Conversion of Urine Protein–Creatinine Ratio or Urine Dipstick Protein to Urine Albumin–Creatinine Ratio for Use in Chronic Kidney Disease Screening and Prognosis

Abstract

; for the Chronic Kidney Disease Prognosis Consortium ‡ Background: Although measuring albuminuria is the preferred method for defining and staging chronic kidney disease (CKD), total urine protein or dipstick protein is often measured instead. Objective: To develop equations for converting urine proteincreatinine ratio (PCR) and dipstick protein to urine albumincreatinine ratio (ACR) and to test their diagnostic accuracy in CKD screening and staging. Design: Individual participant-based meta-analysis. Setting: 12 research and 21 clinical cohorts. Participants: 919 383 adults with same-day measures of ACR and PCR or dipstick protein. Measurements: Equations to convert urine PCR and dipstick protein to ACR were developed and tested for purposes of CKD screening (ACR, ≥30 mg/g) and staging (stage A2: ACR, 30 to 299 mg/g; stage A3: ACR, ≥300 mg/g). Results: Median ACR was 14 mg/g (25th to 75th percentile of cohorts, 5 to 25 mg/g). The association between PCR and ACR was inconsistent for PCR values less than 50 mg/g. For higher PCR values, the PCR conversion equations demonstrated moderate sensitivity (91%, 75%, and 87%) and specificity (87%, 89%, and 98%) for screening (ACR, >30 mg/g) and classification into stages A2 and A3, respectively. Urine dipstick categories of trace or greater, trace to +, and ++ for screening for ACR values greater than 30 mg/g and classification into stages A2 and A3, respectively, had moderate sensitivity (62%, 36%, and 78%) and high specificity (88%, 88%, and 98%). For individual risk prediction, the estimated 2-year 4-variable kidney failure risk equation using predicted ACR from PCR had discrimination similar to that of using observed ACR. Limitation: Diverse methods of ACR and PCR quantification were used; measurements were not always performed in the same urine sample. Conclusion: Urine ACR is the preferred measure of albuminuria; however, if ACR is not available, predicted ACR from PCR or urine dipstick protein may help in CKD screening, staging, and prognosis.

Medical records-based chronic kidney disease phenotype for clinical care and “big data” observational and genetic studies

“… The 95% confidence intervals were calculated based on 10-fold cross-validation; DSP Scale 1: reported as Negative, Trace, 1 + , 2 + , 3 + , 4 + ; DSP Scale 2: reported as Negative, Trace, 10, 30, 100, 300, or ≥ 300; only the performance of the final pooled classifiers across Columbia University, University of Minnesota, and Vanderbilt University are summarized, for detailed breakdown of site-specific performance see Tables S1 – S5 , and for additional validation studies and comparisons with recently published methods by Sumida et al 24 , see Table S6 . …”

“…To further test our A-stage prediction, we compared the performance of our classifiers to the alternative methods developed more recently by the CKD Prognosis Consortium 24 (Supplementary Table 6 ). Based on an independent testing dataset, we demonstrated that the performance of the two methods was generally comparable.…”

Adherence to the Kidney Disease: Improving Global Outcomes CKD Guideline in Nephrology Practice Across Countries

“…In addition, the availability of an equation to convert protein-to-creatinine ratio to albumin-to-creatinine ratio makes the latter easier and cheaper to estimate. 42 Of note, although the protocol used in France to achieve albuminuria measurement cannot be implemented routinely, we can speculate that the use of standard protocols and laboratory test prescriptions managed by nurses may improve adherence to recommendations.…”

Sodium Intake and Proteinuria/Albuminuria in the Population—Observational, Cross-Sectional Study

“…The regression coefficient of diabetes to ACR was 2.4 times higher in comparison to PCR and 5.1 times higher in comparison with non-albumin proteins, in accordance with the concept that high albuminuria is a key marker of diabetic kidney dysfunction [ 43 ]. Moreover, the difference in the regression coefficients of diabetes with PCR and ACR indicated that the relation between PCR and ACR could differ between diabetics and nondiabetics [ 44 ]. Last, the inverse relation of serum 25(OH)-vitamin D with urinary ACR could reflect mechanism(s) similar to those proposed for anti-proteinuric effects of vitamin D supplementation [ 31 ].…”