Predictive value of a simple asthma morbidity index in a general practice population

Background. There is a need in primary care for simple asthma outcome measu res that are valid in terms of their relationship with lung function and ca pable of predicting those patients for whom additional management is indica ted. Aim. To assess the predictive validity of a revised asthma morbidity index in United Kingdom (UK) general practice. Method. Morbidity index and peak flow rate data were gathered from nine gen eral practices over a three-month period. Two postal questionnaire surveys, one year apart, were conducted in one Tyneside general practice. Morbidity index data from 570 asthmatic patients were gathered in the first survey a nd used to predict morbidity over the next year. Results. For 120 responders with low morbidity, mean peak flow as a percent age of the predicted Value was 91% (SD = 21%); for 91 responders with mediu m morbidity, the per centage was 77% (SD = 21%); and for 90 responders with high morbidity, it was 63% (SD = 29%). Fifty-seven per cent of the morbidi ty index categories remained unchanged after 72 months. The relative risks of high morbidity for having any acute asthma attacks, more than four attac ks, and needing oral steroids during a one year period were 2.88 (CI = 1.87 to 4.43), 2.52 (Cl = 1.84 to 3.44) and 2.38 (Cl = 1.70 to 3.33) respective ly. Conclusion. The revised morbidity index is a simple and valid tool for the opportunistic surveillance of asthma in primary care.