Supplementary Material for: Best Albuminuria Measurement to Predict Cardiovascular and Renal Events

Background: Kidney Disease Improving Global Outcomes (KDIGO) guidelines encourage clinicians to estimate 24-hour albuminuria as albumin to creatinine ratio (ACR) from spot urine samples. However, ACR underestimates 24-hour albumin excretion in muscular individuals. Equations that adjust ACR for surrogates of muscle mass to yield an estimated albumin excretion rate (eAER) were developed. We hypothesised that eAER is a better predictor of cardiovascular and renal outcomes than ACR. Methods: We determined ACR and eAER among 443 patients with chronic kidney disease G2-G4 recruited into the CARE FOR HOMe study. Patients were classified into KDIGO albuminuria categories, and followed for cardiovascular and renal events. The primary analysis was the net reclassification improvement (NRI) for those with and without events within 3 years of follow-up. Results: Eighty five patients experienced cardiovascular events during 3 years of follow-up, 13 of whom were reclassified to a more advanced albuminuria category, and 1 patient to a less advanced category by eAER compared to ACR (NRI_event: 14.1% (95% CI 5.8-22.4)). Among 358 patients without a cardiovascular event, 17 patients were reclassified to a more advanced albuminuria category, and 2 patients to a less advanced category by eAER (NRI_{no event}: -4.2%, 95% CI -8.5 to -1.8). Sixty patients went through renal events, and 383 patients had event-free 3-year follow-up. NRI_event was 6.7% (95% CI -1.2 to 14.5), and NRI_{no event} was -6.0% (95% CI -10.6 to 3.4) for renal events. Conclusion: Compared to ACR albuminuria categories, eAER categories are better associated with future cardiovascular events, but not with renal events.