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Evaluating Screening Tests for Dementia and Cognitive Impairment in a Heterogeneous Population in the Presence of Verification Bias

Published online by Cambridge University Press:  10 January 2005

Alan Donald  and
Linda Van Til
Alan Donald
Affiliation:
Donald Associates, Vancouver, British Columbia
Linda Van Til
Affiliation:
PEI Department of Health and Social Services, Charlottetown, Prince Edward Island.
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Abstract

This article reviews two potentially serious sources of error in the evaluation of screening tests, namely, verification bias and the influence of demographic covariates. It demonstrates how to deal with these problems statistically. Verification bias arises when not all subjects receive a definive diagnosis following a screening test. If only a small proportion of those who screen negative are sent for diagnosis, the calculated test sensitivity is an overestimate and the calculated specificity an underestimate. The methodology outlined in this article may be extended to psychological and medical screening tests in general.

Type
DERIVED VARIABLES FOR THE CSHA
Information
International Psychogeriatrics , Volume 13 , Issue S1 , February 2001 , pp. 203 - 214
Copyright
© 2001 International Psychogeriatric Association

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