The relationship between performances on neuropsychological symptom validity testing and the MCMI-III in patients with fibromyalgia

Fibromyalgia is a disorder that frequently presents with both cognitive complaints and psychiatric symptoms. This study investigated the association between Symptom Validity Test (SVT) performance and psychiatric symptoms as measured by the Millon Clinical Multiaxial Inventory-III (MCMI-III), a common measure of psychopathology. A total of 72 fibromyalgia patients at a tertiary care clinic completed the MCMI-III, an embedded cognitive symptom validity test (Reliable Digit Span), and a stand-alone cognitive symptom validity test (the Word Memory Test or Test of Memory Malingering). Of these patients, 21% failed a stand-alone SVT, whereas an additional 15% failed both a stand-alone and embedded SVT. Individuals who failed both stand-alone and embedded cognitive SVTs had higher scores on a number of MCMI-III personality subscales and had elevated scores on MCMI-III modifying indices compared to individuals who passed cognitive SVTs. Moreover, SVT performance was significantly correlated with multiple MCMI-III scores, including modifying indices, as well as the somatoform, depression, and anxiety subscales. In sum, cognitive and psychological symptom validity scores were significantly related. Given the new emphasis on cognitive complaints as part of the fibromyalgia diagnostic criteria, neuropsychological evaluation of both cognitive and psychological symptom validity should be a part of a comprehensive diagnostic assessment.