Non-Invasive Urinary Markers of Renal Dysfunction in Sickle Cell Disease.

Abstract 4621

Renal failure is one of the major complications of sickle cell disease (SCD), affecting 5-18% of the patients. Microalbuminuria (MA), which has a prevalence of 26.5% in all children with SCD, is used as a marker of preclinical glomerular damage and renal disease progression. However, measuring MA alone may miss renal damage involving tubular proteins. We hypothesize that sickle cell nephropathy subjects will have increased urinary excretion of Transforming Growth Factor Beta-1 (TGF β1) and Neutrophil Gelatinase–Associated Lipocalin (NGAL) as compared to age-matched controls (CTR). We also hypothesize that urinary excretion of these proteins will be associated with severity of anemia in SCD. Enzyme-Linked Immunosorbent Assay (ELISA) kits were used to detect urinary excretion of TGF β1/NGAL, and corrected to urine creatinine. Mean age, gender, and race were not statistically different among the groups. Urinary excretion of TGF β1 was significantly higher in SCD subjects (26.4 pg/mg Cr +/-1.5) vs. CTR (14.9 pg/mg Cr +/-2.4), (p<0.00001). There was no difference in urinary NGAL between the SCD subjects vs. CTR. SCD patients with hemoglobin less than 9gm/dl had higher urinary TGF β1 than SCD patients with milder anemia (p=0.002). Urinary TGF β1 was lower in SCD patients on hydroxyurea (23.61+/-2.6), vs. those who were (27.69+/-1.8), p=0.08. Surprisingly, there were no correlation between urinary TGF β1 and urinary microalbumin or estimated glomerular function, indicating that microalbuminuria and serum creatinine are poor measures of renal injury in SCD patients.

Our data suggests that urinary TGF β1 may serve as a urinary biomarker to monitor the progression of renal disease in SCD. This assumption needs to be tested prospectively.