The Asthma Control Questionnaire (ACQ) measures the adequacy of asthma treatment as identified by international guidelines. It consists of seven items (5 x symptoms, rescue bronchodilator use and FEV1% of predicted normal). A validation study suggested that in clinical studies measurement of FEV1 and bronchodilator use may not be needed but this has never formally been tested in a clinical trial. The aims of this analysis were (1) to examine the measurement properties of three shortened versions of the ACQ (symptoms alone, symptoms plus FEV1 and symptoms plus short-acting beta2-agonist) and (2) to determine whether using the shortened versions would alter the results of a clinical trial. In the randomised trial, 552 adults completed the ACQ at baseline and after 13 and 26 weeks of treatment. The analysis showed that the measurement properties of all four versions of the ACQ are very similar. Agreement between the original ACQ and the reduced versions was high (intraclass correlation coefficients: 0.94-0.99). Mean differences between the ACQ and the shortened versions were less than 0.04 (on the 7-point scale). Clinical trial results using the four versions were almost identical with the mean treatment difference ranging from -0.09 (P=0.17), to -0.13 (P=0.07). For interpretability, the minimal important difference for all four versions was close to 0.5. In conclusion, these three shortened versions of the ACQ can be used in large clinical trials without loss of validity or change in interpretation.

Background: Patient-reported outcomes (PRO) questionnaires are being increasingly used in COPD clinical studies. The challenge facing investigators is to determine what change is significant, ie what is the minimal clinically important difference (MCID). This study aimed to identify the MCID for the clinical COPD questionnaire (CCQ) in terms of patient referencing, criterion referencing, and by the standard error of measurement (SEM).

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BackgroundThe aim of this study was to evaluate the association between health-related quality of life (HRQL) and disease severity using lung function measures.MethodsA survey was performed in subjects with COPD in Sweden. 168 subjects (70 women, mean age 64.3 years) completed the generic HRQL questionnaire, the Short Form 36 (SF-36), the disease-specific HRQL questionnaire; the St George's Respiratory Questionnaire (SGRQ), and the utility measure, the EQ-5D. The subjects were divided into four severity groups according to FEV1 per cent of predicted normal using two clinical guidelines: GOLD and BTS. Age, gender, smoking status and socio-economic group were regarded as confounders.ResultsThe COPD severity grades affected the SGRQ Total scores, varying from 25 to 53 (GOLD p = 0.0005) and from 25 to 45 (BTS p = 0.0023). The scores for SF-36 Physical were significantly associated with COPD severity (GOLD p = 0.0059, BTS p = 0.032). No significant association were noticed for the SF-36, Mental Component Summary scores and COPD severity. Scores for EQ-5D VAS varied from 73 to 37 (GOLD I-IV p = 0.0001) and from 73 to 50 (BTS 0-III p = 0.0007). The SGRQ Total score was significant between age groups (p = 0.0047). No significant differences in HRQL with regard to gender, smoking status or socio-economic group were noticed.ConclusionThe results show that HRQL in COPD deteriorates with disease severity and with age. These data show a relationship between HRQL and disease severity obtained by lung function.