Glomerular Hyperfiltration in Adult Sickle Cell Anemia: A Frequent Hemolysis Associated Feature

Sickle cell anemia-associated nephropathy is a growing matter of concern because renal failure affects most aging sickle cell anemia patients. Glomerular damage is a common feature revealed by a microalbuminuria or a macroalbuminuria. Although glomerular hyperfiltration has been described for decades in this population, its prevalence in young adults is unknown. To address this issue, as well as the clinical and biologic correlates of hyperfiltration, a single-center, cross-sectional study of 280 homozygous SS disease patients was performed. The prevalence of hyperfiltration assessed by Modification of Diet in Renal Disease estimated GFR was 51%. Among patients with hyperfiltration, 49% had hyperfiltration alone, whereas 36% and 15% had an associated microalbuminuria or macroalbuminuria, respectively. Estimated GFR sensitivity and specificity for hyperfiltration were 94% and 63%, respectively, in a selected subgroup of 48 patients (measured GFR was assessed by urinary (51)Cr EDTA clearance). In patients with no albuminuria, hyperfiltration status was significantly associated with a young age (years), the absence of alpha thalassemia, a lower hemoglobin level (g/dl), and a lower fetal hemoglobin. The role of chronic hemolysis was further strengthened by multivariate analysis showing a correlation between estimated GFR and a low plasma fetal hemoglobin level, a young age, and a high reticulocyte count (r(2) = 0.54). Together, the data suggest that the pathophysiology of hyperfiltration would rather be attributable to the hemolysis-associated vasculopathy rather than a viscosity-vaso-occlusive process.