On diagnosing rare disorders rarely: appropriate use of screening instruments

J Child Psychol Psychiatry. 1999 Feb;40(2):287-90.


The main aim of this study was to determine whether child mental health professionals who regularly use questionnaires to screen for mental disorders know that these questionnaires have a low predictive value when the base rate of a disorder is low. The study was based on a representative sample of professionals who used questionnaires regularly to screen for mental disorders. They were set a problem in which a clinic sample was screened with a questionnaire that, at a certain cut-point, had 80 % sensitivity and 80 % specificity, and in which the true base rate of disorder was 10%. Only 10% (5/48) of respondents answered correctly that just 30 % of individuals who scored above this cut-point would actually have the disorder and more than half of respondents believed that 80 % would have the disorder. Both users and designers of questionnaires need to be more aware of and explicit about their drawbacks as screens for mental disorders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child
  • Child Health Services / standards*
  • Child Psychiatry / standards
  • England
  • Health Care Surveys
  • Humans
  • Incidence
  • Mental Disorders / diagnosis*
  • Mental Disorders / epidemiology
  • Mental Health Services / standards*
  • Professional Practice / standards
  • Professional Practice / statistics & numerical data*
  • Psychiatric Status Rating Scales / standards
  • Psychiatric Status Rating Scales / statistics & numerical data*
  • Reference Values
  • Sensitivity and Specificity
  • Surveys and Questionnaires / standards
  • Surveys and Questionnaires / statistics & numerical data*