The Value of Beta2 Microglobulin, Retinol Binding Protein, Endothelin-1, N Amino ß-d-Glucoaminodase and Cystatin C for the Evaluation Sickle Cell Nephropathy

Sickle Cell Anemia (SCA) is a chronic disease characterized by broad clinical manifestations and multi-organ disease. Sickle cell nephropathy is one of the major side effects in the patients with SCA. This study was planned to determine the incidence of renal complications of the patients with SCA and to evaluate the renal complications by using new markers such as ß2 microglobulin, retinol binding protein (RBP), endothelin-1, N amino ß-d-glucoaminodase (NAG) and cystatin C.

45 children (mean age 8.4 ± 1.21, range: 1–15 years), 10 adult patients with SCA (mean age:31.4 ± 10.11, range: 16–45 years) and 20 healthy children (mean age:8.45 ± 4.05, range: 1–15 years), 10 healthy adults (mean age: 26.6 ± 8.62, range: 16–45 years) as control groups were included in the study. A detailed history was taken from each child, and a full physical examination was performed. Serum and urine electrolytes, urine analysis, urine culture and renal ultrasonography were performed for all patients. 24 hour urine was collected both in patient and control groups, and GFR was measured. Tubular phosphate reabsorbtion, 24 hour urine protein and calcium excretion, fractional excretion of Na, K, Urea and Cl were calculated from 24 hour urine samples. ß2 microglobulin, endothelin-1 RBP and NAG levels were measured in spot urine samples of patients and controls. Serum cystatin C level was measured in both patient and control groups. ß2 microglobulin, endothelin-1, RBP and cystatin C were measured with micro-elisa method. On the other hand colorimetric assay was used to measure NAG.

35 patients (63%) had enuresis nocturna, 34 patients (61%) had moderate proteinuria and 9 patient (16%) had poliuria. 26 patients (47%) had past history of urinary tract infection and 3 patients had past history of hematuria. Although all the markers to evaluate tubular functions were in normal ranges, ß2 microglobulin/creatinine ratio was found to be high in 10 patients (18%). GFR measured with creatinine was in normal ranges in all of the patients. Hovewer GFR measured with cystatin-C was low in 3 patients (0.5%). Urine ß2 microglobulin, endothelin-1, RBP, NAG, and serum cystatin-C levels were all in normal ranges both in patient and control groups.

The commonly observed renal side effects in the patients with SCA are enuresis nocturna, proteinuria and increased tendency to urinary tract infections. It could be suspected that ß2 microglobulin/creatinin ratio and GFR that is calculated by the use of cystatin C could be use in order to evaluate the tubular and glomerular functions in those patients with SCA during the early stages of sickle cell nephropathy. Besides, urine endothelin-1, RBP and NAG levels could not be considered as good markers for determining the sickle cell nephropathy.

No relevant conflicts of interest to declare.