Estimation of 24 hour urine protein excretion using urine creatinine/albumin ratio

Abstract

BackgroundThere is still a lack of quantitative description of the relationship between urine creatinine/albumin ratio (ACR) and 24 hour urine protein excretion (24 h UPE). We aimed to study the correlation between 24 h UPE and urine ACR and develop a prediction model for 24 h UPE.Methods This was a retrospectively observational study. All individuals with paired urine ACR and 24 h UPE tested on the same day in Sichuan Provincial People’s Hospital during September 1st, 2018 to December 31st, 2019 were enrolled. Correlation and agreement between urine ACR and 24 h UPE were evaluated. A prediction model of 24 h UPE was further developed and validated.Results 671 subjects were identified. Urine ACR had a good correlation with 24 h UPE in general population (Spearman’s coefficient = 0.939; p < 0.001) but the agreement between these two measurements was not consistently good (overall ICC = 0.870; 95% CI: 0.849–0.888; p < 0.001). Our multivariable transform model of 24 h UPE had good performance (R2 = 0.829) and validated high accuracy (RMSE = 0.0227, rRSME = 3.1%).Conclusions Urine ACR has a good correlation with 24 h UPE in general population but is not a reliable surrogate for 24 h UPE. Our prediction model is a useful tool for estimating 24 h UPE, however, 24 h UPE is still mandatory in situations when accurate quantification of proteinuria is required.Key messages:1. urine ACR has a good correlation with 24h UPE but is not a reliable surrogate for 24h UPE.2. Our prediction model is helpful to estimate 24h UPE, with good performance (R2=0.829) and validated high accuracy (RMSE=0.0227, rRSME=3.1%); however, 24h UPE is still mandatory in situations when accurate quantification of proteinuria is required.