Using decision theory to derive optimal cut‐off scores of screening instruments: an illustration explicating costs and benefits of mental health screening

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Abstract
This paper shows how decision theory can be used to determine optimal cut‐off scores on mental health screeners. The procedure uses (a) the costs and benefits of correct and erroneous decisions, and (b) the rates of correct and erroneous decisions as a function of the cut‐off score. Using this information, for each cut‐off point expected costs are calculated. The cut‐off point with the lowest expected costs is the optimal cut‐off score. An illustration is given in which the General Health Questionnaire is employed as a major depression screener. Optimal cut‐off points are determined for four different contexts: patients, health service providers, society, and mental health researchers. As in these four situations different costs are encountered, different optimal cut‐off points were found. Copyright © 2008 John Wiley & Sons, Ltd.