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Background: Illness as perceived by the allergic patient with asthma and/or rhinoconjunctivitis (RC) can be assessed by measurements of their health-related quality of life (HRQL). For this purpose the RC Quality of Life Questionnaire (RQLQ) has gained general acceptance; however, as most allergic patients experience symptoms from multiple organs, disease-specific HRQL measures may be deficient. This study compares a generic and a disease-specific HRQL instrument in grass and/or mite-allergic patients.
Methods: Two hundred and forty-eight patients with RC and 121 patients with both RC and asthma were studied. Questionnaire information was obtained about allergy-related RQLQ and a generic 15-dimensional instrument for measuring HRQL (15D). Doctors provided general and disease-specific information to classify disease severity according to the global initiative for asthma and allergic rhinitis and its impact on asthma guidelines.
Results: Rhinoconjunctivitis patients with persistent moderate-to-severe disease had an impaired quality of life on all items of RQLQ during allergen exposure. The 15D mean score was 0.98 on a day without allergy and 0.83 on a day with allergy (P < 0.001). The correlation between 15D and RQLQ was r = −0.42 on a day with allergy (P < 0.001). Only 15D scores showed statistically significant differences in HRQL between patients with and without asthma.
Conclusion: During allergen exposure patients with RC experience a serious deterioration in HRQL measured with the disease-specific RQLQ instrument and the generic 15D instrument. The 15D instrument seems to generate a more comprehensive view of the impact of allergen exposure on patient’s quality of life than RQLQ.
Allergy to airborne particles results in co-morbid conditions with symptoms from eyes, nose, and lungs. Up to 40% of the patients with rhinitis also have asthma, and up to 80% of the patients with asthma experience nasal symptoms. The two conditions can be regarded as an allergic respiratory syndrome (1–3). Allergic asthma and rhinoconjunctivitis (RC) are common respiratory diseases. In Europe, approximately 25% of the population suffers from respiratory allergy. The prevalence of asthma and RC has increased in industrialized countries over the past decades, and thus, allergies constitute a public health problem (4, 5). The allergic diseases impair physical, psychological, and cognitive functions, and the impact on the patient’s health-related quality of life (HRQL) is frequently underestimated. Interventions against respiratory allergy include symptomatic treatment, allergen avoidance, and allergen-specific immunotherapy.
It is widely acknowledged that the personal burden of illness, as perceived by the allergic asthma and/or RC patient, cannot be fully assessed by traditional clinical symptoms and signs correlating only moderately with patients’ perceptions and functional capabilities on a daily basis (6, 7). Specific instruments, such as the RC Quality of Life Questionnaire (RQLQ), have gained acceptance as methods to obtain a measure of disease perception in adults with RC (8, 9). Generic HRQL instruments have only been examined sporadically in allergy (10–14), and to our knowledge never with the generic 15-dimensional instrument for measuring HRQL (15D) instrument (15).
Specific instruments focus on health outcomes related to a specific disease, medical condition, or patient population. They concentrate on dimensions (or domains) of HRQL that are most relevant to the disease in question. The specific instruments are more responsive to changes in the particular disease-related aspect of the patient’s HRQL compared to generic instruments, which focus on the patient’s general health. Furthermore, it is likely that patients and physicians consider these instruments more relevant compared to generic instruments (16, 17). The main disadvantage of specific instruments is that they cannot be used to compare the quality of life across different diseases and patient types, and therefore cannot be used to compare the relative effectiveness and cost-effectiveness of programs in different disease areas. RQLQ is a validated and reliable instrument, but it does not produce a single quality of life score, but rather a profile of scores across different domains. In addition, scoring is not based on individual preferences for the various possible outcomes. Consequently, it is not clear whether high scores are associated with outcomes that are more or less preferred by the patient.
Generic instruments are broad-based measurements that can assess general HRQL over different disease states and conditions, treatment interventions, and population states. Generic instruments allow comparison of HRQL for different disease states, such as allergic RC, asthma, hypertension, and diabetes. Typically, they include consideration of physical functioning, ability for self-care, physiological status, level of pain or distress, and amount of social integration. Generic instruments can also serve as health profiles. The major disadvantage of generic instruments is the inclusion of items not relevant to the disease, and furthermore, the sensitivity may not be sufficient to differentiate between different levels of quality of life within a particular disease. Examples of generic instruments are the short form (SF) 36, the Nottingham Health Profile, the Sickness Impact Profile, the EQ-5D (18, 19), and the 15D. Only generic instruments based on public preferences, such as the EQ-5D and 15D can serve as a basis for comparison of the cost-effectiveness of programs in different disease areas. The 15D instrument for HRQL contains both a profile and a utility measure.
The present study compares results obtained by using the disease-specific RQLQ and the generic 15D instrument in the same population of adult allergic patients enrolled for subcutaneous injection immunotherapy (SCIT) against grass and/or house dust mites, so the impact of seasonal allergen exposure could be investigated. Previous studies have reported a relationship between disease severity and use of medication and health care services (20–22). The aim of the current study was to address a potential correlation between disease-specific and generic HRQL and disease severity classification of hay fever and asthma.
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The study included 254 grass and/or house dust mite allergic patients, who were referred to specialist centers with an indication to start SCIT between September 2005 and December 2006. One hundred and twenty-nine of the participants were men. One hundred and seventy patients were about to start SCIT with grass pollen alone, 30 were about to start SCIT with house dust mites only, and 54 were about to start vaccination against both grass pollen and house dust mite (Table 1).
Table 1. Categorization of the patients by vaccination modality
| ||Vaccination with grass pollen extract only, (n = 170)||Vaccination with house dust mite extract only, (n = 30)||Vaccination with grass pollen and house dust mite extracts, (n = 54)|| Total (n = 254)|
|Male||92 (54.1)||10 (33.3)||27 (50.0)||129 (51.0)|
|Female||78 (45.9)||20 (66.7)||27 (49.1)||125 (49.0)|
|Mean (SD) age in year [range in year]||33.4 (10.4) [16.1–64.4]||35.3 (9.4) [21.6–59.8]||33.2 (12.5) [16.1–66.3]||33.6 (10.8) [16.1–66.3]|
|Mean (SD) years with doctor diagnosed allergy [range in year]||15.0 (10.0) [1–44]||11.2 (9.6) [1–40]||14.0 (10.3) [1–45]||14.0 [1–45]|
|Mean (SD) years with self-reported allergy [range in year]||18.0 (11.1) [0–47]||14.3 (10.3) [0–41]||17.2 (12.9) [3–54]||17.4 (11.4) [0–54]|
There were no significant gender differences concerning the allergens with which vaccination was going to be initiated. Two hundred and forty-eight (97.3%) of the patients were diagnosed as RC patients, among those 127 (49.8%) were diagnosed as suffering from RC only. Six (2.4%) were diagnosed as bronchial asthma only and 121 (47.5%) of the patients were diagnosed as both RC and bronchial asthma (Table 2). The mean self-reported disease duration was 17.4 years. The doctors reported the mean time since diagnosis as 14.0 years. Hence, the average allergic patient in this study had suffered from allergic symptoms for 3.4 years prior to a doctor’s diagnosis (Table 1).
Table 2. Baseline diagnosis of the rhinoconjunctivitis patients according to ARIA and the asthma patients according to the GINA guidelines by vaccination modality
| ||Vaccination with grass pollen extract only, 170||Vaccination with house dust mite extract only, 30||Vaccination with grass pollen and house dust mite extracts, 54||Total 254|
| No rhinoconjunctivitis diagnosis||1 (0.6)||5 (13.6)||0||6 (2.4)|
| Intermittent mild||2 (1.2)||3 (10.0)||1 (1.9)||6 (2.4)|
| Intermittent moderate to-severe||5 (2.9)||1 (3.3)||3 (5.6)||9 (3.5)|
| Persistent mild||12 (7.1)||0||9 (16.7)||21 (8.3)|
| Persistent moderate-to-severe||150 (88.2)||21 (73.1)||41 (75.9)||212 (83.5)|
| No asthma diagnosis||88 (51.8)||13 (43.3)||27 (49.1)||128 (50.4)|
| Intermittent ||29 (17.1)||6 (20.0)||7 (12.7)||42 (16.5)|
| Mild persistent ||21 (12.4)||1 (3.3)||6 (10.9)||28 (11.0)|
| Moderate persistent ||29 (17.1)||8 (26.7)||11 (20.0)||48 (18.9)|
| Severe persistent ||3 (1.8)||2 (6.7)||4 (7.3)||9 (3.5)|
Regression analyses of RQLQ and 15D, respectively on a typical day with allergy, on gender, age, vaccination modality, and disease severity are presented in Table 3. In the regression analysis, we omitted the six patients who were suffering from asthma only to simplify the interpretation of the coefficient associated with asthma (which then reflects the added health consequences of having asthma in addition to RC).
Table 3. Regression analysis of RQLQ and 15D on gender, age, vaccination modality, hay fever severity, and asthma severity on a typical day with allergy
|Vaccination against house dust mite||0.0551||0.2318||0.812||−0.0325||0.0184||0.079|
|Vaccination against house dust mite and grass||−0.7171||0.1598||0.000||0.0008||0.0120||0.946|
|Hay fever moderate-to-severe||0.4026||0.2056||0.052||−0.0415||0.0128||0.001|
|No of observations||170||240|
Females reported statistically significantly lower HRQL scores compared to men on both instruments. The sign of the coefficients to the covariate age were in accordance on the two instruments. On the 15D instrument, an increasing age was statistically significantly associated with a higher HRQL score on a day with allergy. Both instruments produced statistically significantly different scores for patients classified as ‘no or mild’ RC and those classified as ’moderate-to-severe’. The RQLQ did not differentiate between patients as those with or without asthma and between different severities of asthma. The 15D questionnaire on the other hand showed a statistically significant difference between patients with and without asthma (Table 3).
On the RQLQ instrument, the respondents reported statistically significantly higher quality of life if they were about to start SCIT with both grass pollen and house dust mites as compared to patients that were about to start SCIT with grass pollen only (P = 0.000).
All 15 items on the generic 15D questionnaire comparing a typical day without allergy with a typical day with allergy is presented in Fig. 1. The respondents hardly had any problems on a day without allergy measured with 15D. On a day with allergy, however, the scores were statistically significantly higher on the five digit ordinal scale (P < 0.001) for all 15 items meaning that HRQL on a day with allergy was statistically significantly lower compared to a day with no allergy. The mean utility score on a day with no allergy was 0.98 (SD 0.03) compared to 0.83 (0.08) on a day with allergy. The difference between the scores was 0.15 (0.07) (P < 0.001).
Figure 1. 15D profile of patients (n = 254) screened to SCIT on a day without allergy (−A), and on a day with allergy (+A).
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The ‘overall’ mean score on a day with allergy on the RQLQ instrument was 3.1 (0.9). The domain item ‘activity’ had the highest mean score of 4.4 (1.2) meaning it was the item affecting the respondents most. The item ‘sleep’ had the lowest mean score of 2.1 (1.6) meaning that it was the item least affecting the respondents on the RQLQ instrument (Fig. 2).
Figure 2. RQLQ profile of patients (n = 254) screened to SCIT on a typical day with allergy. The domain item ‘activities’ are illustrated by the bars activity1–3. Respondents made a choice between 29 different activities, which were limited by their nose/eye symptoms. The domain item ‘sleep’ is illustrated by the bars sleep1–3: sleep1, difficulties getting to sleep; sleep2, wake up during night; sleep3, lack of good night’s sleep. The domain item ‘Non-nose/eye symptoms’ is illustrated by the bars 7–13. The domain item ‘Practical problems’ is illustrated by the bars 14–16: 14, inconvenience of having to carry tissues or handkerchief; 15, need to rub nose/eyes; 16, need to blow nose repeatedly. The domain item ‘nasal symptoms’ are illustrated by the bars 17–20. The domain item ‘eye symptoms’ is illustrated by the bars 21–24, and the domain item ‘emotional’ is illustrated by the bars 25–28. (For a detailed description see Appendix A.
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On all domain items on the RQLQ instrument, women reported a lower HRQL. For the five domain items and the overall-score, the difference between gender was statistically significant (P ≤ 0.05). On 12 out of 15 items on the 15D instrument, women had a lower HRQL score as compared to men. On the six items ‘mobility’, ‘breathing’, ‘sleeping’, ‘elimination’, ‘depression’, and ‘vitality’, this HRQL was significantly lower compared to that of males (P ≤ 0.05).
According to the ARIA classification, all RQLQ domain items, (with the exception of the ‘emotional’ item), the patients classified as ‘moderate-to-severe’ RC had statistically significantly lower HRQL, as compared to patients classified as ‘no or mild’ RC (P < 0.05). The utility scores on the 15D instrument measured the same difference between these two severity groups (P = 0.01) on a day with allergy, whereas on a day with no allergy there was no difference (P = 0.99). On 13 out of 15 items on the 15D instrument patients diagnosed with ‘moderate-to-severe’ RC had lower HRQL scores as compared to patients diagnosed with ‘no or mild’ RC. On the items ‘mobility’, ‘breathing’, ‘sleeping’, and ‘vitality’ the scores were statistically significantly lower (P ≤ 0.05), indicating that the 15D instrument was capable of differentiating patients according to disease severity.
On a typical day with allergy there was a negative correlation between the two instruments as shown in Fig 3. The correlation between the 15D score and the RQLQ overall score was r = −0.42 (P < 0.001). The correlation between the seven RQLQ domain items and the 15D items was assessed to see which domains were linked Table 4.
Table 4. Correlation between 15D items and RQLQ domain items on a day with allergy
|15D items||RQLQ domain items|
|Activity (n = 180)||Sleep (n = 244)||Non-nose/eye symptoms (n = 243)||Practical problems (n = 246)||Nose problems (n = 242)||Eye problems (n = 245)||Emotions (n = 245)||RQLQ Overall (n = 168)|
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In recent years, it has become increasingly clear that co-morbid disease conditions are the rule rather than the exception in allergy. Allergic patients exclusively suffering from asthma are rare. Although this is not an epidemiological study, only six out of 254 patients included did not show signs of RC. According to the ‘one airway, one disease’ concept introduced in the ARIA document, allergy is a systemic condition in the immune system and asthma and RC can be considered local manifestations of this underlying immunological condition.
The 15D instrument demonstrated that allergy affects all dimensions of life, signified by a statistically significant movement on all 15 items on a day of allergy. The 15D and the RQLQ instruments both showed a statistically significantly lower HRQL for women. Patients diagnosed with ‘moderate-to-severe’ RC had a statistically significantly lower HRQL than patients with ‘no or mild’ RC. This was found for all items on both instruments, confirming the hypothesis that a more severe RC diagnosis correlates with a lower HRQL. On the 15D instrument higher age was statistically significantly associated with a higher HRQL score. This was not observed on the disease-specific RQLQ instrument. This result suggests that older people are better at coping with their allergy, a factor which is not captured by the RQLQ instrument.
In this study, the patients were interviewed just prior to the start of SCIT treatment. To the extent that respondents have an inclination to justify their choice of SCIT by exaggerating their symptoms on a day with allergy, this may bias the presented results. Another potential source of bias in the study was that the patients were self-selected to the study; hence they are unlikely to be representative of the population of allergy patients. There was no possibility, however, of a baseline analysis, as patients were enrolled only when appearing at the specialist center for the purpose of initiating SCIT treatment.
Patients filled in the questionnaires as they recalled a typical day caused by allergy and a typical day without allergic symptoms. Although this method may have introduced recall bias as compared to studies in and out of the pollen season, results obtained in this study (RQLQ-overall score = 3.1) did not differ substantially compared to previous studies (9, 33, 34).
This study shows that is was possible to measure a difference in the HRQL on the generic preference-based 15D utility instrument among allergic patients, and that the burden of disease was significant for this particular group of patients. The correlation analysis of the two instruments showed that they were statistically significantly correlated; the correlation coefficient was (−0.42). Analysis of correlations between the two instruments dimensions generally showed coefficients of equal or lower magnitude (Table 4). Interestingly, those 15D dimensions which appeared to be most sensitive to HRQL changes amongst the allergy/asthma patients did not correlate strongly with any of the RQLQ dimensions, suggesting that there are elements of HRQL which are not adequately captured by the RQLQ instrument. What is also clear is that the RQLQ dimensions ‘Non-nose/eye symptoms’ and ‘Emotions’ are most markedly associated with general HRQL.
In accordance with the previous studies, we found that the RQLQ scores do not differ statistically significantly across patients both with and without an asthma diagnosis RC Quality of Life Questionnaire is a tool developed for specific evaluation of patients suffering from RC. In the light of the ‘one airway, one disease’ concept, this can be regarded as a major shortcoming. A comprehensive assessment of allergic RC patients needs not only to take symptoms from the nose and eyes into consideration, but also symptoms from the lungs. The understanding of allergy being a systemic, immunological condition underlying asthma and RC has only surfaced recently; however, the present study seems to suggest that it has implications for HRQL assessment. For many years the common use of the RQLQ may have underestimated the real burden of disease in patients with allergic RC, as symptoms from the lungs were ignored by the RQLQ, although these are present in a large proportion of the RC patients. The present study indicates that the generic instrument 15D is capable of providing a more balanced view of the HRQL impairment in patients suffering from inhalation allergy.
The 15D instrument and the RQLQ instrument were capable of differentiating RC patients across different disease severities. The 15D instrument was, in addition, capable of differentiating asthma patients from nonasthma patients. The 15D appears to be able to capture dimensions of HRQL, which are not incorporated in the RQLQ. One of the strengths of the 15D instrument is that the total score is a weighted average across several dimensions, with the assignment of relative weightages based on the public preferences. In contrast, the RQLQ score is based on an unweighted average, which implicitly assumes equal weightage. Hence, a comparison of RQLQ scores across health states which involve problems on more than one dimension may be invalid.
An additional advantage of including generic instruments (such as the 15D) in evaluations of interventions targeted at allergy patients is that such measures are preference-based, allowing for calculation of quality adjusted life-years. The quality adjusted life-year is a generic outcome measure. Such evaluations represent a useful tool for decision makers and may be a valuable input for optimizing the resource allocation across different patient groups.
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Appendix S1. Health economic analyses of treatment strategies for allergic respiratory tract illnesses (SABAL).
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Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.