The Editors welcome topical correspondence from readers relating to articles published in the Journal. Responses should be sent electronically via the BJS website (www.bjs.co.uk). All letters will be reviewed and, if approved, appear on the website. A selection of these will be edited and published in the Journal. Letters must be no more than 250 words in length.
Meta-analysis and systematic review of the relationship between volume and outcome in abdominal aortic aneurysm surgery (Br
J Surg 2007; 94: 395-403) Sir Holt et al. have written an interesting paper on the inverse relationship between volume and outcome for (elective) abdominal aortic aneurysm repair.
Whereas two recent systematic reviews on the same topic decided that there were too few studies for a sensible pooling of data 1,2 , the authors estimated the excess risk of mortality by calculating odds ratios using only the studies that provide raw data, which is certainly valuable. However, the analysis is misleading, as several studies on the same set of patients were included more than once; refs 43 and 41, refs 7 and 25, and refs 36 and ref. 53, respectively. In addition, ref. 8 included 11 856 patients instead of 13 887. Data extraction by two independent investigators probably could have avoided this problem.
As several studies reported multiple thresholds it would have been interesting to do a sensitivity analysis by varying the threshold for high and low volume. We agree that there is an inverse relationship between volume and outcome, though not necessarily significant and important, and certainly not at a threshold of 43 operations annually (although the authors leave the reader to draw this conclusion).