Are embedded validity indices equivalent to free-standing symptom validity tests?

Symptom validity assessment is an important part of neuropsychological evaluation. There are currently several free-standing symptom validity tests (SVTs), as well as a number of empirically derived embedded validity indices, that have been developed to assess that an examinee is putting forth an optimal level of effort during testing. The use of embedded validity indices is attractive since they do not increase overall testing time and may also be less vulnerable to coaching. In addition, there are some instances where embedded validity indices are the only tool available to the neuropsychological practitioner for assessing an examinee's level of effort. As with free-standing measures, the sensitivity and specificity of embedded validity indices to suboptimal effort varies. The present study evaluated the diagnostic validity of 17 embedded validity indices by comparing performance on these indices to performance on combinations of free-standing SVTs. Results from the current medico-legal sample revealed that of the embedded validity indices, Reliable Digit Span had the best classification accuracy; however, the findings do not support the use of this embedded validity index in the absence of free-standing SVTs.