Intended for healthcare professionals

Endgames Statistical question

Relative risks

BMJ 2010; 341 doi: (Published 28 July 2010) Cite this as: BMJ 2010;341:c3983
  1. Philip Sedgwick, senior lecturer in medical statistics1,
  2. Louise Marston, research statistician2
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London SW17 0RE
  2. 2Department of Primary Care and Population Health, University College London, London NW3 2PF
  1. p.sedgwick{at}

    Researchers assessed the effects of β lactam antibiotics prescribed in the community for acute respiratory tract infection on the prevalence of antibiotic resistant bacteria in an individual child. A total of 119 children with acute respiratory tract infection were recruited in primary care, of whom 71 received a β lactam antibiotic. A prospective cohort study design was used with follow-up at two and 12 weeks. Antibiotic resistance was assessed by the presence of the ICEHin1056 resistance element in up to four isolates of Haemophilus species, recovered from throat swabs at recruitment and follow-up.1

    At two weeks, 67% of children prescribed antibiotics had isolation of Haemophilus isolates possessing homologues of ICEHin1056, compared with 36% of those not prescribed antibiotics (relative risk = 1.9; 95% confidence interval: 1.2 to 2.9).

    Which …

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