The effect of three years of TNF-alpha blocking therapy on markers of bone turnover and their predictive value for treatment discontinuation in patients with ankylosing spondylitis: a prospective longitudinal observational cohort study
Arthritis Research & Therapy, 05/08/2012
Arends S et al. – Three years of tumor necrosis factor–alpha (TNF–alpha) blocking therapy results in a bone turnover balance that favors bone formation; especially mineralization, in combination with continuous improvement of lumbar spine Bone mineral density (BMD). Early change in serum collagen–telopeptide (sCTX) can serve as an objective measure in the evaluation of TNF–alpha blocking therapy in ankylosing spondylitis (AS), in addition to the currently used more subjective measures.
Prospective cohort study of 111 consecutive AS outpatients who started TNF–alpha blocking therapy.
Clinical assessments and BTM were assessed at baseline, 3 and 6 months, as well as 1, 2, and 3 years.
Z–scores of BTM were calculated to correct for age and gender.
Bone mineral density (BMD) was assessed yearly.
After 3 years, 72 patients (65%) were still using their first TNF–alpha blocking agent.
In these patients, TNF–alpha blocking therapy resulted in significantly increased bone–specific alkaline phosphatase, a marker of bone formation; decreased serum collagen–telopeptide (sCTX), a marker of bone resorption; and increased lumbar spine and hip BMD compared to baseline.
Baseline to 3 months decrease in sCTX Z–score (HR: 0.394, 95% CI: 0.263–0.591), AS disease activity score (ASDAS; HR: 0.488, 95% CI: 0.317–0.752), and physician's global disease activity (HR: 0.739, 95% CI: 0.600–0.909) were independent inversely related predictors of time to treatment discontinuation because of inefficacy or intolerance.
Early decrease in sCTX Z–score correlated significantly with good long–term response regarding disease activity, physical function, and quality of life.
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