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. 2023 Apr-Jun;45(2):252-256.
doi: 10.1590/2175-8239-JBN-2022-0079en.

Albumin-to-protein ratio in spot urine samples for analysis of proteinuria selectivity in chronic kidney disease

[Article in English, Portuguese]
Miguel Augusto Martins Pereira  1 , Roger Freitas Ramirez Jordan  1 , Jorge Paulo Strogoff de Matos  2 , José Carlos Carraro-Eduardo  2
Affiliations

Albumin-to-protein ratio in spot urine samples for analysis of proteinuria selectivity in chronic kidney disease

[Article in English, Portuguese]
Miguel Augusto Martins Pereira et al. J Bras Nefrol. 2023 Apr-Jun.

Abstract
in English, Portuguese

Introduction: The albumin-to-creatinine ratio and total protein-to-creatinine ratio in spot urine samples have already been validated as surrogates for 24-hour albuminuria and proteinuria measurements. Thus, we hypothesized that the type of proteinuria, detected by the electrophoretic pattern of 24-hour urine, could be predicted by the simple proportion of albumin in the total urine protein content, using the albumin-to-protein ratio (APR). Our study sought to validate the use of APR as a cheaper substitute for urinary protein electrophoresis (UPE).

Methods: Using different mathematical models, we compared, the albumin fraction in 24-hour urine samples by electrophoresis and the APR ratio in spot samples from 42 outpatients with chronic kidney disease (CKD).

Results: A strong log-order correlation r = 0.84 (0.75-0.92; 95% CI, p = 0.001) was observed between APR and the albumin fraction in the UPE.

Conclusion: The APR can substitute electrophoresis in CKD outpatients.

Introdução:: A utilização da razão albumina/creatinina e da razão proteína total/creatinina em amostras isoladas de urina já foram validadas como substitutos para a albuminúria e proteinúria em 24 horas. Assim, nossa hipótese é que o tipo de proteinúria, dado pelo padrão eletroforético da urina de 24 horas, poderia ser previsto pela simples proporção de albumina no conteúdo total de proteínas na urina, utilizando a razão albumina/proteína (RAP). O presente estudo procurou validar o uso da RAP como um substituto mais prático e de menor custo da eletroforese de proteínas urinárias (EPU).

Métodos:: Foram utilizados diferentes modelos matemáticos a fim de comparar a fração de albumina pela eletroforese em amostras de urina de 24 horas e a RAP em amostras isoladas em 42 pacientes ambulatoriais com doença renal crônica.

Resultados:: Foi observada uma forte correlação logarítmica r = 0,84 (0,75–0,92; 95% CI, p = 0,001) entre a RAP e a fração de albumina pela EPU.

Conclusão:: A RAP pode substituir a eletroforese urinária em pacientes renais crônicos ambulatoriais.

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Conflict of interest statement

Conflict of Interest

All authors declare no conflicts of interest.

Figures

Figure 1
Figure 1. (A) The blue line indicates the simple linear regression obtained using the partial least squares method. The shaded region represents the 95% confidence interval of the regression. (B) Linear regression between the residual obtained from the regression between the APR and the UPE and with the UPE itself. This graph shows a certain degree of dependence between the error and the percentage obtained from electrophoresis. (C) Logarithmic regression between albumin fraction using urinary protein electrophoresis and the APR. UPE = Urinary protein electrophoresis; APR = albumin/protein ratio or index.
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