Serum osteopontin as a laboratory biomarker in urolithiasis: Correlation with renal biochemical and hydration markers
Reeta Rajagambeeram, Vickneshwaran Vinayagam, Ranjani RajendiranObjectives:
The objective of the study is to evaluate serum osteopontin (OPN) levels and their association with biochemical markers of renal function and hydration status in patients with urolithiasis.
Materials and Methods:
This case-control study included 87 participants (44 urolithiasis patients and 43 age- and sex-matched healthy controls). Biochemical parameters, including serum urea, creatinine, calcium, phosphorus, uric acid, and OPN, were measured. Urine pH and urine specific gravity (USG) were assessed. Calcium-phosphorus (Ca:P) product, Ca:P ratio, and urine total dissolved solids (U-TDS) were also calculated.
Statistical analysis:
Variables were compared between groups using Student’s t -test or Wilcoxon rank-sum test, with receiver operating characteristic (ROC) analysis performed to determine diagnostic accuracy. p < 0.05 was considered statistically significant.
Results:
Serum calcium (9.15 ± 1.17 mg/dL) and uric acid (5.04 ± 1.16 mg/dL) were significantly elevated in patients compared to controls, while serum urea (20.97 ± 5.63 mg/dL) and phosphorus (2.91 ± 0.73 mg/dL) were significantly reduced ( p <0.05). Median serum OPN was significantly higher in the urolithiasis group (752.20 ng/ mL) compared to controls (153.5 ng/mL). OPN showed significant positive correlations with urine pH, USG, and U-TDS ( p <0.005). ROC analysis for the total group identified an optimal OPN cut-off of 652 ng/mL (area under the curve [AUC]: 0.800), whereas the female subgroup showed a lower cut-off of 335 ng/mL with improved diagnostic accuracy (AUC: 0.889; 80% sensitivity and specificity).
Conclusions:
Serum OPN levels are significantly elevated in patients with urolithiasis and are associated with urinary markers of hydration status and renal biochemical alterations. The observed sex-specific differences in serum phosphorus levels may contribute to the increased susceptibility to urolithiasis among female patients. Serum OPN may serve as a useful adjunct laboratory biomarker in the evaluation of urolithiasis.