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Hypercalciuria: its value as a predictive risk factor for nephrolithiasis in asymptomatic primary
F Saponaro1,2, F Cetani3, L Mazoni3
1Department of Pathology, University of Pisa, Pisa, Italy. federica.saponaro@unipi.it.
Insights
Hypercalciuria predicts kidney stones in patients with asymptomatic primary hyperparathyroidism (aPHPT). However, this urinary calcium excretion has a low positive predictive value for identifying nephrolithiasis.
Area of Science:
- Endocrinology
- Nephrology
- Urology
Background:
- Recent guidelines for asymptomatic primary hyperparathyroidism (aPHPT) include hypercalciuria as a surgical criterion.
- The predictive value of hypercalciuria for nephrolithiasis requires further validation.
Purpose of the Study:
- To determine the prevalence of silent kidney stones in aPHPT patients.
- To assess the sensitivity, specificity, and predictive value of various hypercalciuria cut-offs for detecting nephrolithiasis.
Main Methods:
- 176 patients with aPHPT underwent evaluation of serum and urinary parameters.
- Kidney ultrasound was used to identify silent nephrolithiasis.
Main Results:
- Silent kidney stones were detected in 21.6% of patients.
- Hypercalciuria was a significant predictor of nephrolithiasis across multiple criteria (e.g., >400 mg/24h, >231 mg/24h).
- Despite predictive significance, the positive predictive value of hypercalciuria for nephrolithiasis was low (27.4-32.7%).
Conclusions:
- Hypercalciuria is a validated predictor of nephrolithiasis in aPHPT.
- The low positive predictive value of hypercalciuria limits its utility in routine screening for kidney stones.
Context:
The latest guidelines of the 4th International Workshop on Asymptomatic Primary Hyperparathyroidism (aPHPT) reintroduced hypercalciuria (i.e. urinary calcium > 400 mg/day) as criterion for surgery. However, the value of hypercalciuria as a predictor of nephrolithiasis and the correct cut-off values still need to be confirmed.
Objective:
To evaluate the prevalence of silent kidney stones in a large series of patients with aPHPT and the sensibility, specificity and predictive value of different cut-off values of hypercalciuria in identifying patients with nephrolithiasis.
Design:
One hundred seventy-six consecutive patients with aPHPT were evaluated at our Institution by serum and urinary parameters and kidney ultrasound.
Results:
Silent nephrolithiasis was found in 38 (21.6%) patients. In the univariate and multivariate model, hypercalciuria was a predictor of nephrolithiasis using the criterion of 400 mg/24 h [(OR 2.30, (1.11-4.82) P = 0.025], 4 mg/kg/bw [OR 2.65, (1.14-6.25) P = 0.023], gender criterion [OR 2.79, (1.15-6.79) P = 0.023] and the cut-off value derived from the ROC analysis [(> 231 mg/24 h) OR 5.02 (1.68-14.97) P = 0.004]. Despite these several predictive criteria, however, hypercalciuria had a low positive predictive value (PPV), ranging from 27.4 to 32.7%.
Conclusions:
Hypercalciuria is a predictor of nephrolithiasis, but its PPV is low.
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