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Fibromyalgia: can one distinguish it from simulation? An observer-blind controlled study.
I Khostanteen1, E R Tunks, C H Goldsmith
1Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada.
The Journal of Rheumatology
|November 28, 2000
Summary
Researchers assessed the accuracy of diagnosing fibromyalgia (FM) in patients versus healthy individuals and those simulating the condition. While examiners achieved 80% accuracy, distinguishing between FM and simulators remains challenging.
Area of Science:
- Rheumatology
- Clinical Diagnosis
- Psychosomatic Medicine
Background:
- Fibromyalgia (FM) diagnosis relies on clinical criteria, but distinguishing genuine cases from malingering can be difficult.
- Previous studies have explored the reliability of diagnostic methods, but few have specifically investigated motivated simulation under blinded conditions.
Purpose of the Study:
- To evaluate the diagnostic accuracy and reliability of identifying fibromyalgia (FM) in patients compared to healthy controls and financially motivated simulators.
- To assess the effectiveness of tender point counts and illness behavior ratings in differentiating these groups.
Main Methods:
- A randomized controlled trial involving 8 female subjects with chronic FM and 19 healthy female volunteers.
- Volunteers were randomized into a 'simulator' group (paid to feign FM) or a 'normal control' group.
- Blinded examiners assessed tender points, control points, and illness behavior; grip strength and self-rated pain were also measured.
Main Results:
- Tender point counts significantly discriminated between the three groups (FM, simulators, normal controls).
- Examiners achieved 80% accuracy in distinguishing FM from simulators and normals, with a significant kappa value of 0.69.
- However, simulators were misidentified as FM in 33% of cases, and FM patients were misidentified as simulators in 20% of cases.
Conclusions:
- Blinded examiners can distinguish chronic FM, normal individuals, and motivated simulators with 80% accuracy using established criteria and bedside observations.
- Tender point counts demonstrated good agreement and reliability.
- The study does not offer a definitive 'test for malingering,' as a significant minority of both simulators and FM patients were misidentified.