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The benefits of a strong hypothesis for retrospective research
  1. Tom Harcourt-Brown, MA, VetMB, CertVDI, DipECVN, MRCVS
  1. Langford Veterinary Services, University of Bristol, Lower Langford, North Somerset, BS40 5DU, UK
  1. E-mail: tom.harcourt-brown{at}

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EVIDENCE-based medicine is a philosophical doctrine that can be used to guide clinical decision making. At its simplest, it is the belief that a clinical decision should be made based upon the best available evidence married with clinical expertise (Sackett and others 1996). One of its central tenets is that there is a hierarchy (or pyramid) of evidence (Table 1). This can be used as a way of putting research into context when conflicting findings exist.

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Example of an evidence hierarchy used in medical and veterinary research. The various types of study are listed in order of descending weight of evidence

One example of when a hierarchy of evidence can be useful in veterinary medicine is when considering the benefit of prophylactic intervertebral disc fenestration to prevent recurrence of disc extrusion in dogs. A relatively large number of papers present retrospective analyses of recurrence rates in several hundred dogs that either had, or did not have, prophylactic fenestration performed.

From this large amount of data, it could be assumed that the recommendation as to whether to perform fenestration or not would be clear. It is not. In terms …

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