Spot urine protein/creatinine ratio as a reliable estimate of 24-hour proteinuria in patients with immunoglobulin A nephropathy, but not membranous nephropathy

Seiji Kobayashi,Hiroyuki Terawaki,Takashi Yokoo,Hoichi Amano,Yoshindo Kawaguchi,Makoto Ogura

doi:10.1186/s12882-019-1486-8

Abstract

BackgroundProteinuria is known to be associated with both kidney function deterioration and cardiovascular diseases. While proteinuria estimation from 24-h urine samples has traditionally been considered as the standard method for assessment of the degree of urinary protein excretion, sample collection is associated with several technical problems such as inaccurate collection and the potential spread of drug-resistant pathogens. Therefore, the spot urine protein/creatinine ratio (PCR) assessment is currently recommended as an alternative. While the utility of PCR has been validated, studies on the association between spot urine PCR and 24-h proteinuria (24HP) in patients with chronic glomerular nephritis (CGN) and nephrotic syndrome (NS) are limited. This study aimed to evaluate whether an estimated result from a spot urine PCR could sufficiently approximate the daily urine protein excretion amount from a 24-h urine sample in patients with immunoglobulin A nephropathy (IgAN), minimal change disease (MCD), and membranous nephropathy– nephrotic syndrome (MN-NS).MethodsThe study participants included 161 patients with IgAN, MCD, or MGN-NS at the Jikei University Kashiwa Hospital and Kanagawa Prefecture Shiomidai Hospital. The correlation between spot urine PCR and a 24-h urine protein was investigated using linear regression analysis with Spearman’s correlation (r) coefficient and intraclass correlation coefficient (ICC).ResultsWhile high correlation coefficients (r = 0.86, P < 0.001) and substantial agreement (ICC: 0.806, P < 0.001) were observed in patients with IgAN, similar correlations were not observed in patients with MCD or MN-NS. In the patients with MCD, r was 0.53 (P < 0.001), which signified a slight correlation, and in the patients with MN-NS, r was 0.289 (P = 0.17), which was not statistically significant.ConclusionsThis study revealed that spot urine PCR is a reliable estimate of 24HP value in patients with IgAN. In contrast, there is a considerable difference between the daily urine protein excretion amount based on a 24-h urine sample and that which is calculated from spot urine PCR in patients with NS.

Highlights

Proteinuria is known to be associated with both kidney function deterioration and cardiovascular diseases
This study aimed to evaluate the correlation and agreement between spot urine protein/creatinine ratio (PCR) with urine protein excretion measured by 24 h urinary collection in patients with chronic glomerular nephritis (CGN) and nephrotic syndrome (NS)
Patient population The study participants included 161 patients with immunoglobulin A nephropathy (IgAN), minimal change disease (MCD), or membranous nephropathy –nephrotic syndrome (MN-NS) and who were diagnosed through kidney biopsy at the Jikei University Kashiwa Hospital and Kanagawa Prefecture Shiomidai Hospital between 2008 and 2015

Summary

Introduction

Proteinuria is known to be associated with both kidney function deterioration and cardiovascular diseases. While proteinuria estimation from 24-h urine samples has traditionally been considered as the standard method for assessment of the degree of urinary protein excretion, sample collection is associated with several technical problems such as inaccurate collection and the potential spread of drug-resistant pathogens. This study aimed to evaluate whether an estimated result from a spot urine PCR could sufficiently approximate the daily urine protein excretion amount from a 24-h urine sample in patients with immunoglobulin A nephropathy (IgAN), minimal change disease (MCD), and membranous nephropathy– nephrotic syndrome (MN-NS). The standard method to assess proteinuria is the protein content of an accurately collected 24-h urine sample [6]. Collection of 24-h urine in the hospital can cause spread of some species of bacteria, such as multidrug-resistant Pseudomonas aeruginosa, which causes urinary tract infection [8, 9]

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