Editorials Use of indirect standardisation is inappropriate

Performance league tables

BMJ 2002; 325 doi: https://doi.org/10.1136/bmj.325.7357.177 (Published 27 July 2002) Cite this as: BMJ 2002;325:177
  1. Andrew Rixom, specialist registrar in public health. (andrew.rixom@medix-uk.com)
  1. East Lincolnshire Primary Care Trust, Boston PE21 8QR

    Valid performance league tables cannot be formed from indirectly standardised indices.15 However, this methodology has been adopted for most of the performance indicators for NHS trusts that relate to outcomes, effectiveness, and access. This includes all the clinical indicators.6 Indirect standardisation is also used to compare general practitioners' prescribing.7

    As an illustration, the example in the box includes two study populations with identical category specific rates (these may be for age, ethnicity, or case mix, for example). Despite performing identically, they have two very different indirectly standardised ratios because of their different structures.

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    The inappropriate comparison of performance using indirect standardisation arises because of a common misconception about the standard that is being used. For indirect standardisation the study population itself is the standard, as this is the population to which the category specific reference rates are applied. Consequently, a different standard is …

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