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

Abstract

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. 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, alpha(1)-microglobulin, sulphate, oxalate, citrate and fetuin-A (ELISA) were determined. 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 <or=2.1 mg/day. Values of urine fetuin-A did not correlate with gender, age or BMI. 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.