# Albuminuria Predicts a Rapid Decline in Kidney Function in 2 International, Longitudinal Cohorts of Adults With Sickle Cell Anemia

## TL;DR

High urine albumin levels predict faster kidney function decline in adults with sickle cell anemia, according to two international studies.

## Contribution

This study shows that uACR is a reliable predictor of kidney function decline in sickle cell anemia patients.

## Key findings

- Higher baseline uACR independently predicted faster eGFR decline in patients with sickle cell anemia.
- A uACR of ≥100 mg/g creatinine was linked to rapid annual eGFR decline in both US and French cohorts.
- Tobacco smoking was associated with faster eGFR decline in both study groups.

## Abstract

Chronic kidney disease (CKD) is common and a major contributor to increased morbidity and early mortality in people with sickle cell anemia (SCA). Urine albumin‐to‐creatinine ratio (uACR) is recommended to identify patients with SCA‐related CKD but its utility in predicting long‐term kidney dysfunction remains unclear in this patient population. In two independent, longitudinal cohorts of patients with hemoglobin SS or Sβ0‐thalassemia (USA: n = 268, median follow‐up 6 years; France: n = 310, median follow‐up 8.2 years) we investigated the utility of uACR, as well as other clinical and modifiable risk factors, for predicting a decline in kidney function as determined by the rate of estimated glomerular filtration rate (eGFR) decline. Using linear mixed‐effects models, a higher baseline uACR independently predicted a faster rate of eGFR decline as well as a more rapid annual eGFR decline, defined as ≥ 3 mL/min/1.73m2 (p ≤ 0.009). Furthermore, baseline uACR of ≥ 100 mg/g creatinine was independently associated with the rate of eGFR decline and rapid annual eGFR decline in both cohorts. Tobacco smoking was also associated with a faster rate of eGFR decline and was congruous between the two cohorts. In conclusion, we demonstrate that uACR is an important clinical tool that predicts a more rapid decline in kidney function and should be routinely monitored in people with SCA. Our data also support preventative care to reduce tobacco smoking for mitigating the risk of CKD progression in this high‐risk population.