MO376: Can the Urinary Albumin-Creatinine Ratio Be Calculated Over the Urinary Protein-Creatinine Ratio in Chronic Kidney Disease?
Authors: Özgen Emre , Karali Korkmaz Ceyda , Yılmaz Mürvet , Kural Alev 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Urine albumin-to-creatinine ratio (ACR) and protein-to-creatinine ratio (PCR) are used to measure urine protein. Recent guidelines recommend the use of the ACR, and equations have been developed incorporating ACR to predict risk of kidney failure. Where ACR cannot be measured, whether due to cost issues, laboratory inefficiencies, or other reasons, it is helpful to have a method for estimating ACR from PCR as accurately as possible. In this study, we investigated the usability of the formula developed by Keiichi Sumida et al.[1].

METHOD
The formula for calculating the estimated ACR developed by Keiichi Sumida et al. includes urinary PCR, gender, diabetes, and hypertension variables. Between 2020 and 2021, eGFR, PCR, ACR and creatinine tests were requested from 644 patients who met the requirements for the formula and applied to Bakırköy Dr Sadi Konuk Training and Research Hospital Nephrology outpatient clinic. Estimated ACR value was calculated using the formula over PCR. With PCR and ACR measurement performed on the same day and from the same sample, intra-day and inter-day variation in excretion variability was minimized. eGFR values were evaluated in five subgroups as &gt;90, between 60 and 89, between 30 and 59, 15 and 29 and &lt;15, and the concordance between ACR and estimated ACR was examined for each group. PCR and ACR were analyzed by dye binding and immunoturbidimetric methods., and the relationship between estimated ACR and measured ACR was examined using the logarithmic-exponential function formula. NCSS (Number Cruncher Statistical System) 2007 (Kaysville, Utah, USA) program was used for statistical analysis. Descriptive statistical methods (mean, standard deviation, median, first quartile, third quartile, frequency, percentage, minimum and maximum) were used while evaluating the study data. Kruskal–Wallis test and Dunn–Bonferroni test were used for comparisons between groups of more than two quantitative variables that did not show normal distribution. Spearman correlation analysis was used to evaluate the relationships between quantitative variables. Statistical significance was accepted as P &lt; 0.05.

RESULTS
It was conducted with a total of 644 cases, 49.2% (n = 317) male and 50.8% (n = 327) female. Of the subjects participating in the study, 44.4% had a diagnosis of hypertension and 28.7% had diabetes. PCR measurement values of the cases ranged from 7.5 to 5000 mg/g; the mean measurement value is 1048.29 ± 1166.77 mg/g. ACR measurement values of the subjects participating in the study ranged from 0.64 to 4799 mg/g; mean measurement value is 689.05 ± 891.20 mg/g. The estimated ACR measurement values of the cases ranged from 2 to 2843 mg/g; the mean measurement value is 487.87 ± 620.30 mg/g. When Intraclass Correlation Coefficient (ICC) levels were examined between estimated ACR and ACR measurements, the agreement at the level of 0.846 was found to be excellent (ICC = 0.846; P = 0.001; P &lt; 0.01).
In the groups with eGFR ≥90, 60–89, 30–59, 15–29 and &lt;15; The agreement between estimated ACR and ACR measurements was excellent. (ICC = 0.793, 0.799,0.881,0.849, 0.883 P = 0.001; P &lt; 0.01).

CONCLUSION
Urine ACR is the preferred measure of albuminuria; however, if ACR is not available or cannot be measured, ACR estimated from PCR can be helpful in CKD screening, staging, and prognosis.