Soluble Urokinase-Type Plasminogen Activator Receptor in Black Americans with CKD

Background and objectives: Black Americans with and without APOL1 kidney disease risk variants face high risk of ESKD. Soluble urokinase-type plasminogen activator receptor (suPAR), a circulating signaling protein and marker of immune activation, constitutes a promising biomarker of CKD-associated risks. We aimed to quantify the associations between serum suPAR concentration and adverse outcomes in Black Americans with and without APOL1 kidney disease risk variants, over and above iodine-125 iothalamate measured GFR and proteinuria.

Design, setting, participants, & measurements: Using data from the African-American Study of Kidney Disease and Hypertension, a multicenter clinical trial followed by a cohort phase with a median total follow-up of 9.7 years (interquartile range, 6.5-10.9 years), we examined the associations of suPAR with CKD progression (defined as doubling of serum creatinine or ESKD), ESKD, worsening proteinuria (defined as pre-ESKD doubling of 24-hour urine protein-to-creatinine ratio to ≥220 mg/g), and all-cause death.

Results: At baseline, the median suPAR was 4462 pg/ml, mean measured GFR was 46 ml/min per 1.73 m², and median 24-hour urine protein-to-creatinine ratio was 80 mg/g. After controlling for baseline demographics, randomization arm, GFR, proteinuria, APOL1 risk status, and clinical risk factors, there was a 1.26-times higher risk for CKD progression per SD higher baseline log-transformed suPAR (hazard ratio [HR], 1.26; 95% confidence interval [95% CI], 1.11 to 1.43; P<0.001). Higher suPAR was also independently associated with risk of ESKD (HR, 1.36; 95% CI, 1.17 to 1.58; P<0.001) and death (HR, 1.25; 95% CI, 1.08 to 1.45; P=0.003). suPAR was only associated with worsening proteinuria in patients with two APOLI risk alleles (HR, 1.46; 95% CI, 1.08 to 1.99; P=0.02).

Conclusions: Higher suPAR was associated with various adverse outcomes in Black Americans with CKD, with and without APOL1 kidney disease risk variants, independently of proteinuria and GFR.