Background and objective: There is increasing international interest in using patient-based outcome measures to evaluate interventions. We compared responses to postal administration of Mini Asthma Quality of Life Questionnaire (MiniAQLQ) and Asthma Control Questionnaire (ACQ) with the gold standard of supervised self-completion.
Study design and setting: Validation study involving 96 adults, recruited from U.K. general practice, sent the postal questionnaires with an instruction sheet 1 week before supervised self-completion. Responses for those whose quality of life (n=56) or asthma control (n=61) had 'not changed' between postal and supervised completions were compared using paired-sample t-tests, Pearson's correlation coefficient (r), and intraclass correlation coefficient (ICC).
Results: For the MiniAQLQ, overall mean scores were similar in both groups: Postal=5.14 (SD=1.42) vs. Supervised=5.17 (SD=1.39), with mean difference of -0.03 (95% CI=-0.14, 0.08; P=.59), with a high degree of correlation (r=.96, P<.001) and concordance (ICC=0.96; 95% CI=0.93, 0.98; P<.001). For the ACQ, overall mean scores (with SD) were also similar in both groups: Postal=1.24 (SD=1.09) vs. Supervised=1.26 (SD=1.10), with mean difference of -0.02 (95% CI=-0.12, 0.08; P=.74), with good correlation (r=.94, P<.01) and concordance (ICC=0.94; 95% CI=0.90, 0.96; P<.01).
Conclusions: Correlation and concordance between supervised and postal administration of the MiniAQLQ and ACQ are very high. Users may confidently choose the mode of administration most appropriate to their needs.