Reducing the probability of false positives in malingering detection of Social Security disability claimants.

The Symptom Validity Scale (SVS) for low-functioning individuals (Chafetz, Abrahams, & Kohlmaier, 2007) employs embedded indicators within the Social Security Psychological Consultative Examination (PCE) to derive a score validated for malingering against two criterion tests: Test of Memory Malingering (TOMM) and Medical Symptom Validity Test (MSVT). When any symptom validity test is used with Social Security claimants there is a known rate of mislabeling (1-specificity), essentially calling a performance biased (invalid) when it is not, also known as a false-positive error. The great costs of mislabeling an honest claimant necessitated the present study, designed to show how multiple positive findings reduce the potential for mislabeling. This study utilized a known-groups design to address the impact of using multiple embedded indicators within the SVS on the diagnostic probability of malingering. Using four SVS components, Sequence, Ganser, and Coding errors, along with Reliable Digit Span (RDS), the positive predictive power was computed directly or by the chaining of likelihood ratios. The posterior probability of malingering increased from one to two to three failed indicators. With three failed indicators, there were essentially no false positive errors, and the total SVS score was in the range consistent with Definite Malingering, as shown in Chafetz et al. (2007). Thus, in a typical PCE when an examiner might have only a few embedded indicators, more confidence in a diagnosis of malingering might be obtained with a finding of multiple failures.