Serum TRACP-5b as a stable marker of bone resorption in Primary and Rheumatoid Arthritis -related Osteoporosis : clinical correlates and diagnostic utility

Abstract

Background
Osteoporosis (OP) is a systemic bone condition, characterized by low bone mass and disturbed microarchitecture, that raises fracture risk susceptibility and lowers the quality of life. Tartrate-resistant acid phosphatase isoform 5b (TRACP-5b) is a biomarker that tracks the progression of bone resorption and monitors treatment effectiveness. Therefore, this work intended to assess TRACP-5b levels in two types of osteoporosis, postmenopausal primary OP and Rheumatoid Arthritis (RA)-related secondary OP, and to evaluate its potential as an alternative to bone mineral density (BMD) measurement when Dual-energy X-ray absorptiometry (DEXA) is unavailable.


Methods
A hospital-based single-center cross-sectional observational study, where demographic data, therapeutic history, Disease activity score 28 (DAS28), DEXA, Fracture risk assessment tool (FRAX), and TRACP-5b levels were evaluated in both types of OP (and the normal population as reference). Detection of relation and correlation between different parameters was calculated, and the ROC curve analysis was used to test the diagnostic performance of TRACP-5b.


Results

No differences between the two OP groups regarding TRACP-5b, BMD & FRAX. TRACP-5b levels were significantly higher in the 1ry OP (all newly diagnosed & untreated) group (Median 5.5 ng/mL). Most of the RA patients (85.7%) had moderate to severe DAS28 and positively correlated with TRACP-5b level (
r
 = 0.513). The ROC curve at a cut-off of 3.1 ng/mL, AUC of 0.740 (
p
 = 0.002), delivered a better diagnostic accuracy to differentiate the 1ry OP & the control group.



Conclusion
This study substantiated that TRACP-5b is a relatively sensitive indicator for osteoclast activity and offers likely advantages in early tracking of the process of bone resorption and treatment response indicator before its detection by DEXA.