Delay in fibromyalgia diagnosis and its impact on the severity and outcome: a large cohort study

Objectives: To evaluate the impact of the diagnostic delay on fibromyalgia (FM) severity. Methods: Data were retrospectively extracted from a large database of patients with FM belonging to the Italian Fibromyalgia Registry (IFR) residents on the Marche Region. The diagnosis of FM was formulated according to the 2016 American College of Rheumatology (ACR) criteria. The following information was obtained: time to diagnosis [categorised in early diagnosis (ED) if FM diagnosed within one year, late diagnosis (LD) if FM diagnosed more than 1 year but less than 5 years, and very late diagnosis (VLD) if FM diagnosed over 5 years from symptoms onset], revised Fibromyalgia Impact Questionnaire (FIQR), modified Fibromyalgia Assessment Status (FASmod), and Polysymptomatic Distress Scale (PDS) [consisting of the sum of Widespread Pain Index (WPI) and Symptom Severity Scale (SSS)]. Results: The study included 616 FM patients (92.2% female), with a mean disease duration of 6.46 (SD 4.14) years and a mean (SD) time to diagnosis of 3.45 (2.39) years. The ED group included 169 patients, the LD 320 patients, and the VLD 127 patients. Comparing the differences among groups, a significant difference in disease severity was observed in all the clinimetric indices in increasing the time to reach the diagnosis (p=0.000001): the median PDS scores were 13.36 (interquartile range [IQR] 7.00-20.00), 16.09 (IQR 9.00-22.00), and 23.00 (IQR 18.25-26.00) for ED, LD, and VLD, respectively. Conclusions: Delayed diagnosis is associated with poorer patient outcomes, including worsening severity.