New selectivity index calculated using protein fraction as a substitute for the conventional selectivity index.
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.
['Nakamura|Jun|J|', 'Nagatoya|Katsuyuki|K|', 'Fujii|Naohiko|N|', 'Warada|Aki|A|', 'Tokuyama|Atsuyuki|A|', 'Masuyama|Satoshi|S|', 'Kajimoto|Sachio|S|', 'Haga|Ryota|R|', 'Yamauchi|Atsushi|A|']
D000328:Adult D000368:Aged D000419:Albuminuria D001706:Biopsy D015331:Cohort Studies D005260:Female D005938:Glucocorticoids D006801:Humans D053208:Kaplan-Meier Estimate D007668:Kidney D007677:Kidney Function Tests D008297:Male D008875:Middle Aged D008970:Molecular Weight D009404:Nephrotic Syndrome D011237:Predictive Value of Tests D011507:Proteinuria D012016:Reference Values D012189:Retrospective Studies D016896:Treatment Outcome
Transferrin Glucocorticoid Nephrotic syndrome Albumin