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We read with interest the report by Weigel et al1 on the outcome of contemporary surgery for chronic subdural haematoma, and commend the authors for attempting to review such an extensive and diverse range of publications. The paper ably demonstrates the lack of quality evidence for the management of this common condition. However, we are concerned about the description of the paper as “evidence based”. Exclusion criteria were broad, and fewer than 5% of papers found in the Medline literature search were included in the final analysis. Correspondence with the original authors for further data or clarification is an acceptable and expected part of evidence based analysis, and would have increased paper and patient numbers significantly.2,3 The data examined do not appear to have been paired, as age and comorbidity will have dramatic effects on outcome, irrespective of surgical technique. In this context, unpaired univariate statistical analysis is unable to produce meaningful significance. Further detracting factors include limited search procedures, absent quality assessment and weightings of individual papers, exclusion of premorbid status in deciding success rates, and a burr hole diameter defined as up to 3 cm—classified by many neurosurgeons as a craniotomy. We are concerned that, on a less careful reading, this paper could serve as a reference in the realm of “evidence based medicine”, when it fails to adhere to most criteria of good evidence based medicine.
We appreciate the comments by Brodbelt and Warnke on our recent evidence based review on the outcome of contemporary surgery for chronic subdural haematoma. We completely agree with them that one of the surprising findings of our review was that there is indeed a paucity of methodological good studies on the surgical management of one of the most common entities seen in neurosurgical clinical routine. As most studies we reviewed were retrospective and some relied solely on expert opinions, it was not possible to achieve our initial goal of carrying out a meta-analysis of the data. Nevertheless, it was possible to scrutinise the available data with the armamentarium of evidence based methodology. It is obvious, however, that the conclusions to be drawn depend on the primary data. The proposals of the quorum conference cited are concerned primarily with improving the quality of meta-analysis of randomised clinical trials.
Good clinical practice is not necessarily good evidence based medicine. There are many problems in the methodology of evidence based medicine itself, and the validity of its recommendations are increasingly being questioned. Finally, the key to understanding an article or a review is always the critical appraisal of reader themselves. This is no less important for meta-analyses or evidence based reviews. Even to the “less careful reading” it should be clear that our review provides an inventory of the current situation but that a critical analysis of the data does not allow one to go further and specify guidelines. We hope that our review will stimulate our colleagues to provide high quality evidence in the future. There are many questions to be answered.
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