Association between proteinuria and mineral metabolism disorders in chronic kidney disease: the Japan chronic kidney disease database extension (J-CKD-DB-Ex)

Chronic kidney disease-mineral and bone disorder (CKD-MBD) are recognized as a systemic disease affecting the prognosis of patients with CKD. Proper management of CKD-MBD is important to improve the prognosis of patients with CKD. Although proteinuria is recognized as a poor prognostic factor in these patients, few reports have examined its association with CKD-MBD. We examined the association between proteinuria and CKD-MBD using data from the Japan Chronic Kidney Disease Database Extension (J-CKD-DB-Ex). Among the patients registered in the J-CKD-DB-Ex, 30,977 with CKD stages G2–G5 who had serum creatinine, albumin, calcium, and phosphate concentrations measured at least once and urinalysis performed were included. The patients were divided into four groups (negative, 1+, 2+, and 3+) according to the degree of proteinuria. The association between proteinuria and CKD-MBD was examined by a logistic regression analysis. In a model adjusted for age, sex, diabetes, and the estimated glomerular filtration rate (eGFR), the odds ratio of the 3 + group compared with the negative group significantly increased to 2.67 (95% confidence interval, 2.29–3.13) for hyperphosphatemia, 2.68 (1.94–3.71) for hypocalcemia, and 1.56 (1.24–1.98) for hypomagnesemia. Proteinuria is associated with hyperphosphatemia, hypocalcemia, and hypomagnesemia in patients with CKD independently of eGFR.