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Towards evidence based medicine for paediatricians
  1. Bob Phillips
  1. Centre for Evidence-based Medicine, Cairns Library, John Radcliffe Hospital, Oxford OX3 9DU, UK; bob.phillips{at}doctors.org.uk

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In order to give the best care to patients and families, paediatricians need to integrate the highest quality scientific evidence with clinical expertise and the opinions of the family.1Archimedes seeks to assist practising clinicians by providing “evidence based” answers to common questions which are not at the forefront of research but are at the core of practice. They are based on an original format from the Journal of Accident and Emergency Medicine.2

A word of warning. These best evidence topic summaries (BETs) are not systematic reviews, though they are as exhaustive as a practising clinician can produce. They make no attempt to statistically aggregate the data, nor search the grey, unpublished literature. What Archimedes offers are practical, best evidence based answers to practical, clinical questions.

Each topic follows the same format. A description of the clinical setting is followed by a structured clinical question. (These aid in focusing the mind, assisting searching,3 and gaining answers.4) A brief report of the search used follows—this has been performed in a hierarchical way, to search for the best quality evidence to answer the question.5 A table provides a summary of the evidence and key points of the critical appraisal. For further information on critical appraisal, and the measures of effect (such as number needed to treat, NNT), books by Sackett6 and Moyer7 may help. A commentary is provided to pull the information together, and for accessibility, a box provides the clinical bottom lines.

Readers wishing to submit their own questions—with best evidence answers—are encouraged to read the Instructions for Authors at http://www.archdischild.com. Three topics are covered in this issue of the journal.

  • Albumin infusion in hypoalbuminaemic children with oncological disease

  • Magnesium sulphate in paediatric status asthmaticus

  • Chiropractic in infantile colic

The good, the bad, and the unhelpful

How can we quantify the likely benefits and harms of treatments? For each treatment we have, there is a series of outcomes; we can calculate the “number needed to treat” (NNT) for good outcomes and “number needed to harm” (NNH) for adverse events. For antibiotic treatment of otitis media, there is an NNT ∼7 to prevent pain at 48 hours, and an NNH ∼7 to produce a rash, vomiting, or diarrhoea.

Does the simple equivalence of good and bad outcomes mean that the treatment has no overall effect? To make a balanced assessment you should take into account the severity of the outcome. (If the treatment had the effect of preventing death in 1 of 50 cases, but produced vomiting in 1 of 10 cases, it this a treatment which is five times as bad as good?) The weighing of one outcome against another can more formally assess this. The assessment is the “likelihood of being helped over harmed” or LBHH: LBHH = NNT/(NNH × how much worse bad outcome is over good)

For example, if a parent believed “vomiting, rash, or diarrhoea” is half as bad as “pain at 48 hours”, the LBHH would be 7/(7 × 0.5) = 2. (Antibiotics for otitis media are considered twice as good as bad.) This approach can be used to personalise the evidence to the patient, and make more transparent the process of evidence based decision making.

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