Tracking Cartilage Turnover: Urinary CTX-II as a Biomarker for Early Rheumatoid Arthritis Progression and Anti-TNF Therapy Response

Authors : Bora Uzuner, Sertaç Ketenci, Ayhan Bilgici, Ender Salbaş, Abdülkerim Bedir

Pages : 173-184

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Publication Date : 2025-07-28

Article Type : Research Paper

Abstract :Introduction: This study aimed to evaluate urinary C-telopeptide of type II collagen (CTX-II) as a biomarker of cartilage turnover, disease activity, and anti-TNF therapy response in rheumatoid arthritis (RA), with a focus on early disease. Methods: In a prospective cohort study (June–October 2010), 39 RA patients initiating anti-TNF therapy (adalimumab, etanercept, or infliximab) and 36 age- and sex-matched healthy controls were enrolled. Baseline and 3-month assessments included urinary CTX-II (corrected for creatinine), Disease Activity Score in 28 joints (DAS28), Health Assessment Questionnaire (HAQ), and van der Heijde modified Total Sharp Score (mTSS). Correlations between CTX-II and disease activity or radiographic damage were analyzed using Spearman’s rank correlation. Changes in CTX-II were assessed with the Wilcoxon signed-rank test, and subgroup analyses compared early (<3 years) versus established RA. Results: At baseline, RA patients had significantly higher urinary CTX-II levels than controls (447.8 ± 359.3 vs. 233.8 ± 122.4 ng/mmol, p<0.005). CTX-II correlated positively with DAS28 (ρ=0.609, p<0.001), HAQ (ρ=0.493, p=0.001), and joint counts, and was twofold higher in RF-positive patients (557.0 ± 395.0 vs. 252.8 ± 159.6 ng/mmol, p=0.018). After 3 months, early RA patients (n=11) showed a significant 45% reduction in CTX-II (p=0.016), while established RA patients (n=20) showed no change (p=0.421). Patients in remission (DAS28 <2.6, n=12) had CTX-II levels comparable to controls (p=0.005). High baseline CTX-II (≥479 ng/mmol, n=8) predicted a 46% reduction post-therapy (p=0.017). Conclusion: Urinary CTX-II is a dynamic biomarker of cartilage turnover and anti-TNF response, particularly in early RA. Its association with RF positivity and remission suggests a role in personalized RA management. Larger studies are needed to validate standardized cut-offs for clinical use.
Keywords : idrar CTX-II, anti-TNF tedavi, kıkırdak turnover, erken RA, BİYOBELİRTEÇ, ROMATOİD ARTRİT

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