Thresholds and accuracy in screening tools for early detection of psychopathology

• DOI: 10.1111/jcpp.12442
• Publication Date: 2015-06-19T08:57:29Z
• Authors: R. Christopher Sh...; James C. Benneyan; Ivy Giserman Kiss; Margaret J. Brigg...; William Copeland; Alice S. Carter
• Keywords: Psychiatric Status Rating Scales; Adolescent; Psychometrics; Mental Disorders; 05 social sciences; Sensitivity and Specificity; 6. Clean water; 03 medical and health sciences; Early Diagnosis; 0302 clinical medicine; Child, Preschool; Humans; 0501 psychology and cognitive sciences; Child

BackgroundThe accuracy of any screening instrument designed to detect psychopathology among children is ideally assessed through rigorous comparison to ‘gold standard’ tests and interviews. Such comparisons typically yield estimates of what we refer to as ‘standard indices of diagnostic accuracy’, including sensitivity, specificity, positive predictive value (PPV), and negative predictive value. However, whereas these statistics were originally designed to detect binary signals (e.g., diagnosis present or absent), screening questionnaires commonly used in psychology, psychiatry, and pediatrics typically result in ordinal scores. Thus, a threshold or ‘cut score’ must be applied to these ordinal scores before accuracy can be evaluated using such standard indices. To better understand the tradeoffs inherent in choosing a particular threshold, we discuss the concept of ‘threshold probability’. In contrast toPPV, which reflects the probability that a child whose scorefalls at or abovethe screening threshold has the condition of interest, threshold probability refers specifically to the likelihood that a child whose scoreis equal toa particular screening threshold has the condition of interest.MethodThe diagnostic accuracy and threshold probability of two well‐validated behavioral assessment instruments, the Child Behavior Checklist Total Problem Scale and the Strengths and Difficulties Questionnaire total scale were examined in relation to a structured psychiatric interview in three de‐identified datasets.ResultsAlthough both screening measures were effective in identifying groups of children at elevated risk for psychopathology in all samples (odds ratios ranged from 5.2 to 9.7), children who scored at or near the clinical thresholds that optimized sensitivity and specificity were unlikely to meet criteria for psychopathology on gold standard interviews.ConclusionsOur results are consistent with the view that screening instruments should be interpreted probabilistically, with attention to where along the continuum of positive scores an individual falls.