Abstract: Objective To explore if we can replace 24 hour urine calcium (24 hUCa) with fasting 1 hour urinary calcium (1 hUCa)concentration in diabetes mellitus patients. We explored the factors affecting 24 hUCa,and built the regression equation. Further we judged the agreement of fasting 1 hUCa concentration and 24 hUCa. Finally,we tried to find the best cut-off for fasting 1-hour urinary calcium concentration.Methods Sixty-one diabetes mellitus patients in the endocrine ward of Beijing Chaoyang Hospital, Capital Medical University were invited to attend this test.We collectd the 24 hour urine samples and the following 1 hour urine samples (fasting condition in 6 to 7 o'clock), we detected 24 hUCa, 1 hUCa, measured 24 hour urine output,detected 25-OH-vitamin D and parathyroid hormone (PTH). We did multiple regression analysis to find the factors affecting 24 hUCa,and built the regression equation. More,we judged agreement of fasting 1 hour urinary calcium concentration and 24 hUCa with Bland-Altman analysis. Finally, we made 24 hUCa >350 mg/d the cut point, and used 1 hUCa to draw receiver operating characteristic (ROC) curve, evaluated the sensitivity, the specificity, the misdiagnosis rate.Then we made the chi-square test of paired data.Results Fasting 1 hUCa concentration was the factor affecting 24 hUCa. We could build the regression equation.The agreement of fasting 1 hUCa and 24 hUCa was good. When we diagnosed hypercalciuria with 1 hUCa, choosing 24 hUCa>350 mg/d as the cut point to draw ROC curve,the area under the curve is 0.925. When 1 hUCa was 171.4 mg/L (4.285 mmol/L), it had the sensitivity of 100%、the specificity of 84.9% and the misdiagnosis rate of 50%. When we diagnosed hypercalciuria with 1 hUCa,8 true positives were found,but 8 false positives were diagnosed too. Kappa's coefficient was 0.596, that meant the agreement was ordinary.And we used McNemar method,the difference was statistically significant.Conclusion In diabetes mellitus patients,because of the high misdiagnosis rate, fasting 1 hour urinary calcium concentration can not be used to diagnose hypercalciuria. But,the sensitivity is good,thus it can be used as the primary screening test.When the result of 1 hUCa detection is positive,we should measure 24 hUCa again.

Key words: hypercalciuria, diagnosis, fasting 1 hour urinary calcium concentration