Table 1.2Levels of evidence for studies of the accuracy of diagnostics tests5

LevelType of evidence
IaSystematic reviews (with homogeneity)a of level-1 studiesb
IbLevel-1 studiesb
IILevel-2 studiesc; systematic reviews of level-2 studies
IIILevel-3 studiesd; systematic reviews of level-3 studies
IVConsensus, expert committee reports or opinions and/or clinical experience without explicit critical appraisal; or based on physiology, bench research or ‘first principles’
a

Homogeneity means there are no or minor variations in the directions and degrees of results between individual studies that are included in the systematic review.

b

Level-1 studies are studies that use a blind comparison of the test with a validated reference standard (gold standard) in a sample of patients that reflects the population to whom the test would apply.

c

Level-2 studies are studies that have only one of the following:

  • narrow population (the sample does not reflect the population to whom the test would apply)
  • use a poor reference standard (defined as that where the ‘test’ is included in the ‘reference’, or where the ‘testing’ affects the ‘reference’)
  • the comparison between the test and reference standard is not blind

d

Level-3 studies are studies that have at least two or three of the features listed above.

From: 1, Scope and methodology

Cover of Urinary Tract Infection in Children
Urinary Tract Infection in Children: Diagnosis, Treatment and Long-term Management.
NICE Clinical Guidelines, No. 54.
National Collaborating Centre for Women's and Children's Health (UK).
London: RCOG Press; 2007 Aug.
Copyright © 2007, National Collaborating Centre for Women’s and Children’s Health.

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