The quality and quantity of randomised trials of surgical techniques is acknowledged to be limited. According to Peter McCulloch and colleagues, however, some aspects of surgery present special difficulties for randomised trials. In this article they analyse what these difficulties are and propose some solutions for improving the standards of clinical research in surgery

The improvement in the quality of clinical research in the past decade is to be welcomed, but it carries its own dangers. Some have extrapolated the advantages of the randomised controlled trial (RCT) into the dogma that it is the only valid method for comparing treatments,1 ignoring the difficulties that have hampered the use of RCTs in some disciplines. The RCT has theoretical advantages over other study designs, but experimental studies comparing treatment effect estimates in randomised and non-randomised studies have not consistently confirmed this, 2 3 ^w1-w3 and the superiority of RCTs should not therefore be accepted as axiomatic.

Small, poorly conducted RCTs are more likely to result when RCTs are difficult to conduct, and these may then be misleading because their design affords them unwarranted credibility. Surgery seems to be such an area. Until recently, most studies of operations were retrospective case series, with RCTs accounting for less than 10% of the total.^w4-w6 RCTs declined from 14% of research articles in the British Journal of Surgery in 1985 to 5% in 1992. 4 5 Treatments in general surgery are half as likely to be based on RCT evidence as treatments in internal medicine. 6 7 Methodological quality was poor in 56% of RCTs comparing cancer surgery techniques.8 Only 58% of these studies described satisfactory randomisation, and few significant outcome differences were found, probably because of type II statistical errors.

Why is surgery so deficient? Some of the obstacles militate against all …