Clustered randomised trial of an intervention to improve the management of asthma: Greenwich asthma study.

OBJECTIVES To evaluate the effectiveness of an asthma resource centre in improving treatment and quality of life for asthmatic patients. DESIGN Community based randomised controlled trial. SETTING 41 general practices in Greenwich with a practice nurse. SUBJECTS All registered patients aged 15-50 years. INTERVENTION Nurse specialists in asthma who educated and supported practice nurses, who in turn educated patients in the management of asthma according to the British Thoracic Society's guidelines. MAIN OUTCOME MEASURES Quality of life of asthmatic patients, attendance at accident and emergency departments, admissions to local hospitals, and steroid prescribing by general practitioners. RESULTS Of 24 400 patients randomly selected and surveyed in 1993, 12 238 replied; 1621 were asthmatic of whom 1291 were sent a repeat questionnaire in 1996 and 780 replied. Of 24 400 patients newly surveyed in 1996, 10 783 (1616 asthmatic) replied. No evidence was found for an improvement in asthma related quality of life among newly surveyed patients in intervention practices compared with control practices. Neither was there evidence of an improvement in other measures of the quality of asthma care. Weak evidence was found for an improvement in quality of life in intervention practices among asthmatics registered with study practices in 1993 and followed up in 1996. Neither attendances at accident and emergency departments nor admissions for asthma showed any tendency to diverge in intervention and control practices over the study period. Steroid prescribing rates rose steadily during the study period. The average annual increase in steroid prescribing was 3% per year higher in intervention than control practices (95% confidence interval -1% to 6%, P=0.10). CONCLUSIONS This model of service delivery is not effective in improving the outcome of asthma in the community. Further development is required if cost effective management of asthma is to be introduced.