Concordance between clinician- and 2016 criteria-based diagnoses of fibromyalgia

The Fibromyalgia Survey Diagnostic Criteria-2016 (FSD-2016 criteria) were recently recommended for both clinical and research purposes. The present study aims to examine whether there is concordance between clinician-based and FSD-2016 criteria-based diagnoses of FM, and secondly, to examine how the illness severity and physical function relate to the criteria-based diagnosis among patients referred to a rheumatism hospital.

Participants with a clinician-based diagnosis of FM were included consecutively when referred to a patient education programme for patients with FM. Illness severity was assessed with the Fibromyalgia Survey Questionnaire (FSQ). Based on the FSQ, the fulfilment of the FSD-2016 criteria was evaluated. Physical function was assessed using the Fibromyalgia Impact Questionnaire (FIQ) function scale and self-reported employment status.

The sample included 130 patients (84% women) from 20 to 66 years of age. Eighty-nine per cent met the FSD-2016 criteria, and 44% of the patients were fully or partially employed. Great variability in illness severity was seen irrespective of employment status. There was an association between illness severity and physical function (r=0.4, p<0.001). For 95% of the patients, the FSQ illness severity scores classify as severe or very severe, and even for those not fulfilling the diagnostic criteria the scores were moderate and severe.

There was relatively high agreement between clinician- and criteria-based diagnoses. The illness severity overlapped irrespective of different employment status and fulfilment of FSD-2016 criteria.