Converting PCR to ACR to Develop CKD Risk Equations

Washington, DC—Staging of chronic kidney disease (CKD) commonly relies on the urine albumin-creatinine ratio (ACR), used in equations to predict the risk of adverse clinical outcomes. However, according to Keiichi Sumida, MD, MPH, PhD, FASN, and colleagues, many trial cohorts and health systems prefer to measure urine protein-creatinine ratio (PCR) rather than ACR. Because those assays measure different components of protein, there are few available data on how levels of PCR may be converted to ACR.

To develop an equation for conversion of PCR to ACR, Dr. Sumida et al. conducted analyses of data from cohorts in the CKD Prognosis Consortium on patients with measurements of PCR and ACR performed <90 days apart. To account for multiple records per person, analyses were performed using all available data within individual cohorts. The researchers then conducted a meta-analysis to model log-PCR using random effects and linear splines. Results were reported during a poster session at Kidney Week 2019 in a poster titled Conversion of Urine Protein-Creatinine to Albumin-Creatinine Ratio for Use in CKD Risk Equations.

In all, there were 11 cohorts: two general population, three high cardiovascular risk, and six CKD cohorts representing 34,708 participants from North America, Europe, and Japan. Average age was 58 years, 50% were female, and 7.4% were black. Median ACR was 181 mg/g and median PCR was 373 mg/g.

Because there was no relationship between ACR and PCR at <50 mg/g, those values were excluded in the equation development. Above PCR 50 mg/g, there was a log-linear relationship with a slightly shallower slope at PCR >500 mg/g (P<.001). Relationships between PCR and ACR were similar across cohorts, and demographics, hypertension, cardiovascular disease, and diabetes status.

“Guidelines recommend measurement of ACR. However, when ACR is not available, we developed an equation to convert PCR levels >50 mg/g to ACR for use in risk equations. Lower levels of PCR were not amenable to harmonization,” the researchers said.

Source: Sumida K, Nadkami GN, Polkinghome K, L Heerspink, HJ. Conversion of urine protein-creatinine to albumin-creatinine ratio for used in CKD risk equations.” Abstract of a poster presented at the American Society of Nephrology Kidney Week 2019 (Abstract TH-PO392), November 7, 2019, Washington, DC.