Endgames Statistical Question

Generalisation and extrapolation of study results

BMJ 2013; 346 doi: https://doi.org/10.1136/bmj.f3022 (Published 10 May 2013) Cite this as: BMJ 2013;346:f3022
  1. Philip Sedgwick, reader in medical statistics and medical education
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}sgul.ac.uk

Researchers assessed the effectiveness of peritendinous autologous blood injections in patients with mid-portion Achilles tendinopathy. A randomised double-blind controlled trial was performed. The intervention consisted of two unguided peritendinous injections with 3 mL of the patient’s whole blood given one month apart. The control group had no substance injected (needling only). Participants in both groups carried out a standardised and monitored 12 week eccentric calf training programme.1

In total, 53 adults (mean age 49 years, 53% men) were recruited from a sports medicine clinic in New Zealand. Inclusion criteria included age over 18 years and presentation with first episode of mid-portion Achilles tendinopathy. Symptoms had to be present for at least three months, with the diagnosis confirmed by diagnostic ultrasonography.

The primary outcome measure was change in symptoms and function from baseline to six months as assessed by the Victorian Institute of Sport Assessment-Achilles (VISA-A) score. Significant improvements in the VISA-A score were seen at six months in the intervention group (change in score 18.7, 95% confidence interval 12.3 to 25.1) and control group (19.9, 13.6 to 26.2). However, the overall effect of treatment …

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