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

There is a need in primary care for simple asthma outcome measures that are valid in terms of their relationship with lung function and capable of predicting those patients for whom additional management is indicated.

To assess the predictive validity of a revised asthma morbidity index in United Kingdom (UK) general practice.

Morbidity index and peak flow rate data were gathered from nine general 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 and used to predict morbidity over the next year.

For 120 responders with low morbidity, mean peak flow as a percentage of the predicted value was 91% (SD = 21%); for 91 responders with medium morbidity, the percentage was 77% (SD = 21%); and for 90 responders with high morbidity, it was 63% (SD = 29%). Fifty-seven per cent of the morbidity index categories remained unchanged after 12 months. The relative risks of high morbidity for having any acute asthma attacks, more than four attacks, and needing oral steroids during a one year period were 2.88 (CI = 1.87 to 4.43), 2.52 (CI = 1.84 to 3.44) and 2.38 (CI = 1.70 to 3.33) respectively.

The revised morbidity index is a simple and valid tool for the opportunistic surveillance of asthma in primary care.