June 29, 2015
2 min read

Polysymptomatic distress scale may be useful in diagnosing fibromyalgia

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A polysymptomatic distress scale comprising the sum of the Widespread Pain Index and the Symptom Severity Scale, components of the American College of Rheumatology 2010 criteria, may be a useful diagnostic method for patients with and without fibromyalgia, according to research by Frederick Wolfe, MD, and colleagues.

The researchers identified 2,732 patients with rheumatoid arthritis (RA) in the National Databank for Rheumatic Diseases, which included data from questionnaires administered in 2014. Patients with RA were the choice sample group due to the higher prevalence of fibromyalgia (FM) compared with the general population and as a means to distinguish RA from FM to test the validity of the polysymptomatic distress scale (PSD) as a diagnostic tool.

Frederick Wolfe

A diagnosis of FM was based on the modified American College of Rheumatology (ACR) 2010 criteria by summing the total scores from the Widespread Pain Index (WPI) with a 0 to 19 scale for nonarticular pain and the Symptom Severity Scale (SSS), which has a scale of 0 to 12 for fatigue, sleep disturbance and cognitive problems.

The researchers determined threshold values for the PSD by first examining the location and range of the lowest or “normal” classification after reviewing literature about the distribution of PSD scores among the general population, in which, 68% of respondents had a PSD score of 3 or lower; hence, a score between 0 and 3 was deemed the “none” classification. Scores of 4 to 7 were considered “mild,” and scores of 8 to 11 were considered “moderate” cases. A score of at least 12 was defined as the threshold for a fibromyalgia diagnosis, with scores of 12 to 19 labeled as “severe” and scores of 20 to 31 labeled as “very severe.”

The results were compared with the WPI in the ACR 1990 FM criteria. Pain and global severity were assessed using a 0 to 10 VAS, and functional status was measured with the Health Assessment Question-Disability Index (HAQ). The physical and mental component summary scores from the Medical Outcomes Study SF-36 were calculated, and other questionnaires were used to evaluate depression, anxiety and other variables. PSD scores were also compared with data from patients who met ACR 2010 criteria for FM.

Reports of increasing WPI increased from 0% in the none group, to 18% in the mild group, 57.5% in the moderate group, 87% in the severe group, and up to 100% in the very severe group.

Scores of 12 or higher tended to correlate with ACR criteria, but not all patients with scores above 12 met ACR criteria for FM, due to lower somatic symptom scores on the PSD, which may be a limitation of the method, according to the researchers.

“The advantages of the criteria / PSD scale as a measure of severity are several. First, the scale is simple to use and to score and is increasingly being used in patients with FM,” the researchers wrote. “Second, it provides a useful overall measure of FM severity. Finally, it can be used in all patients, not just those with FM — particularly because what is being measured with PSD is a universal quantity, not a score just used for FM.” – by Shirley Pulawski

Disclosure: The researchers report no relevant financial disclosures.