A-195 Evaluating Albuminuria and Total Proteinuria in Chronic Kidney Disease: ACR-PCR Agreement and Practice Implications Under KDIGO 2024

Abstract

The 2024 Kidney Disease: Improving Global Outcomes (KDIGO) Guideline for the Evaluation and Management of Chronic Kidney Disease (CKD) reinforces albuminuria assessment using the albumin to creatinine ratio (ACR) as a core requirement for CKD detection, CGA classification, and risk stratification, given its superior prognostic value compared with urine protein to creatinine ratio (PCR). KDIGO additionally emphasizes that dipstick protein is suitable for screening but must be confirmed by quantitative testing. The aim of the study is to assess the agreement between ACR and PCR for proteinuria evaluation and determine how their concordance and discordance align with KDIGO 2024 recommendations for CKD assessment. We analyzed random urine samples from 42 CKD patients (age 23-92, 23 female and 19 male) with quantitative urine albumin, urine protein, urine creatinine, ACR, PCR, dipstick urine protein, serum creatinine, and eGFR. Paired ACR and PCR values were categorized using standard thresholds: ACR <30, 30–300, >300 mg/g; PCR <150, 150–500, >500 mg/g. Agreement statistics included observed agreement and Cohen’s k. Continuous associations were evaluated using Pearson correlation of log10 transformed values and Spearman rank correlation. ACR categories were distributed as 14 normal, 16 moderately increased, and 12 severely increased; PCR categories as 10, 16, and 16, respectively. Observed agreement between ACR and PCR categories was 81% (95% CI 69.0-92.9%), with Cohen’s k = 0.714 (95% CI 0.525-0.889), indicating substantial agreement. Discordance occurred in 19% (95% CI 7.1-31.0%), exclusively due to PCR assigning one category higher; no ACR higher or two step discrepancies were observed. Continuous ACR and PCR values were strongly correlated (Spearman correlation Rs = 0.924, p < 0.001). Dipstick urine protein showed a stepwise increase across proteinuria severity, with PCR medians ranging from 234.6 to 2779.3 mg/g and ACR medians from 14.9 to 2185.6 mg/g. Correlation between dipstick urine protein and quantitative measures was high (Rs = 0.736-0.772). Across eGFR stages, severe proteinuria became most prevalent in G4-G5, although substantial albuminuria was already present in G2. eGFR correlated weakly and non-significantly with ACR (Rs = -0.177) and PCR (Rs = -0.157). Our findings mirror several key principles highlighted in the 2024 KDIGO CKD Guideline. First, although ACR and PCR demonstrate substantial agreement, their 19% discordance supports KDIGO’s position that ACR and PCR are not interchangeable. PCR’s tendency to stage higher reflects the contribution of non-albumin urinary proteins, consistent with KDIGO’s guidance that PCR is most informative when tubular or overflow proteinuria is suspected. Second, ACR’s strong alignment with dipstick gradients and its independence from eGFR reinforce its central role in KDIGO’s CGA classification and risk prediction framework. Third, the weak correlation between proteinuria indices and eGFR parallels KDIGO’s emphasis that albuminuria and GFR capture distinct dimensions of CKD risk. Collectively, these findings support the KDIGO recommended approach of using ACR as the primary quantitative marker for CKD staging and therapeutic decision making, with PCR as a complementary test to capture non-albumin proteinuria and refine clinical interpretation of dipstick positivity.