Intended for healthcare professionals

Endgames Statistical Question

Receiver operating characteristic curves

BMJ 2011; 343 doi: (Published 13 July 2011) Cite this as: BMJ 2011;343:d4302
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Section of Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}

Researchers investigated the performance of vital signs as screening tests for identifying brain lesions in patients with impaired consciousness on arrival at an emergency department. A total of 529 consecutive patients presenting with impaired consciousness, as assessed by a score of less than 15 on the Glasgow coma scale, were included. The vital signs of systolic and diastolic blood pressure plus pulse rate were recorded on arrival. All patients were followed until discharge, and the final diagnosis of a brain lesion was determined after brain imaging and neurological examination were performed. In total, 312 patients were diagnosed with a brain lesion.1

The performance of each vital sign as a screening tool for diagnosed brain lesions was evaluated separately. The measurement scale for each vital sign was categorised using equal sized strata. Each stratum for a vital sign was taken successively as the cut off between a “negative” and “positive” screening test result; all measurements with values greater than the categorised strata were considered a …

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