Background Concomitant fibromyalgia syndrome is a common problem in ankylosing spondylitis (AS) and its recognition is important for optimal management of AS. There is a concern that validated tools of disease activity, function and patient reported outcomes in AS may be measuring fibromyalgia pain and symptoms in patients with concomitant AS and fibromyalgia.
Objectives We studied the relationship between the validated AS measures of disease activity, functional index, and markers of inflammation and ACR fibromyalgia diagnostic criteria.
Methods Study was approved by our IRB. We prospectively recruited 51 subjects ≥18 years of age with AS (meeting modified New York criteria with grade 3 or 4 sacroiliitis and high disease activity (BASDAI ≥3). Demographic and clinical data were collected and stored in Redcap data base. Various validated Questionnaires to assess disease, functional activity and patient reported outcomes in AS were administered to the patients. The frequency of FMS was determined using validated 2010 ACR diagnostic criteria for fibromyalgia . The patient met the fibromyalgia criteria if (i) widespread pain index (WPI) of ≥7 & symptom severity score (SS) ≥5 or WPI 3–6 & SS score ≥9,(ii) symptoms were present at a similar level for at least 3 months and (iii) the pain was not attributed to AS by the clinician. ESR and CRP was measured using routine laboratory methods. Descriptive analysis included continuous variables (the mean ± SD) and the categorical variables percentage. Linear regression analysis was performed to assess the association between BASDAI, BASMI, ASDAS, Rapid 3 and fibromyalgia status
Results There 34 males and 17 females with mean age of 49.8 ± 12.2; 30.6% African-Americans, 63.2% whites and 4.0% Asians, with 47.0% HLA-B27 positive, 29.4% negative and 23% unknown.18/47 (38.3%) have had acute anterior uveitis. 45% of the patients had been on TNF-α inhibitors. Mean BASDAI was 5.23 (±2.5); BASFI 4.7 (± 2.8); PGA 5.1 (±2.4); ASDAS-CRP 3.4 (±1.13); and RAPID 3 score 13.76 (± 7.21), ESR 22.4 mm/hr (±22.0) and CRP 1.3 mg/dl (±1.9).21 AS patients (41.2%) satisfied the diagnostic criteria of fibromyalgia. No statistically significant relationship was found between WPI score (Figure 1) with BASDAI (p=0.56), ASDAS (p=0.19), BASFI (0.50), RAPID 3 (p=0.70), CRP (p=0.25), and ESR (p=0.30). Also, no statistically significant relationship was found between SS score (Figure 1) with BASDAI (p=0.12), ASDAS (p=0.87), BASFI (0.73), RAPID 3 (p=0.75), CRP (p=0.79), and ESR (p=0.90).
Conclusions Despite high frequency of fibromyalgia prevalence in our patients with AS and active disease, the validated tools of disease and functional activity in AS did not measure fibromyalgia pain and symptoms.
Disclosure of Interest None declared