Kidney Week

Abstract: FR-PO0261

Clinical Relevance of C-Terminal Telopeptide of Type I Collagen (CTX) in Assessing Bone Health in CKD-Associated Osteoporosis

Session Information

• Bone and Mineral Metabolism: Clinical Epidemiology and Outcomes
  November 07, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Bone and Mineral Metabolism

• 502 Bone and Mineral Metabolism: Clinical

Authors

• Mainardes, Lorena Catelan, Universidade de Sao Paulo, São Paulo, SP, Brazil

Lorena Catelan Mainardes, MD

• Via Reque Cortes, Daniela del Pilar, Universidade de Sao Paulo, São Paulo, SP, Brazil

Daniela del Pilar Via Reque Cortes, MD

• Lima, Carolina Marquez, Universidade de Sao Paulo, São Paulo, SP, Brazil

Carolina Marquez Lima, MD

• Wagner, Carolina Steller, Universidade de Sao Paulo, São Paulo, SP, Brazil

Carolina Steller Wagner, PhD

• Jorgetti, Vanda, Universidade de Sao Paulo, São Paulo, SP, Brazil

Vanda Jorgetti, MD, PhD

• Carvalho, Aluizio B., Universidade Federal de Sao Paulo, São Paulo, SP, Brazil

Aluizio B. Carvalho, MD, PhD

• dos Reis, Luciene, Universidade de Sao Paulo, São Paulo, SP, Brazil

Luciene dos Reis, PhD

• Canziani, Maria Eugênia, Universidade Federal de Sao Paulo, São Paulo, SP, Brazil

Maria Eugênia Canziani

• Custodio, Melani, Universidade de Sao Paulo, São Paulo, SP, Brazil

Melani Custodio, PhD

• Elias, Rosilene M., Universidade de Sao Paulo, São Paulo, SP, Brazil

Rosilene M. Elias, MD, PhD

• Moyses, Rosa M.A., Universidade de Sao Paulo, São Paulo, SP, Brazil

Rosa M.A. Moyses, MD, PhD

Group or Team Name

• OSTEO4CKD Team.

Background

CKD-associated osteoporosis (CKD-OP) affects bone strength, increasing fracture risk. Current guidelines recommend assessing parathyroid hormone (PTH) levels alongside bone turnover markers. We evaluated the usefulness of C-terminal telopeptide of type I collagen (CTX) in patients with CKD stages 2–5D, comparing with tartrate-resistant acid phosphatase 5 (TRAP5b), a kidney-independent bone resorption marker with limited commercial availability.

Methods

Data from 147 participants in the OSTEO4CKD study and 18 additional patients with CKD5D were analyzed. Serum levels CTX and TRAP5b levels were measured and compared with bone mineral density (BMD) at the lumbar spine (LS), total hip (TH), and femoral neck (FN) using dual-energy X-ray absorptiometry (DXA). Low BMD was defined as T-score < –1.

Results

In the cohort (N = 165), median levels of CTX, TRAP5b, and PTH were 0.64 ng/mL, 4.19 U/L, and 123 pg/mL, respectively, with levels increasing progressively across more advanced stages of CKD. Low BMD at any site was present in 95 patients (57.6%), with prevalence increasing across CKD stages: 33.3% (CKD2), 39.1% (CKD3A), 51.3% (CKD3B), 68.9% (CKD4), and 88.9% (CKD5D). At the FN, low BMD was found in 86 patients (52.1%), ranging from 12.5% in CKD2 to 72.2% in CKD5D. CTX strongly correlated with TRAP5b (r = 0.71, p < 0.0001), and both were associated with PTH (CTX: r = 0.61; TRAP5b: r = 0.48; both p < 0.0001). Among those with elevated CTX (n = 61), 59 had low BMD; among those with elevated TRAP5b (n = 42), 38 had low BMD. In multiple multivariate analyses evaluating factors associated with low BMD at any site—including comparisons between CTX and TRAP5b—elevated CTX and age consistently demonstrated the strongest associations, yielding the highest explanatory power (R² = 0.558). All models were adjusted for sex, eGFR, PTH, and alkaline phosphatase.

Conclusion

These findings support the use of CTX as a surrogate bone resorption marker when TRAP5b is unavailable. Combined assessment of CTX, PTH, and a bone formation marker may enhance the evaluation and management of CKD-OP.

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025qps5fbaa