Background/Purpose:

Fibromyalgia Syndrome (FMS) is a multi-symptom disorder, characterized by somatic and cognitive manifestations, such as impaired working memory, executive function and attention (1,2).

The updated criteria for diagnosis of FMS (2016) recognize cognitive symptoms as a valid feature of the disease (3). These criteria use the Widespread Pain Index (WPI), a patient – reported tool reflecting the degree of pain dispersion, as well as the Symptom Severity Scale (SSS), reflecting a sum of accompanying symptoms. The SSS itself includes a cognitive index score (SSS-Cog), focused on cognitive manifestations experienced by FMS patients (4,5,6).

Previous studies have shown inconsistency in correlating subjective and objective cognitive impairment in FMS patients (7,8). This study aims to check the validity of the SSS-Cog, by evaluating the correlation between patient–reported cognitive symptoms of FMS and a battery of computerized normalized cognitive tests.

Methods:

FMS patients were recruited at a specialized FMS clinic. Participants were over 18 and diagnosed with FMS according to the 2010/2011 ACR diagnostic criteria (n=50, 86% women, 7% men). Secondary FMS patients were excluded.
NeuroTrax™ computerized cognitive assessment battery was used for evaluation of cognitive function, in addition to filling up the Fibromyalgia impact questionnaire (FIQ), WPI and SSS.

Depressive symptoms, which may alter cognition, were assessed by the Beck Depression Inventory (BDI)-II. Level of effort during cognitive testing was evaluated with the Test of Memory Malingering (TOMM).

A Spearman correlation coefficient was used to assess whether the SSS-Cog index correlated with performance on the computerized cognition tests. Further correlations were performed between the SSS-Cog and other questionnaires used in the study (WPI, FIQ, BDI-II).

Results:

The SSS-Cog results did not correlate with scores of the NeuroTrax™ cognitive assessment battery (rs= -.132, p= .361). Positive correlations were found between the SSS-Cog and the FIQ (rs= .438, p= .001), especially the pain measures utilized in it (VAS-pain, rs= .304, p= .032), as well as with the WPI (rs= .333, p= .018).
The lack of correlation between the SSS-Cog and objective cognitive performance persisted when excluding a subgroup of 8 low-effort participants with a TOMM score ≤45.
Age and BDI-II (depression) scores were also shown not to be confounding factors.

Conclusion:

There is a strong correlation between FMS patients’ subjective evaluations of cognitive impairment and self-measures of daily functioning, symptom intensity and experienced pain. However, a notable lack of correlation was found between patients’ self-reported cognitive impairment and objective cognitive scores, indicating that the SSS-cog does not reflect its self-proclaimed purpose – assessing cognitive impairment. These findings highlight the need for development of alternative tools in assessing cognitive impairment in FMS patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/validity-of-the-cognitive-index-of-the-symptom-severity-scale-sss-cog-in-assessing-cognitive-impairment-in-fibromyalgia-patients/