Are patients with chronic pain and fibromyalgia correctly classified by MMPI-2 validity scales and indexes?

Abstract

A study was designed to find out whether MMPI-2 validity scales and indexes differentiate between truefibromyalgia sufferers, patients with chronic organic pain and normal people, as well as whether they arecorrectly classified. 105 subjects participated in the study, 27 diagnosed with fibromyalgia and 44 withchronic organic pain and 34 were healthy people, who answered the MMPI-2 following standardinstructions. The results showed that fibromyalgia patients scored higher than the control group in the F,Fb, F-K, Fp, Ds, and FBS scales and indexes and that patients with chronic organic pain scored higher in theDs and FBS scales than the control group. The case study revealed that the F, Fb, F-K, Fp, Ds, and FBS scalesand indexes over-diagnose malingering in patients with fibromyalgia, both in comparison with the clinicalpopulation and with the normative group. Likewise, patients with chronic organic pain were overdiagnosedas malingerers by all the scales and indexes in comparison with the normative population andby the Fp and FBS scales in comparison with the clinical population. In addition, it was found that at leastone of the scales for measuring defensiveness –L, Wsd and Mp– classified 79.5% of the truly ill patients asfaking good. The implications for clinical and forensic practice are discussed, as well as for the definition ofdecision criteria and the (re)classification as true negatives of genuine cases classified as malingerers bythe malingering measuring scales and indexes.

Keywords

• MMPI-2
• Malingering
• Fibromyalgia
• Chronic pain