Abstract
Background: Calcium oxalate (CaOx) stone is the most common type of stones formed in the urinary tract. Formation of CaOx stone is driven by increased CaOx crystallization in urine.
Objective: To develop a new test, called indole-reacted calcium oxalate crystallization index (iCOCI), and to measure the capability of urine to produce CaOx crystals.
Methods: One hundred samples of 24-h human urine samples obtained from CaOx stone-forming subjects (SFS, n = 50) and non-stone subjects (NSS, n = 50). The levels of oxalate were determined by two methods, i.e., oxalate oxidase method and iCOCI test. Unpaired student t - test, Pearson’s correlation, and receiver operating characteristic (ROC) analysis were performed.
Results: The urinary oxalate levels in CaOx SFS were significantly higher than those in NSS. Likewise, urinary iCOCI levels in SFS were significantly greater than those in NSS. ROC analysis revealed the area under ROC curves of 0.588 (95% CI: 0.472 - 0.703) and 0.897 (95% CI: 0.838 - 0.956) for urinary oxalate and iCOCI tests, respectively. At the cutoff of 6.2 mg/day, sensitivity and specificity of urinary oxalate test were 60.0% and 58.0%, respectively. The urinary iCOCI test yielded the sensitivity of 88.0% and specificity of 74.0% at the cutoff of 0.8 COM eqv., g/day. Urinary oxalate was positively correlated with urinary iCOCI both in NSS and SFS groups, but it was more pronounced in SFS group.
Conclusion: The urinary oxalate and iCOCI levels in patients with CaOx nephrolithiasis were increased compared to individuals without kidney stones. Diagnostic performance of urinary iCOCI test was remarkedly greater than the urinary oxalate test. Increased urinary oxalate was highly correlated with increased urinary iCOCI. Plausibly, increased urinary oxalate contributed to increased capability of urine to form CaOx crystals.
DOI
10.56808/2673-060X.5438
Recommended Citation
Boonla, Chanchai
(2024)
"Urinary oxalate excretion is increased in calcium oxalate nephrolithiasis patients and associated with increased urinary capacity of calcium oxalate crystallization,"
Chulalongkorn Medical Journal: Vol. 67:
Iss.
1, Article 10.
DOI: https://doi.org/10.56808/2673-060X.5438
Available at:
https://digital.car.chula.ac.th/clmjournal/vol67/iss1/10