Quality of life in asthma:: reliability and validity of the short form generic questionnaire (SF-36) applied to the population of asthmatics in a public health area

OBJECTIVE: To analyze the reliability and validity of the short form of the generic quality of life scale (SF-36) when used with our asthmatic patients. METHODS: Two hundred nineteen adults with asthma of any etiology and without limits on sex, type or severity of asthma who were being treated at 10 health clinics (Madrid, Area 2) filled in the questionnaire. Reliability was calculated by an analysis of internal consistency and validity by studying the correlation among certain variables (patient age, age of onset, PEF, FEV1 and severity according to consensus criteria) and the analysis of differences on each of the dimensions encompassing such variables. RESULTS: The highest score (best quality of life) was observed in the dimension of role limitations due to emotional problems (80 +/- 37) and the lowest was seen for perception of general health (50.4 +/- 24). The percentage of patients with the lowest scores ranged from 0 to 5.8% and the percentage with the highest scores ranged from 0.4 to 19.8%. The Cronbach alpha coefficient was greater than 0.7 (range 0.77 +/- 0.80). Mean scores related to level of severity were significantly better for men than for women on only three dimensions and for mild and moderate severity groups. All dimensions except role limitations due to emotional and physical problems were significantly related to FEV1%. CONCLUSION: The reliability and validity of the Spanish version of the SF-36 questionnaire is satisfactory when applied to asthmatic patients, making it an appropriate way to assess quality of life.