The prevalence of hypertension and abnormal kidney function in children with sickle cell disease -a cross sectional review

Background: Renal disease is a known contributor to mortality in adults with sickle cell disease (SCD) and renal abnormalities are evident in childhood. Hyperfiltration (evidenced by elevated glomerular filtration rate, GFR) occurs in children with SCD early in disease. However, the incidence of low GFR (< 90 ml/min/1.73 m(2)) suggestive of chronic kidney disease (CKD), is not well established. The prevalence of hypertension is also not well known. The goal of this study was to determine the prevalence of hypertension and CKD in a cohort of children with SCD. Methods: We performed a retrospective chart review of patients followed at the Rainbow Babies and Children's Sickle Cell Disease Clinic who were seen during routine follow up visits. Inclusion criteria were all patients ages 3-18. Exclusion criteria included recent (within 2 weeks) hospitalization and/or episode of acute chest, pain crises, febrile illness or red blood cell transfusion. Data collected included serum creatinine, blood pressure and history of sickle cell complications (acute chest syndrome, stroke or stroke risk). Estimated GFR (eGFR) was calculated using the updated Schwartz creatinine-based estimating formula. Analysis examined the associations among eGFR, blood pressure and sickle cell complications. The Institutional Review Board at University Hospitals Case Medical Center approved this study. Results: A total of 48 children had complete data available. Mean eGFR was 140 mL/min/1.73 m(2) +/-34.9 (range 71.9-404.2 mL/min/1.73 m(2)). Four patients (8.3%) had eGFRs < 90 mL/min/1.73 m(2), 35 patients (72.9%) had eGFRs > 120 mL/min/1.73 m(2) and 9 patients (18.8%) had eGFRs in the normal range. Eight patients (16.7%) had evidence of elevated blood pressures (pre-hypertension or hypertension). There was no correlation between eGFR and age, and no association of eGFR with acute chest or stroke risk. Conclusion: In this SCD cohort, we identified abnormally low eGFR (suggestive of early CKD) in 8.3% of patients and elevated blood pressure in 16.7%. These findings are in contrast to other published studies that show primarily normal or elevated GFR and the absence of or minimal hypertension. These findings indicate that elevated blood pressure and decreased eGFR are not uncommon in children with SCD, and should be more rigorously studied.