Study's conclusions are premature

EDITOR—Premaratne et al amassed an impressive amount of data in the Greenwich asthma study,1 but their outcome measures were unlikely to be able to detect an effect of their intervention. We think that they may have had an unreal expectation of the impact of the intervention in primary care, perhaps reflecting the absence of primary care researchers in the study team.

Designing large scale studies to test guidelines and educational interventions is not easy, particularly in inner city general practice.2 When testing whether nurses improve the care of patients with asthma in general practice, appropriate primary outcomes are measures of asthma control and health service use in the patients who consulted with the nurses rather than in the wider population of asthmatic patients. To judge the efficacy of the study nurses on their lack of effect on patients they did not see seems harsh, although asking asthmatic patients to attend review sessions is arguably part of their role. Though the mean square root of quality of life of the total asthmatic population is clearly an important (secondary) outcome, its importance …