Secondary prevention in general practice: more details needed
I think that it is difficult to interpret the findings of the randomised trial of secondary prevention clinics for coronary heart disease (1) without details of the uptake of treatment. As pointed out in the accompanying Editorial (2), it is possible that the control group was contaminated - that is, there may have been an increase in the uptake of secondary prevention in both the intervention group and the control group. Cluster randomisation may have avoided the difficulty of contamination, although it would have had implications for the sample size calculation (3) potentially making the whole study impractical.
The authors have reported the effect of an intervention although it is not entirely clear what that intervention was. Was it the establishment of secondary prevention clinics, was it attendance at the clinics or was it a change in the uptake of proven treatments? This aside, Campbell et al. should be congratulated on their study as randomised trials in general practice are difficult (4) but essential to determine the real benefits of new treatments (5). I look forward to their next report
1. Campbell NC, Thain J, Deans GH, Ritchie LD, Rawles JM, Squair JL. Secondary prevention clinics for coronary heart disease: randomised trial of effect on health. BMJ 1998;316:1434-7.
2. van der Weijden T, Grol R. Preventing recurrent coronary heart disease. BMJ 1998;316:1400-1.
3. Underwood M, Barnett A, Hajioff S. Cluster randomisation: a trap for the unwary. British Journal of General Practice 1998;48:1089-90.
4. Pringle M, Churchill R. Randomised controlled trials in general practice. BMJ 1995;311:1382-3.
5. Hippisley-Cox J. Newly licensed drugs. Randomised controlled trials are needed in primary care before new drugs are licensed. BMJ 1997;314:604-5.
Lecturer in General Practice
Competing interests: No competing interests