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- MATERIALS AND METHODS
- AUTHOR CONTRIBUTIONS
- Supporting Information
Psoriatic arthritis (PsA) is a heterogeneous disease, requiring different outcomes and corresponding instruments to evaluate patients' health status, disease activity, and treatment efficacy (1).
Outcome measures in PsA are not standardized and most of the assessment methodologies have been adapted from clinical trials in rheumatoid arthritis (RA), with few disease-specific instruments for PsA currently available (2). Recently, the Outcome Measures in Rheumatology (OMERACT) proposed a core set of 6 domains of health to be included in randomized clinical trials (RCTs) and observational studies regarding PsA: joints, skin, pain, patient global assessment, physical function, and health-related quality of life (3). This consensus was published in May 2007, but the reporting of this core set in trials and in observational studies is unknown. Other clinical domains considered important for OMERACT and the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) are enthesitis, dactylitis, spine, fatigue, nail disease, and physician global assessment (1, 3). However, instruments to assess these domains have not been agreed on and the frequency of their assessment is unknown.
In the last decade, outcome measures based on patients' opinions, i.e., patient-reported outcomes (PROs), have become critical outcomes in both clinical trials and long-term observational studies in rheumatic diseases (4–6). PROs, defined as any measure of a patient's health status that is elicited directly from the patient and assesses how the patient feels or functions with respect to his or her health condition, reflect the patient burden of disease and feeling of wellness more accurately (7). Furthermore, PROs should be assessed because a discrepancy has been found between patients' and physicians' opinions in several diseases (8–10). Instruments for measuring PROs are easy to administer and some, like the Health Assessment Questionnaire (HAQ), have been proven to be reliable, valid, and sensitive to change (11). There are several ways to explore PROs: some are qualitative (12), whereas others are quantitative such as by assessing the frequency of different outcome measures (4, 5).
The objective of the present work was to assess, through a literature review, which are the most frequently assessed domains and clinical outcomes in recent clinical trials addressing PsA. The specific research questions were: 1) is the OMERACT core set being reported? and 2) are other PROs being assessed and what are the instruments used?
Significance & Innovations
This work evidenced great heterogeneity in the assessment of psoriatic arthritis (PsA) in recent articles relating to PsA; 84 different outcomes were used.
The most frequently assessed outcomes were those proposed in the Outcome Measures in Rheumatology core set; however, there was no consensus regarding the number of joints to assess and instruments for dactylitis and enthesitis.
Patient-reported outcomes were assessed in more than 75% of publications; however, instruments used were heterogeneous and some domains, e.g., fatigue, emotional, and esthetic aspects, were rarely reported.
This study will serve as a reference for the assessment of PsA.
- Top of page
- MATERIALS AND METHODS
- AUTHOR CONTRIBUTIONS
- Supporting Information
The present study evidenced great heterogeneity in the assessment of PsA in recently published clinical trials: 84 different instruments were used. Patients with PsA were mainly assessed using the 6 domains decided on by OMERACT (reported in 37.9–55.2% of articles). However, the core set was rarely completely reported since only 10.3% of the studies reported all 6 core domains. Physician-reported outcomes were heterogeneous and in particular there appeared to be no consensus regarding the number of joints to assess or instruments for dactylitis and enthesitis. PROs were assessed in more than 75% of the publications; however, the instruments used were heterogeneous and some domains, i.e., fatigue, emotional, and esthetic aspects, are rarely reported.
This study has strengths and weaknesses. It may not be exhaustive since the one database assessed was PubMed/Medline; however, this is the most important database of biomedical research articles covering more than 5,000 journals published in the US and more than 80 other countries. Only studies published in English were included; our objective was not to perform an exhaustive review but rather to raise awareness on issues around outcomes in PsA. Another potential weakness was the limitation of the analyses to articles published in the last 4 years; however, the reason for limiting the review to the last 4 years was to include articles published after the dissemination of the consensus on the core set of domains to be assessed in PsA by GRAPPA and OMERACT in 2007 (3). Including recent articles can be responsible for some differences in the number of articles found with the same PubMed search criteria, since there is a time lag between a manuscript's publication and its classification in PubMed. However, recent articles give an up-to-date view on outcomes used in PsA trials.
The classification of the instruments into domains of health was not always easy due to the diversity of scores and questionnaires; however, the data extraction was performed separately by 2 investigators and consensus was high (96.8%). In case of unusual instruments, the authors searched for the primary publication to allow classification into domains of health.
Recent publications indicate that obtaining consensus on outcome measures improves the quality of research (104). The heterogeneity of instruments for assessing disease activity evidenced in this work leads to difficulties in comparing studies, and may lead to the use of nonvalidated instruments. This heterogeneity was present in the assessment of both “objective” measures and of PROs.
For physician-reported outcomes, heterogeneity was mainly noticed for some domains, i.e., joints, enthesitis (both evaluated by 12 instruments), and dactylitis (7 instruments). Other domains had good consensus in terms of instruments, e.g., global assessment evaluated by one instrument, a visual analog scale.
The present work showed that the OMERACT core set is incompletely reported in recent studies. This result may represent the consequence of low dissemination of the OMERACT core set. A possible reason for this observation could be that there is necessarily a lag from the publication of recommendations until they can impact reported outcomes. This is particularly true for trials, as the design and execution take years and the reported outcomes cannot be changed after the trial has started. However, it should be noted that no differences were observed for trials published in 2006–2008 and those published in 2008–2010.
There may also be applicability issues due to a lack of consensus regarding instruments to assess each domain. Further work is ongoing to better define instruments within the GRAPPA and OMERACT groups.
In regard to PROs, heterogeneity has also been found in other rheumatic diseases such as RA, where more than 60 different PRO instruments were described (5). In fact, there is an extensive variety of PROs: the ProQolid (15), for example, includes 689 instruments, and the On-Line Guide to Quality of Life Assessment (105) includes thousands of instruments. Even with the large number of PROs available, some patient-reported domains, such as body image, are not being reported in recent publications. There are few studies in PsA aiming to know which domains are considered the most important in patients' opinions (12, 106). Fatigue is a patient-reported domain described in only 15.5% of PsA articles. However, this domain is considered an important issue in other rheumatic diseases; several qualitative studies (107, 108) have pointed out the importance of fatigue for patients with RA. In RA, fatigue is considered intrusive and overwhelming and has consequences on all aspects of quality of life (107, 108). In PsA, however, there is a lack of data regarding the importance of fatigue for patients.
In conclusion, although PsA patients are mainly assessed, in recent published studies, through the OMERACT core set domains, better consensus on instruments to assess each domain is needed. Furthermore, work is necessary to obtain a better insight into which domains of health are relevant in patients' opinions and which scores and/or questionnaires should be used for their assessment. Qualitative studies based on focus groups or individual interviews with PsA patients can be an alternative for enhancing our knowledge in this field, allowing a better assessment of the disease.