoms and other domains such as emotional or social functioning and impact of symptoms on daily activities).

Validity of outcome measures

In 1999, the Rome II Working Group emphasised individual patient assessment as a primary outcome, allowing for the integration of multiple symptoms into a single global endpoint for FGID studies.21 An alternative method was the use of a disease specific questionnaire to evaluate relevant aspects of the patient’s symptoms and disease related quality of life. The Rome III guidelines and the FDA February 2006 guidance provide further recommendations on the proper development and validation of PRO measures.9, 10 Psychometric validation of a symptom based measure incorporates several components, including evidence that the instrument addresses all the patient’s symptoms that are indicative of the disorder (content validity); is related to other measures of the same or similar concepts such as symptom improvement and symptom free days (construct validity); produces similar results when re-administered to patients whose health status has not changed (reliability); detects clinically meaningful change in health status when a change has occurred (longitudinal construct validity or responsiveness); and is associated with changes in score that can be related to clinical indicators that are meaningful to clinicians (predictive or criterion validity). Responsiveness is an important component of validity22 and forms a major criterion for selecting an optimal measure of outcome for a randomised controlled trial.23 Patient involvement in the development of PRO measurement is emphasised by the FDA guidelines, and this can be aided by structured interview sessions, focus groups and quality research methods. The outcome measure should have an effective measurement range,24 allowing the instrument to detect changes in outcomes during the course of the clinical trial without the limitations of the ceiling or floor effects.


Description of studies

Among the therapeutic trials for FD, 117 studies were initially obtained. After excluding 31 studies which did not satisfy the inclusion criteria, 86 studies were selected for analysis of the outcome measures. The outcome measures that were employed in these studies can be classified broadly under the following categories: (i) binary outcome measures (adequate, satisfactory or sufficient relief), (ii) individual symptom assessment with Likert or VAS scales, (iii) disease specific questionnaires, (iv) global outcome evaluations, and (v) quality of life questionnaires. Table 1 summarises the types of endpoints used in the FD studies that were selected for the analysis.

Table 1.   Summary of included trials and outcome measures employed
Outcome measureScoring systemLimitationsReferences
Binary outcome measureAdequate/satisfactory reliefNot Rome III-based
Does not reflect magnitude of improvement
Does not show deterioration
May depend on baseline severity
25, 40, 42, 43, 53
Individual symptom assessment(i) Likert scoresNot Rome III-based
Inclusion of non-FD symptoms
Equal weight to individual symptoms
40, 43–98
(ii) VAS scoreNot Rome III-based99–103
Global evaluationLikert scale/OTENot Rome III-based
Recall bias for OTE
42, 43, 48, 89, 91, 94–98
70–97, 104–107, 110
Disease specific questionnairesGOSNot Rome III-based
Inclusion of non-FD symptoms
Equal weight to individual symptoms
GSRSNot Rome III-based
Inclusion of non-FD symptoms
Equal weight to individual symptoms
82, 88–90, 94–97, 112, 121
LeedsNot Rome III-based
Inclusion of non-FD symptoms
Complex scoring system
91, 92
DSSINot Rome III-based
Inclusion of non-FD symptoms
Equal weight to individual symptoms
42, 116
Hong Kong Index of DyspepsiaNot Rome III-based
Inclusion of non-FD symptoms
Equal weight to individual symptoms
PADYQNot Rome III-based
Inclusion of non-FD symptoms
Equal weight to individual symptoms
Nepean Dyspepsia Index (NDI)Not Rome III-based
Inclusion of non-FD symptoms
42, 43, 91, 92, 122, 129–133
SODANot Rome III-based
Inclusion of non-FD symptoms
Does not assess frequency of symptoms
97, 135
PAGINot Rome III-based
Inclusion of non-FD symptoms
Equal weight to individual symptoms
GDSSNot Rome III-based
Inclusion of non-FD symptoms
Heterogeneous scoring system
Quality of life assessments Not Rome III-based
Not validated as primary outcome measure
102, 108 (primary outcome measure), 66, 70, 72, 73, 78, 98–100, 103–107 (secondary outcome measures)

Adequate relief or satisfactory relief (binary outcome) as a primary endpoint

Evaluating the relief of FD symptoms using a binary outcome approach (yes/no response) was first employed in a study which was designed to compare reflux episodes in FD patients who responded to omeprazole with nonresponders. 25 Responders were defined as patients who considered themselves to have achieved sufficient relief of symptoms at the end of study period. A significantly higher number of reflux episodes on 24 h oesophageal pH measurement were detected in omeprazole responders. Based on extensive experience from irritable bowel syndrome (IBS) studies,26–37 adequate relief and satisfactory relief have been the most commonly used outcome measures in treatment trials for FGIDs, although the Rome III committee on design of treatment trials indicated that further validation may be desirable, and that alternative outcome measures such as integrative symptom questionnaires are also attractive.10

The endpoint of adequate relief is responsive, reproducible and demonstrates good construct validity,38, 39 and has been used in both IBS26–33 and FD40–42 clinical trials. It allows the patient to integrate all relevant symptoms and normalises the assessment to the patient’s own internal reference system.38, 39 On the other hand, the endpoint does not reflect the magnitude of improvement needed to reach the endpoint (which depends in part on the baseline severity level) and does not detect worsening of symptoms.39 Adequate relief was used as a primary endpoint in a phase 2b RCT of alosetron for FD.40 During the 12 weeks of treatment with alosetron or placebo, patients responded yes or no to the weekly question: ‘In the past 7 days, have you had adequate relief of your upper abdominal pain or discomfort?’ A 1 mg dose of alosetron showed benefit over placebo and 0.5 or 2 mg doses for the 12-week average rate of adequate relief. When stratified by gender, alosetron 1.0 mg showed significant benefit in female participants (P = 0.03) in achieving the primary endpoint of adequate relief. Secondary efficacy endpoints were patients’ daily self-rating of symptom frequency (absence or presence of early satiety, bloating, nausea, belching, pain and postprandial fullness) and severity (on a 5-point Likert scale). When the primary global outcome of adequate relief was compared with the secondary outcome of individual symptoms, patients with adequate relief of upper abdominal pain or discomfort also had significantly greater reductions in severity of pain, nausea and bloating, and percentage of days with pain, early satiety, bloating and nausea compared with patients who did not have adequate relief (all P < 0.001). Thus, the adequate relief endpoint showed good correlation when individual symptoms were analysed, but no further validation in FD has occurred. The adequate relief endpoint was also used in a phase 2 U.S. study with Acotiamide, a muscarinic receptor antagonist with fundus-relaxing properties.41 During the first 4 weeks of treatment, the number of subjects reporting adequate relief for more than 50% of time was significantly higher with acotiamide 300 mg t.d.s. compared with placebo.42 This was associated with significant improvement of symptoms of bloating, postprandial nausea, and stomach pain before meals, and with significant improvement of several domains of the Short Form-36 quality of life scale and of the Short form Nepean Dyspepsia Index.42

The satisfactory relief endpoint has a construct that is similar to adequate relief, although less extensive validation data are available in the literature for the former.39 Using satisfactory relief as an endpoint, the beneficial effects of tegaserod in IBS have been demonstrated.34–37 The binary satisfactory relief endpoint was also used in two phase 3 studies with tegaserod in dysmotility-type FD, and demonstrated significant efficacy in one of these.43 In the trial that achieved a significantly higher proportion of days with satisfactory relief from tegaserod, patients also had significant improvement of overall and individual symptom severity measured on a Likert scale, and a significantly better global assessment of change in dyspepsia symptoms.

Categorical (Likert) scales

Likert scales have been widely used both in assessing individual and global symptom severity as well as symptom frequency in numerous FD trials.44–97 Veldhuyzen et al.93 used a 5-point Likert scale (0 = no problem, 4 = very severe problem) to score the severity of eight gastrointestinal symptoms (epigastric pain, burping, heartburn, bloating, flatulence, sour taste, nausea and halitosis). A validation study was performed in non-ulcer dyspepsia (NUD) and Helicobacter pylori associated gastritis (HPAG). Its reproducibility was demonstrated by comparing symptom scores in the two groups of patients before treatment, and responsiveness was demonstrated in both NUD and HPAG patients, where cumulative scores were significantly reduced after therapy. However, the validity of this scale as a measure of improvement was only assessed by comparing changes in symptom scores with changes in the patients’ overall health status (deteriorated, stayed the same or improved during the trial) rather than against an established questionnaire. In addition, it combined FD symptoms with symptoms suggestive of GERD, nausea and intestinal dysfunction. Finally, the cumulative symptom score attributed equal weight to all symptoms, although some of them may be related. Nevertheless, the results from this study support the applicability of a Likert-scale in measuring the severity of FD symptoms.

Likert scores have been employed in numerous studies to date (Table 1), including the BOND and OPERA studies88 which utilised a 4-point Likert scale to evaluate the efficacy of omeprazole in FD. A 7-point Likert scale was used in two very similar multicentre, multinational, RCTs: the OCAY89 and ORCHID studies,90 which compared the efficacy of H. pylori eradication therapy with that of either omeprazole (OCAY study) or placebo (ORCHID study) in relieving dyspeptic symptoms 12 months after eradication therapy. Using a stringent definition of treatment success [absence of symptoms or the presence of only minimal symptoms (Likert score 1 or 2) during the 7 days preceding the final visit] no significant symptomatic benefit of H. pylori eradication therapy in FD was found.89, 90

In addition, Likert scales have been used for global evaluation. Using a Likert-type scale with five grades (symptom-free, markedly improved, moderately improved, not changed and deteriorated) to measure patients’ global assessment of efficacy, a statistically significant benefit was found in a phase IIb trial for itopride over placebo in the number of patients who reported being symptom-free or with marked improvement.91 However, this effect was not seen when the same global patient assessment of efficacy was evaluated in two phase III trials.92

Another method of assessing global outcome is the ‘overall treatment effect’ (OTE) approach.18 At intervals during or at the completion of treatment, the patient is asked to decide whether symptoms have remained the same, improved or deteriorated compared with pre-treatment phase, by means of a Likert scale. The advantage of this endpoint is that it closely resembles the way physicians evaluate treatment benefit in clinical practice, but the main disadvantage is the inherent recall of pre-treatment symptom severity which may lead to bias. OTE was used as a secondary outcome measure in the OCAY study, and in a number of studies of acid suppression in FD.89, 94–97 Overall treatment evaluation was used most recently in the tegaserod FD studies, where a weekly global assessment of change was rated on a 7-point Likert scale, and this endpoint generated the most consistent improvements with tegaserod over placebo.43 OTE was also used in the U.S. and Japanese Acotiamide trials as a secondary or primary endpoint, respectively.42, 98 In the U.S. study, benefit using the OTE paralleled the adequate relief outcome result, with significance during the first 4 to 6 weeks.42 In the Japanese study, significant benefit was found using the OTE for the 100 mg dose in meal-related FD symptoms, and this was associated with a higher rate of disappearance of postprandial fullness and upper abdominal bloating.98 VAS scores, which may be more difficult to interpret in terms of magnitude of response, have been used in only a few, mainly less recent studies.99–104

Disease specific questionnaires (Unidimensional)

Integrative symptom questionnaires incorporate the frequency and/or severity of one or a group of symptoms pertaining to the FGID in question both at baseline and at the end of therapy. A review of the questionnaires that have been used as outcome measures in FD drug therapy trials is pertinent, as they serve an important tool in addressing the effectiveness of pharmaceutical agents. We highlight several instruments that have been developed for assessing outcome measures in FD. Where appropriate, FD trials that have utilised the respective outcome measures are described.

Global Overall Symptom Scale.  The Global Overall Symptoms (GOS) scale is a validated outcome measure for dyspepsia treatment trials,105 adapted from the previously validated 5-point scale.93 Using a 7-point Likert scale, patients are asked to grade the overall severity of 10 upper gastrointestinal symptoms (epigastric pain; epigastric discomfort; heartburn; acid regurgitation; upper abdominal bloating; excessive belching; nausea; early satiety; postprandial fullness and persistent fullness after a meal) [specific symptom subtypes (SSS)] over a certain retrospective period of time, either 28 days (GOS-28) or 2 days (GOS-2). Validation of the GOS was tested within the CADET-HN study94 and the Confirmatory Acid Suppression Test (CAST) study.106 The GOS showed construct validity, reliability and responsiveness.105 Construct validity was determined using Spearman correlation coefficients, by correlating changes in the GOS to changes in severity of individual and mean symptom scores; Quality of Life in Reflux and Dyspepsia (QoLRAD)107 overall score and dimensions the Gastrointestinal Symptom Rating Scale (GSRS, see below)108 overall score and dimensions, and the Reflux Disease Questionnaire (RDQ)109 overall score and dimensions. Moderate to high Spearman correlation coefficient values (0.41–0.80) were achieved for each of the above mentioned outcome measures, demonstrating good construct validity. Test-retest reliability, assessed by Intraclass Correlation Coefficient (ICC) was 0.62 for GOS-2 and 0.42 for GOS-28. In addition, there was a positive correlation between change in GOS and change in symptom severity. To date, the GOS has been used as a primary outcome measure in the CADET (Canadian Adult Dyspepsia Empiric Treatment) study programmes as well as in the ENTER trial.95–97 In this multicentre placebo-controlled trial carried out across Canada, patients with FD of moderate severity (defined as a GOS score ≥4) were randomised to receive esomeprazole or placebo once daily for 8 weeks. For the primary outcome measure of symptom relief (GOS score ≤2 at 8 weeks), no statistically significant difference was found between both groups. However, the GOS combines FD symptoms with symptoms suggestive of GERD or IBS, and the mean score attributes equal weight to all contributing symptoms, which might be considered to be a drawback.

Gastrointestinal Symptom Rating Score.  The Gastrointestinal Symptom Rating Score (GSRS)108 was developed in the early 1980s as an outcome measure for peptic ulcer disease and IBS. It comprises 15 items incorporating five symptom clusters (gastroesophageal reflux, abdominal pain, indigestion, diarrhoea and constipation) over the prior 2 weeks. Although it was originally designed to be interview based with a 4-point adjectival scale, it was subsequently modified to be self-administered with a 7-point Likert scale. The GSRS has been well validated and shown to be responsive.109–111 A shortcoming of the GSRS is that it is not specific for dyspepsia. In addition, it measures only the severity of GI related symptoms and not their impact on quality of life. The GSRS has been used as a primary outcome measure in a study evaluating the efficacy of rebamipide112 and as a secondary outcome measure in various studies.82, 88, 94–97, 113

Leeds Dyspepsia Questionnaire.  The Leeds Dyspepsia Questionnaire (LDQ)114 is administered by an investigator during an interview, and evaluates the frequency and severity of eight symptoms (epigastric pain, retrosternal pain, regurgitation, nausea, vomiting, belching, early satiety and dysphagia). The scoring system uses the frequency of the first five symptoms to determine the presence of dyspepsia, while all eight symptoms are used to access severity of dyspepsia on a scale of 0 (absent) to 5 (most severe). The severity of dyspepsia is assessed as a summary score (range 0–40). The LDQ was shown to be reliable, valid and responsive to change in both primary and secondary care populations in the U.K. Several potential drawbacks of the LDQ include the administration of the questionnaire by a researcher, inclusion of GERD and nausea symptoms, and a complex scoring system.

The psychometric properties of the LDQ were evaluated in 99 primary care patients and 215 hospital referral patients. Physician diagnosis was the gold standard used to validate the ability of the LDQ to detect dyspepsia. The sensitivity and specificity of the LDQ at the primary care setting were 80% and 79% respectively. In the hospital setting, the LDQ showed a sensitivity of 99% while the specificity was 53%. Based on κ statistics, there was moderate to substantial agreement between the LDQ and physician assessment. Test-retest reliability was evaluated in 107 patients by a research nurse during two clinic visits within 4–7 days, yielding a k statistic of 0.83 and internal consistency by Cronbach’s α of 0.68. A similar high k statistic of 0.90 was achieved when two different researchers administered the LDQ to 42 patients within 30 min. Responsiveness to change was also detected, with the median LDQ score decreasing from 22.5 to 4.5 one month after receiving appropriate therapy. However, this was only assessed in 12 patients with relatively severe symptoms. The LDQ has been used in phase 2 and 3 studies of itopride.91, 92 The short-Form Leeds Dyspepsia Questionnaire (SF-LDQ)115 was developed to be self-completed and a shorter version of the original LDQ. The SF-LDQ assesses the frequency and severity over the preceding 2 months of four symptoms (indigestion, heartburn, regurgitation and nausea). In the validation study involving both primary and secondary care patients, Cronbach’s α coefficient was 0.90, demonstrating a high level of internal consistency. Pearson’s correlation coefficient for test-retest reliability 2 days apart was 0.93. Validity was demonstrated by comparison with general practitioners’ diagnosis. Comparison of the summed total scores for patients in the primary care and secondary care setting yielded statistically significant differences, further confirmed the validity of the SF-LDQ. The SF-LDQ’s responsiveness to change was significant in 37 patients who received treatment of known effectiveness.

Dyspepsia Symptom Severity Index.  The Dyspepsia Symptom Severity Index (DSSI)116 is a 20-item self-administered questionnaire divided into three subscales (reflux-like, ulcer-like and dysmotility-like symptoms), quantifying the severity of dyspepsia symptoms over the past 2 weeks. The items were derived from patient focus group interviews. One global item is included at the conclusion of the questionnaire to access the patient’s overall impression of dyspepsia severity. The severity questions are graded on a 5-point Likert scale ranging from 0 (absent) to 4 (very severe). Subscale internal consistency levels were high (Cronbach α 0.84–0.89) and reproducible (ICC 0.90–0.92). The DSSI correlated well with the patients’ symptom diary and discriminated between patients and age-matched controls. However, despite its validity and reliability, its responsiveness was not assessed. Inclusion of GERD and nausea symptoms is another drawback. The DSSI was used in the Acotiamide U.S. Phase 2 programme as a secondary endpoint.42 Significant improvements in symptoms of bloating, postprandial nausea and stomach pain before meals with the 300 mg dose t.d.s., were associated with significantly higher response rates on the adequate relief and OTE endpoints, and with significant improvement of several domains of the Short Form-36 quality of life scale and of the Short form Nepean Dyspepsia Index during the first weeks of the study.42

Other uni-dimensional dyspepsia symptom questionnaires.  The only dyspepsia questionnaire to be validated in a Chinese population, the Hong Kong Dyspepsia Index117 originally contained 24 gastrointestinal symptoms that were self administered, but only the 12 most discriminating symptoms (epigastric pain, upper abdominal bloating, upper abdominal dull ache, epigastric pain before meals, epigastric pain when anxious, vomiting, nausea, belching, acid regurgitation, heartburn, feeling of acidity in the stomach and loss of appetite) were selected. Symptoms are graded on a 5-point Likert scale, ranging from 1 (no symptoms) to 5 (incapacitating symptoms resulting in an inability to perform daily activities and/or requiring days off work). A cut-off score of ≥16 was shown to have a sensitivity of 0.82 and specificity of 0.83 for identification of dyspeptic symptoms. There was good test-retest reliability and internal consistency, with an intraclass correlation coefficient of 0.89 and Cronbach’s α coefficient of 0.90. Dyspepsia scores correlated negatively with all aspects of the SF-36 quality of life scale with the exception of physical functioning, lending support for its construct validity. It was also able to discriminate between patients who reported a subjective improvement in symptoms and those who reported no change or worsening. Although it assesses disease severity, this questionnaire does not measure frequency of dyspeptic symptoms, excludes some key meal-related symptoms (e.g. early satiety) and includes a number of GERD symptoms. This scoring system has been used in a study evaluating the efficacy of 4 weeks of lansoprazole treatment in patients who fulfilled Rome II criteria for FD with a baseline score ≥16.118

The Porto Alegre Dyspeptic Symptoms Questionnaire (PADYQ)119 is an investigator administered unidimensional 11-item instrument which evaluates five symptoms of NUD as defined by the Rome I consensus. The symptoms of upper abdominal pain, nausea and upper abdominal bloating are accessed for intensity, duration and frequency; while vomiting and early satiety are accessed for frequency. Internal consistency of this questionnaire, as measured by Cronbach’s α was 0.82. It was shown to be reproducible when submitted to the test-retest procedure, both by the same interviewer (ICC 0.86) and by different interviewers (ICC 0.87). Its responsiveness was demonstrated by a statistically significant reduction in the mean score obtained after treatment compared with baseline. In addition, the PADYQ demonstrated content, discriminant and criterion validity. However, the questionnaire focuses on the pain spectrum of FD, and does not address symptoms such as postprandial fullness and epigastric burning.

Disease specific instruments (multidimensional)

Nepean Dyspepsia Index.  The NDI120, 121 was developed primarily as a disease specific quality of life measure. From an initial 42-items to measure the impact of dyspepsia on a patient’s overall quality of life, it was shortened to 25-items centred around four subscales: (i) interference with activities of daily living (13 items); (ii) lack of control over the illness (seven items); (iii) disturbance of eating or drinking (three items) and (iv) sleep disturbance (two items). A separate symptom checklist measures the frequency, severity and bothersomeness of 15 common upper gastrointestinal symptoms over a 2-week period. An expert panel documented high internal consistency for the quality of life part of the NDI (Cronbach α 0.81–0.96) as well as good discriminative and convergent validity. The NDI was used as a secondary outcome measure in phase 2 and 3 itopride studies, in tegaserod phase 2 and 3 studies and in the Acotiamide U.S. phase 2.42, 43, 91, 92, 122 Test retest reliability was evaluated in a multi-centre study in the United States.123 The NDI has been translated and validated in several languages, including Arabic.124 The NDI was further shortened to 10 quality-of-life items in five domains.125 This short form NDI was validated in a large multicentre trial in Europe and the United States. The short form NDI demonstrated adequate internal consistency (Cronbach α 0.71–0.76), correlated with the original long version and was highly responsive. To date, one study87 employed both the short and long versions of the NDI, but only the results of the long version were presented.

Severity of Dyspepsia Assessment.  The Severity of Dyspepsia Assessment (SODA)126 is a multidimensional outcome measure for dyspepsia related health that consists of 17 questions incorporating three dimensions of pain intensity (six items); seven nonpain symptoms (belching, heartburn, bloating, passing gas, sour taste, nausea and bad breath) and satisfaction scales (four items). In this self administered questionnaire, patients are asked to assess the preceding 7 days. Reliability was good (Cronbach’s α were 0.97, 0.90 and 0.92 for pain intensity, nonpain symptoms and satisfaction scales respectively) and mean change scores discriminated between patients who reported improvement compared with those who were unchanged. The psychometric properties of SODA were further evaluated in a large study of arthritis patients receiving NSAID or celecoxib, confirming good internal consistency.127

Responsiveness as evaluated by receiver operating characteristic (ROC) curves was high for pain intensity scale [area under the curve (AUC) = 0.78]; nonpain symptoms (AUC = 0.74) and satisfaction scales (AUC = 0.75). However, reproducibility was low, with ICC values of 0.49, 0.61 and 0.45 for pain intensity, nonpain symptoms and satisfaction scales respectively. Notably, SODA assesses the severity but not the frequency of symptoms, and it includes a broad range of symptoms that are also suggestive for GERD or IBS. The SODA was used as a secondary outcome measure in the ENTER trial.97

Patient assessment of upper gastrointestinal symptom severity index and quality of life (PAGI-SYM and PAGI-QOL) questionnaires.  The PAGI-SYM© questionnaire has been developed and validated for the evaluation of symptom severity and treatment responsiveness in upper gastrointestinal disorders such as FD, gastroparesis and GERD.128 It is composed of 20 items in six subscales: heartburn/regurgitation (seven items), nausea/vomiting (three items), postprandial fullness/early satiety (four items), bloating (two items), upper abdominal pain (two items) and lower abdominal pain (two items). Each item is scored from 0 (none) to 5 (very severe). The items were derived from patient focus groups and expert opinion. The PAGI-SYM questionnaire has good internal consistency, reliability and reproducibility over 2 weeks, and adequate content and construct validity in samples of subjects with upper gastrointestinal disorders.128 Responsiveness has been evaluated in an 8-week study in GERD and FD, using OTE as a comparator.129 The questionnaire has also been translated and validated in many different cultural and linguistic settings. Disadvantages of the PAGI-SYM questionnaire are the equal weighting of different symptoms when making up total or subscales, and the inclusion of a broad range of symptoms that are not specific for FD. However, subscales were proposed for use in specific disorders.129 The PAGI-SYM has been used in a study evaluating the 5-HT1A agonist R137696 in FD, where no efficacy was demonstrated.130

The PAGI-QOL questionnaire consists of 30 items in five subscales: daily activities (10 items), clothing (two items), diet and food (seven items), relationships (three items) and psychological distress (eight items). Patients accord a score to each item from 0 (absent) to 5 (severely impaired). It has been validated for evaluating quality of life in FD, gastro-oesophageal reflux disease and gastroparesis by comparing it with the OTE.131

Glasgow Dyspepsia Severity Score.  The Glasgow Dyspepsia Severity Score (GDSS)132 provides a tool for the global evaluation of dyspepsia during the preceding 6 months, and was shown to be reliable, valid and responsive. It records frequency of symptoms (maximum score,5); effect on daily activities (2); the number of days off work because of dyspepsia (2), frequency of medical consultations (2); home visits by a general practitioner (2); clinical investigations performed (2); use of over the counter medications (2) and prescription medications(3). Scores range from 0 to 20, and are significantly lower in healthy volunteers (mean score 1.16) compared with patients with duodenal ulcer (11.1) or FD (10.5). The coefficient of variation was 2% and 8% for intra- and inter-observer assessment respectively. Following eradication of H. pylori in duodenal ulcer, the score changed from 11.4 to 1.3, compared with an average change of 10.5 to 8.5 in patients with persistent H. pylori infection, confirming responsiveness of the GDSS. A score of 0 or 1 on the GDSS corresponds to complete resolution of dyspepsia. Limitations of the GDSS are administration by an investigator and lack of standardised definition of dyspepsia for the investigator to adhere to.

The GDSS was utilised by McColl et al.133 in a trial evaluating the efficacy of H. pylori eradication therapy in non-ulcer dyspepsia. A Spanish translation of the GDSS and a Likert-scale symptomatic test were evaluated for responsiveness to treatment, validity and reproducibility by means of phone interview.134 Both the GDSS and Likert-scales were valid (higher scores in patients undergoing endoscopy than in healthy controls); had adequate response after subjects completed H. pylori eradication therapy, and showed low intraobserver variation whether the interviews were conducted by phone or by a combination of phone and clinical interview. The GDSS was superior to the Likert-scale in remaining reproducible even when conducted by different observers.

Other disease specific multidimensional instruments.  The Clinical Dyspepsia Questionnaire is a condition specific self-administered measure of dyspepsia and peptic-ulcer related symptoms. It assesses the frequency and severity of symptoms and their impact on QOL.135 Patient scores on this questionnaire reviewed only small to moderate correlations (0.20 to 0.66) with the SF-36 quality of life survey, but further validity tests showed significant correlations with general practitioner perceptions of symptom severity, family history of peptic ulcer disease and whether patients were referred. Test-retest reliability yielded an intraclass coefficient value of 0.69. However, responsiveness was not assessed.

The Gastrointestinal Symptom Score (GIS) is a 10-item questionnaire developed for the study of FD.136 It was developed based on patient focus groups, and validated by comparison with the Nepean Dyspepsia Index. However, the questionnaire includes typical GERD symptoms like heartburn, regurgitation and retrosternal discomfort. The GIS has been used in studies of herbal medicines in FD.137–139

Quality of life measures

Quality of life (QOL) measures can be assessed either by generic instruments or by disease specific measures. The Short Form of General Health Questionnaire (SF-36)140 is a generic instrument that has been widely used in various disorders. To evaluate more specifically QOL in specific disorders, such as in functional gastrointestinal disorders, questionnaires that are available include the Nepean Dyspepsia Index (NDI)120–125 for FD, the PAGI-QOL for upper GI disorders128 and the IBS-QOL141 for IBS. Although these quality of life measures have been strongly recommended as secondary outcome measures, they are not utilised as primary outcome measures as they are regarded by regulatory agencies as being insufficiently responsive to treatment, although this may not necessarily be correct.10

Various trials have measured QOL as primary or secondary outcome measures (see Table 1). In a recent trial of tegaserod for dysmotility-type FD, significant improvement in treatment satisfaction and reduced work and daily activity impairment were reported in the treatment group compared with placebo.142


Evaluating the therapeutic efficacy of drugs in FD remains challenging because of the variable intensity of symptoms in one individual and the high placebo response rates.13, 143–147 The choice of the endpoint for a clinical trial is a key factor in assessing therapeutic efficacy. However, there is a lack of consensus on the best method to measure clinical outcome in FD drug trials.13, 14 In this setting, the most recent mandate emphasises the use of PRO in symptom reporting.9 The dichotomous endpoint of adequate or satisfactory relief has seen increasing use as primary endpoint in recent trials, while alternative outcome measures such as integrative questionnaires are also considered potentially acceptable, but these views seem largely driven by experience with IBS trials.26–37

Achieving the adequate relief endpoint in clinical drug trials was instrumental in obtaining FDA approval initially for ranitidine for the treatment of heartburn,148 for alosetron in IBS,26–28 and subsequently for tegaserod in IBS (using satisfactory relief).34–37 Evidence supporting responsiveness of the adequate or satisfactory relief endpoints was documented mainly in IBS trials, where the binary endpoint correlated with other standard measures of treatment efficacy.26–37, 149–151

On the other hand, limitations of the binary endpoints include the lack of sensitivity and validation, inability to detect worsening of symptoms (unlike the OTE), lack of information on the magnitude of improvement needed to reach adequate relief, the potential for failure to report adequate relief in subsequent weeks once achieved, the influence of baseline severity of symptoms and response outcomes and variable interpretation of the adequate relief construct.39 Based on an observational IBS study in a health maintenance organisation setting, it has been suggested that patients with mild symptoms at baseline are more likely to achieve satisfactory relief compared with those with severe symptoms at baseline.152 Contrary to this suggestion, the greatest improvement in percentage of days that FD patients reported satisfactory relief of symptoms occurred in those who had severe baseline symptoms compared with those who had mild symptoms (P < 0.05).43 Hence, the use of binary relief endpoints in FD deserves additional validation studies. Compared with questionnaires that use specific FD symptoms, the binary or overall treatment evaluation question may be more suitable to capture an overall treatment impact in functional disorders, especially as this approach has the potential to also contain changes in associated more global symptoms (e.g. fatigue).

In addressing the use of an acceptable alternative outcome measure, a questionnaire should undergo appropriate psychometric validation in accordance with the FDA guidance regulations and Rome III guidelines on clinical trials.9, 10 In our opinion, existing questionnaires present some methodological flaws, mainly because of the failure to satisfy the psychometric property of content validity. In the light of the Rome III criteria,4 none of the existing questionnaires are sufficiently validated to be recommended unequivocally as the primary outcome measure for FD trials. Central to the problem of previously validated questionnaires was the inclusion of many symptoms which are not considered cardinal FD symptoms according to current criteria.4 An adequate and valid questionnaire, i.e. one that incorporates all the psychometric validation standards, in particular incorporating the Rome III criteria for FD, would facilitate future therapeutic trials in FD.

The absence of a validated instrument for the evaluation of treatment efficacy in FD according to Rome III criteria and the lack of robust psychometric validation data for the binary outcome measure in FD trials should not impair ongoing or planned drug development in this area. One plausible solution is to build upon the heritage of current instruments to serve as a useful framework in designing a new questionnaire. Existing questionnaires that include many non-FD symptoms can be narrowed down to evaluate only the cardinal symptoms according to Rome III. Such an approach was used in the itopride phase 2 and 3 studies, which used two FD-specific questions (severity of epigastric pain and of postprandial fullness) from the LDQ as co-primary endpoint, whereas the full LDQ score was a secondary endpoint.91, 92 The most valuable questionnaires are probably the ones that used patient focus groups to identify relevant symptoms, such as the DSSI, PAGI-SYM or GIS questionnaires.116, 120, 128, 136 Another possibility is to incorporate the OTE with the binary endpoints of adequate or satisfactory relief, for which there is extensive experience from IBS trials26–37 and emerging experience from FD trials.25, 40–43 The OTE was extensively used in the OCAY, CADET and ENTER trials89, 94–97 and most recently in the tegaserod and acotiamide studies.42, 43 The subjective nature of the global outcome approach or OTE allows the individual to integrate all aspects of his condition into a single treatment outcome. Although the OTE is particularly suitable to show deterioration, it is prone to recall bias as it compares current symptoms to pre-treatment severity. Nevertheless, using both the OTE and binary outcome to evaluate treatment efficacy would provide valuable information both from a global perspective as well as in assessing symptom improvement and/or deterioration.

Similar to other FGIDs, the magnitude of the placebo response is a major concern in the evaluation of efficacy of drugs in FD. The available recent studies do not show a major difference in responder rate when comparing binary endpoints to OTE responses or to responder rates on composite questionnaires like the LDQ or DSSI, provided the cut-off level for response was adequately chosen.42, 43, 92 Indeed, these studies illustrate how the magnitude of the placebo effect depends on the level of improvement used to define a responder. For instance, in the itopride phase 3 trials, an improvement of 1 point on the LDQ had a placebo response of 70–75%; when a 2 point improvement was chosen as response definition, the placebo response was 45–55%, quite similar to the placebo response on a global patient assessment of efficacy.92 Similarly, requiring a 50% weekly response rate over a 75% weekly response rate is associated with a higher placebo rate.42, 43 In addition, the tegaserod phase 3 studies showed a high placebo response rate, and a low therapeutic gain of active drug over placebo, when patients with mild symptoms were considered, while a bigger therapeutic gain over placebo was obtained in those with moderate or severe symptoms.43 Hence, to minimise the placebo effect, inclusion of patients with at least moderate symptom severity, and the choice of a high enough threshold for response definition is recommended.

Some studies in FD have used elimination of symptoms, usually measured on Likert scales, as an endpoint.98, 113, 133 Although it is clear that becoming asymptomatic is clinically relevant, the proportion of patients with functional gastrointestinal disorders in whom this can be achieved by a pharmacological intervention (and by the comparator placebo arm) is likely to be low. Placebo responses are indeed low when this endpoint is considered.98, 113, 133 Elimination of symptoms, therefore, probably sets a very high threshold for response and focusing on this endpoint induces a risk of disregarding clinically relevant degrees of symptom improvement in FD and other FGIDs. International consensus guidelines, as well as FDA guidance, therefore focus on identifying and recognising significant symptom improvement using validated scales,9–13 rather than symptom elimination which can still be considered a useful secondary outcome variable.

No regulatory guideline exists on which magnitude of an active drug response rate over placebo is needed to be considered clinically relevant. This was also not specifically addressed by the Rome III working committee on design of treatment trials in functional disorders.10 However, a group of experts proposed a minimal range of efficacy of 10–15% over placebo to be clinically relevant for functional disorders and for the irritable bowel syndrome in particular.153 It seems reasonable to assume that the same magnitude of margin over placebo could also be considered clinically relevant in FD.

In conclusion, there are emerging data on the use of binary outcome measures in FD clinical trials, although further validation is required. Most existing questionnaires do not sufficiently fulfil psychometric validation criteria, in view of the latest consensus definitions of FD by Rome III criteria. Hence, evaluating and comparing the various options will need to go hand in hand with the analysis of recent, ongoing or future pharmaceutical trials for the treatment of FD, and optimization of potential endpoints that could be derived from existing instruments.


Declaration of personal interests: None. Declaration of funding interests: Pieter Janssen is a research fellow of the FWO Flanders. This work was supported by a Methusalem grant to Jan Tack.