Comparative evaluation of dual-energy X-ray absorptiometry (DEXA) and biochemical bone markers (P1NP, and Vitamin D3)

Background: Dual-energy X-ray absorptiometry (DEXA) remains the gold standard for evaluating bone mineral density (BMD), but its limitations in accessibility and cost have driven interest in biochemical markers like procollagen type I N-terminal propeptide (P1NP) and vitamin D3. This study aimed to assess the diagnostic alignment and predictive value of P1NP and vitamin D3 in relation to DEXA-based bone density classifications. Methods: A cross-sectional comparative study was conducted on 150 adults in Basrah, Iraq, equally divided into three groups based on DEXA-derived T-scores: normal, osteopenia, and osteoporosis. Serum P1NP and vitamin D3 levels were measured using automated chemiluminescent immunoassays. Non-parametric statistical tests were used due to the skewed distribution of data. Kruskal-Wallis tests compared marker levels across groups, while Spearman’s correlation assessed relationships with T- and Z-scores. Multiple linear regression evaluated their predictive capacity, and ROC analysis determined diagnostic accuracy. Results: P1NP levels increased progressively across normal, osteopenic, and osteoporotic groups, with a statistically significant difference (p = 0.048). Vitamin D3 levels were lower in the osteoporosis group but did not significantly differ across all categories (p = 0.106). Correlation analysis revealed no significant relationship between P1NP and T- or Z-scores. Vitamin D3 showed a weak but significant positive correlation with T-score (r = 0.180, p = 0.027). In regression analysis, vitamin D3 significantly predicted T-scores (p = 0.002) but not Z-scores. ROC analysis showed poor discriminative ability for both markers, with AUCs ranging from 0.401 to 0.588. Conclusion: While vitamin D3 demonstrated a modest correlation and predictive value for T-scores, neither P1NP nor vitamin D3 showed sufficient diagnostic power to substitute for DEXA. Their utility may lie in complementary roles, particularly in settings where imaging access is limited. Integration with imaging, rather than replacement, is recommended.