Discriminative properties and validity of a health status questionnaire in obstructive airway disease patients: the airway questionnaire 20

Abstract

Objective: To evaluate the discriminative properties and validity of the Airways Questionnaire 20 (AQ20) in a sample of airway obstructed patients and to compare its properties with those of the St George's Respiratory Questionnaire (SGRQ) and the Short Form 36 (SF-36). Patients and methods: A convenience sample of 47 subjects was recruited from among 61 consecutive patients referred to an outpatient clinic specialized in airway obstructive diseases. All subjects completed the AQ20, SGRQ, and SF-36. Other measures were the baseline dyspnea index (BDI),6-minute walk test (6MWT) distance, spirometry, results of arterial blood gas analysis, and body mass index. RESULTS: The AQ20 showed very good correlation with the SGRQ total score (ρ = 0.84, P < .001) and moderate correlation with all SF-36 domains (physical capacity, ρ = −0.53;physical functioning,ρ = −0.61;bodily pain, ρ = −0.55;general health,ρ = −0.59;vitality,ρ = − 0.55;;social functioning,ρ = −0.57; emotional role functioning,ρ = −0.51; mental health,ρ = −0.61;all P < .001).The BDI and the 6MWT were the best predictors of AQ20 score (r2 = 0.31) in the regression model. An area under the receiver operating characteristic curve of 0.91 (P < .001) indicated a high level of accuracy for the AQ20, using the SGRQ as the gold standard. Conclusion: This study shows that the AQ20 is an accurate health status questionnaire in patients with moderate-to-severe airway obstruction. It could be an alternative to longer, traditional questionnaires such as the SGRQ.