Background and objective: The aim of this study was to assess the measurement properties of the Spanish version of Asthma Control Questionnaire (ACQ) when FEV1 item in the original version (ACQ-FEV1) is substituted by peak expiratory flow rate (ACQ-PEF) and when the lung function item is omitted (ACQ-wLF).
Material and method: and 607 patients were enrolled in this study. Three study visits were carried out: at baseline, 2, and 6 weeks later. Validity, reliability and sensitivity to change of both ACQ versions were calculated.
Results: ACQ-PEF and ACQ-wLF had a correlation coefficient of 0.38 and 0.39 with no exacerbations. Both symptoms improvement and a better perception of asthma control, both by physicians and patients, were significantly related ro better scores in both versions (P <0.01). Cronbach a of ACQ-PEF and ACQ-wLF were 0.83 and 0.87, respectively. Intraclass correlation coefficients of both ACQ-PEF and ACQ-wLF were 0.9 and 0.87. Mean scores of all ACQ versions (ACQ-FEV1, ACQ-PEF and ACQ-wLF) were 1.31 (1), 1.34 (1) and 1.14 (1.1), respectively, being all differences statistically significant P < or = 0.003).
Conclusions: Replacement of FEV1 by PEF, or its elimination, does not alter the measurement properties of the ACQ questionnaire. Use of ACQ simplified versions is recommended only for investigational purposes, without combining in the same analysis scores obtained with different versions of the questionnaire.