Jun Nakamura1,2, Katsuyuki Nagatoya3, Naohiko Fujii4, Aki Warada1, Atsuyuki Tokuyama1, Satoshi Masuyama1, Sachio Kajimoto1,2, Ryota Haga1, Atsushi Yamauchi1. 1. Department of Nephrology, Osaka Rosai Hospital, Nagasone-cho, Kita-ku, Sakai, 1179-3, Osaka, Japan. 2. Department of Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan. 3. Department of Nephrology, Osaka Rosai Hospital, Nagasone-cho, Kita-ku, Sakai, 1179-3, Osaka, Japan. katsuyuki@osakah.johas.go.jp. 4. Department of Nephrology, Hyogo Prefectural Nishinomiya Hospital, Nishinomiya, Hyogo, Japan.
Abstract
BACKGROUND: Selectivity index (SI) of proteinuria, calculated using the clearance ratio of immunoglobulin G to transferrin, predicts the response to glucocorticoids in patients with nephrotic syndrome. However, there is disagreement regarding the suitability of SI. Therefore, alternate indices should be considered. This study investigated whether or not selectivity index protein fraction (SIPF) was inferior to SI for the prediction of the response to glucocorticoids. METHODS: Forty-nine patients with nephrotic syndrome were evaluated. On the basis of molecular weight and protein fraction, as an inexpensive substitute for SI, the clearance ratio of the albumin to γ fractions measured in serum and urine protein fractions was defined as SIPF. The quality of SIPF was examined. Moreover, the best cutoff value of SIPF was determined; and SIPF distribution, according to histopathological diagnosis by renal biopsy, was examined. RESULTS: SIPF was strongly correlated with SI (r = 0.79, P < 0.001). The area under the receiver operating characteristic (ROC) curve of SIPF and SI was not significantly different (P = 0.18). The best cutoff value of SIPF was 0.45. In the group with SIPF > 0.45, only two patients with minimal change disease (MCD) achieved complete remission. In the group with SIPF ≤ 0.45, all patients with MCD achieved complete remission, although eight patients with other histopathological diagnoses did not achieve complete remission. CONCLUSIONS: Analysis of protein fractions as a substitute for SI may be useful for predicting response to glucocorticoids in patients with nephrotic syndrome.
BACKGROUND: Selectivity index (SI) of proteinuria, calculated using the clearance ratio of immunoglobulin G to transferrin, predicts the response to glucocorticoids in patients with nephrotic syndrome. However, there is disagreement regarding the suitability of SI. Therefore, alternate indices should be considered. This study investigated whether or not selectivity index protein fraction (SIPF) was inferior to SI for the prediction of the response to glucocorticoids. METHODS: Forty-nine patients with nephrotic syndrome were evaluated. On the basis of molecular weight and protein fraction, as an inexpensive substitute for SI, the clearance ratio of the albumin to γ fractions measured in serum and urine protein fractions was defined as SIPF. The quality of SIPF was examined. Moreover, the best cutoff value of SIPF was determined; and SIPF distribution, according to histopathological diagnosis by renal biopsy, was examined. RESULTS: SIPF was strongly correlated with SI (r = 0.79, P < 0.001). The area under the receiver operating characteristic (ROC) curve of SIPF and SI was not significantly different (P = 0.18). The best cutoff value of SIPF was 0.45. In the group with SIPF > 0.45, only two patients with minimal change disease (MCD) achieved complete remission. In the group with SIPF ≤ 0.45, all patients with MCD achieved complete remission, although eight patients with other histopathological diagnoses did not achieve complete remission. CONCLUSIONS: Analysis of protein fractions as a substitute for SI may be useful for predicting response to glucocorticoids in patients with nephrotic syndrome.