Background: Ankylosing spondylitis (AS) is a chronic systemic inflammatory rheumatic
disease that specifically affects the spine and sacroiliac joint. AS diagnosis is often delayed in
the clinical practice and this delay may cause the patients to miss the chance of early treatment. Fibromyalgia
(FM) is a frequently encountered clinical syndrome, fibromyalgianess is a term used
when patients who are diagnosed with inflammatory arthropathies meet the criteria for FM syndrome
as shown in rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjogren syndrome,
Objectives: We aimed primarily to assess the frequency of concomitant diagnosis of FM syndrome
in AS patients and study its impact on clinical disease aspects. Secondary, our aim extended as a
preliminary pilot study to assess the Plasma Pentraxin-3(PTX-3) as a potential marker for the diagnosis
of FM syndrome in AS patients.
Methods: Plasma PTX-3 in 61 AS patients was compared to 60 matched controls. FM was diagnosed
by FM Rapid Screening Tool.
Bath AS disease activity index (BASDAI) and AS disease assessment score using C- reactive protein
(ASDAS-CRP), Bath AS functional impairment index (BASFI), Bath AS metrology index
(BASMI), AS quality of life (ASQoL) scale, Beck Depression Inventory, and Bath AS Radiology
Index (BASRI) were assessed.
Results: The patients were categorized into two groups according to the concomitant diagnosis of
FM syndrome. Group I included 14 (22.9%) AS patients who fulfilled the clinical diagnosis of FM
syndrome. Group II included 47 (77.1%) AS patients without FM syndrome. AS patients with FM
(Group I) had significantly(p<0.001) increased an average of ages, disease duration, diagnostic delay
of AS, switching of bDMARDs, morning stiffness duration, ASDAS-CRP, BASFI, ASQoL
score, BASDAI (p=0.008), and BDI score (p=0.005) compared to AS patients without FM (Group
II). PTX-3 levels were significantly (p<0.001) higher in Group I (p<0.001) (median, 0.23; IQR,
0.15-0.41 ng/ml) than Group II (median, 0.13; IQR, 0.035-0.21ng/ml) which showed no significant
differences (p>0.05) compared to the controls. PTX-3 levels had significant positive correlations
(p<0.05) with disease duration, BASFI, and ASQOl. Age, female sex, switch of biologic, ASDAS -
CRP, and PTX-3 were significant predictors of FM in AS patients.
Conclusion: These results indicate that concomitant FM is a significant problem in patients with
AS and its presence is associated with higher disease activity, impaired function as well as an overall
negative impact on QoL. Easy scanning of suspicious cases of FM with FiRST questionnaire
can be done in daily practice. PTX-3 is more or less accurate as the clinical features to improve the
diagnostic certainty of FM in the presence of AS with a proven sensitivity of 62.3%, a specificity
of 90%, a positive predictive value of 82.75%, and a negative predictive value of 73.9%.