Psychometric properties of a specific quality of life questionnaire in angina pectoris patients.

This paper describes the psychometric properties of the French version of the APQLQ (Angina Pectoris Quality of Life Questionnaire), that is to say, scaling assumptions, reliability and validity. This disease-specific Swedish questionnaire provides a global score as well as four subscores measuring physical activities, somatic symptoms, emotional distress, and life satisfaction. The French version was produced according to the forward-backward translation methodology. In a cross-sectional study, 183 coronary patients filled out the APQLQ and the MOS (Medical Outcomes Study) SF-36; 170 sent it back; the rate of missing data was low (1.3%). The factorial structure and the high level of inter-scale correlations (> 0.60) suggested that the APQLQ measured one global concept rather than separate domains. The multitrait analysis identified one problematic item correlated strongly with all domains. The internal consistency was good (alpha Cronbach > 0.70). The correlations with the SF-36 scales were consistent with what was expected. The distribution of the scores of the APQLQ according to the clinical severity of Angina Pectoris (AP) was as hypothesized: the more severe the AP, the more impaired the Quality of Life. The score significantly discriminated between symptomatic (n = 110) and asymptomatic patients (n = 60) except for the emotional distress scale (p = 0.14). We recommend to analyze the French APQLQ as an index rather than as a profile. Its reliability, concurrent and clinical validity allowed its use in clinical trials.