Vitamin D status in ankylosing spondylitis patients: Relation to bone health, disease activity, functional status, spine mobility and enthesitis

Aim of the work: To evaluate serum levels of vitamin D in ankylosing spondylitis (AS) patients in relation to bone mineral density, bone metabolism, and disease activity, functional status, spine mobility and extent of enthesitis. Patients and methods: Sixty AS patients and 60 controls were included. Bath AS disease activity index (BASDAI), functional index (BASFI), metrology index (BASMI), AS disease activity score (ASDAS), and Maastricht AS enthesitis score (MASES) were assessed. Serum levels of vitamin D3, carboxy-terminal telopeptide of type-I collagen (CTX-1), alkaline phosphatase (ALP) and bone alkaline phosphatase (bALP) were measured. Dual-energy X-ray absorptiometry (DXA) was assessed. Results: Patients mean age was 31.7 +/- 9.1 years, disease duration 7.8 +/- 4.4 years and were 46 males and 14 females. The mean BASDAI was 3.9 +/- 1.02, ASDAS 2.7 +/- 0.98, BASFI 3.6 +/- 2.1, BASMI 4.5 +/- 1.6 and MASES 4.4 +/- 3.2. Patients had significantly (p = 0.001) lower levels of vitamin D (13 +/- 7.8 vs 29.9 +/- 9.5 ng/mL) and higher CTX-1 (547.5 +/- 130.1 vs 230.1 +/- 34.9 pg/mL), ALP (195.8 +/- 100.8 vs 120.8 +/- 10 IU/L) and bALP (48.4 +/- 7.3 vs 21.03 +/- 3.2 IU/L) compared to controls. Vitamin D significantly correlated with BMD (p = 0.04), inversely with CTX-1 (r = -0.22,p < 0.001), ALP (r = -0.03,p = 0.005), bALP (r = -0.22,p = 0.049), BASDAI (r = -0.57,p < 0.001), ASDAS (r =-0.37,p = 0.04), BASMI (r = -0.18,p = 0.03), MASES (r = -0.03,p = 0.008) and sacroiliitis grading (r = -2.4,p < 0.001). Vitamin D deficiency was associated with peripheral joints affection, enthesitis and not receiving sulfasalazine. Conclusion: Serum vitamin D levels were decreased in patients with AS and were more deficient in relation to disease activity and bone turnover. Vitamin D may play a role in the pathogenesis and progression of AS in Egyptian patients which should be more comprehensively investigated. (C) 2020 Egyptian Society of Rheumatic Diseases. Publishing services provided by Elsevier B.V.