Important clinical and laboratory correlates of glomerular filtration rate in sickle cell anemia

Renal impairment is routinely assessed using the estimated glomerular filtration rate (eGFR) and it may be helpful to obtain certain clinical or laboratory markers, which show relationship with glomerular filtration rate (GFR) in sickle cell disease (SCD).

To assess the relationship between important clinical and laboratory parameters in SCD, and the eGFR.

Steady state clinical and laboratory data were obtained from 228 homozygous SCD patients seen over a 7-year period. The GFR was estimated using (isotope dilution mass spectrometry) traceable modification of diet in renal disease (MDRD) and Cockroft-Gault methods. The correlation coefficient and independent t-test were done to assess the level of significance between the eGFR_MDRD and the known indicators of disease severity.

The serum alkaline phosphatase (ALP) and serum direct bilirubin levels both showed significant inverse relationship with eGFR_MDRD P = 0.012 and P = 0.24, respectively. The patients' age, Hb, leukocyte count, platelet count, serum direct bilirubin and aspartate transaminase did not show a significant correlation. The eGFR_MDRD was more discriminatory revealing that 20.3% of the patients had suboptimal GFR. Proteinuria in steady state was observed in 20.3% of the patients.

High serum direct bilirubin and ALP are associated with a deteriorating eGFR_MDRD. Other clinical and laboratory indicators of disease severity in SCD do not show the relationship with the GFR. MDRD_GFR estimation seemed to be a more appropriate method of estimating GFR in SCD.