Urine fetuin‐A values in relation to the presence of urolithiasis

OBJECTIVE To investigate the relationship of urine fetuin‐A and other promotors and inhibitors of urine crystalization with urolithiasis, as fetuin‐A inhibits the precipitation of hydroxyapatite from supersaturated solutions of calcium and phosphate in vitro but no information on urine fetuin‐A in patients with urolithiasis is available. PATIENTS AND METHODS In all, 39 patients with urolithiasis and 22 individuals with no urolithiasis or probands with undetected stones were involved. All patients underwent kidney ultrasonography and X‐ray examination, and body mass index (BMI) was calculated. Serum creatinine, parathyroid hormone, calcium, magnesium, anorganic phosphate, uric acid and urine creatinine, albumin, α 1 ‐microglobulin, sulphate, oxalate, citrate and fetuin‐A (ELISA) were determined. RESULTS The patients with urolithiasis had lower urine fetuin‐A levels (median 4.9 vs 0.77 mg/day; P  < 0.01) and citraturia levels (1.7 vs 5.1 mmol/day; P  = 0.02); and higher calciuria (6.5 vs 5.2 mmol/day) and oxaluria (0.47 vs 0.25; P  = 0.04). Patients with fetuin‐A levels in the lowest quartile had an odds ratio of 36 compared with individuals in the highest quartile. The sensitivity of the urine fetuin‐A level for urolithiasis was 97.4% and specificity was 100% (area under the curve 0.99; 95% confidence interval 0.94–1.0) using a urine fetuin‐A threshold of ≤2.1 mg/day. Values of urine fetuin‐A did not correlate with gender, age or BMI. CONCLUSIONS Our study indicates, for the first time, that patients with documented urolithiasis had lower fetuin‐A concentrations independent of other conventional promotors and inhibitors of urine crystallization.