Comparison of Measured Urine Albumin-to-Creatinine Ratio (mUACR) with Derived UACR (dUACR)

Background: Proteinuria is a key marker for kidney disease, but albuminuria provides better risk prediction, especially in diabetics. UACR is preferred over UPCR due to higher sensitivity at low protein levels. Older studies often report only UPCR, limiting the use of albumin-specific data. Equations have been developed to estimate UACR from UPCR for better data utilization. We compared measured and derived UACR values to assess the accuracy of these equations across eGFR levels. Methods: This prospective observational cross-sectional study measured both UPCR and UACR [m(UACR)] from the same spot urine sample. Derived UACR [d(UACR)] was calculated using equations by Weaver et al. and compared with mUACR. The study assessed whether these equations remain accurate across different levels of eGFR. Results: 1)Correlation coefficient between [m(UACR)] and [d(UACR)] was 0.9 in the study population. [correlation coefficient r = 0.9] (p = 0.001)] 2)Correlation coefficient between [m(UACR)] and median [d(UACR)] was 0.9 in all stages of CKD as per eGFR levels with maximum correlation found to be in stage 5 CKD with eGFR below 15ml/min. [correlation coefficient r =0.974 (p = 0.001)] Conclusion: This prospective study validated equations for converting UPCR to UACR, showing strong correlation, especially in proteinuria stage A2 and above. [d(UACR)] can be a useful substitute when [m(UACR)] is unavailable, aiding CKD research, screening, and risk prediction efforts. A key strength was the use of the same urine sample for both UPCR and UACR, minimizing variability due to intra-individual fluctuations, which has not been done in other studies.It is also the first study to compare derived and measured UACR in the Indian population, filling a gap in existing research.Spearman's correlation between m(UACR) and d(UACR)