Risk factors for CKD stage II onset in a prospective cohort of homozygous sickle cell adults

Prevalence of renal impairment is increasing with aging in sickle cell anemia (SCA) patients, and is responsible for a high morbidity and mortality. However, sickle cell nephropathy's natural course remains mostly unknown. We conducted a prospective observational cohort study aimed to identify risk factors for CKD stage II in a cohort of SCA patients. Baseline clinical and biological parameters were collected. Renal parameters were updated at each visit. Risk factors were analyzed using the Cox model. Five-hundred and thirty-five SCA patients were included with a median follow-up of 5.33 (IQR:2.10–8.13) years. Median age was 22 (IQR:19–30) years old. Glomerular hyperfiltration was detected in 299 (55.9%) patients, microalbuminuria and macroalbuminuria in 180 (34%) and 67 (12.7%) patients respectively. During follow up, CKD stage II onset was detected in 39 patients (7.3%). Risk factors for CKD stage II after adjustment on baseline eGFR and age were macroalbuminuria HR: 3.89 [95% CI: 1.61;9.43], diastolic blood pressure (DBP) above 70 mm Hg HR: 2.02 [1.02–3.971], LDH (for 100 IU/L increase) HR: 1.28 [1.12;1.48] and tricuspid regurgitation velocity >2.5 m/sec HR: 2.89 [1.20–6.99]. Multivariate analysis also found age as a strong independent risk factor with HR: (per year increase) 1.13 [1.09;1.16] and a 13.3-fold increase above 30 years (p < 0.001). Our results show a high incidence of CKD stage II with aging, with a strong significant risk increase after 30-years-old, and pinpoint baseline DBP, macroalbuminuria and increased LDH as independent risk factors raising the issue of optimal blood pressure targets for SCA patients.