Substantial Agreement Between Classification Criteria for Fibromyalgia, With ACR 2011 Criteria Performing Best

Researchers compared the 3 diagnostic criteria and assessed the performance of an additional set of criteria in the diagnosis of fibromyalgia.

There is considerable agreement between the 3 criteria-based diagnoses of  fibromyalgia (FM) syndrome — the 2011 American College of Rheumatology criteria (ACR 2011 Cr), the ACR 2016 criteria (ACR 2016 Cr), the Analgesic, Anesthetic, and Addiction Clinical Trial Translations Innovations Opportunities and Networks (ACTTION)-American Pain Society Pain Taxonomy criteria (AAPT Cr) — and the modified Fibromyalgia Assessment Status (FAS 2019 modCr), according to study results published in Rheumatology (Oxford).

In this study, the researchers aimed to compare the concordance of the 3 diagnostic criteria for FM, namely the ACR 2011 Cr, the ACR 2016 Cr, and the ACTTION-AAPT Cr, and investigate the performance of the additional set of criteria, the FAS 2019 modCr, in the diagnosis of FM syndrome; the FAS 2019 modCr are an updated version of the FAS questionnaire with a simplified scoring system.

To evaluate the 4 proposed criteria in FM, the researchers enrolled a total of 732 participants (mean age, 52.08 years), among whom 405 had FM (94.1% women), and 327 (89.3% women) had other common chronic pain problems, from the practices of 2 rheumatologists in Italy between June 2017 and May 2019. Sensitivity, specificity, correct classification, and positive likelihood (LR+) were determined vs the clinical diagnosis of FM. Researchers analyzed discriminant validity to identify data from patients with FM and non-FM, with receiver operating characteristic curve (ROC) analysis for the FAS 2019 modCr.

Results of the study revealed that compared with the clinical diagnosis of FM, the sensitivity, specificity, correct classification, and LR+ were 79.8%, 91.7%, 85.1%, and 9.66 for the ACR 2011 Cr; 78%, 90.5%, 83.6%, and 8.23 for the ACR 2016 Cr; and 73.8%, 91.7%, 81.8%, and 8.94 for the AAPT Cr, respectively. In comparison, the FAS 2019 modCr, provided a maximal diagnostic accuracy with a score of ≥20 (Youden index), a sensitivity of 84.2%, specificity of 89.0%, and LR+ of 7.65.

Overall, although the ACR 2011 Cr seemed to be the best performing criteria and the AAPT Cr the worst performing criteria in terms of percentage of correct classification, there was considerable agreement between all the criteria-based diagnoses of FM.

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Study limitations included the cross-sectional evaluation, recruitment of participants from a single center, the variability in diagnostic judgment among clinicians, and the incomplete use of analysis of ROC curves among the criteria.

Researchers concluded, “As regards the FAS 2019 modCr, based on patients’ assessment of fatigue, sleep disturbances, and pain evaluated on 19 nonarticular sites, the operating characteristics are similar to those of more validated instruments…, with somewhat better ease-of-use, and could be used for diagnosis and follow-up of patients [with] FM.”


Salaffi F, Di Carlo M, Farah S, et al. Diagnosis of fibromyalgia: comparison of the 2011/2016 ACR and AAPT criteria and validation of the modified Fibromyalgia Assessment Status [published online March 24, 2020]. Rheumatology (Oxford). doi:10.1093/rheumatology/keaa061