Renal tubular dysfunction in pediatric patients with beta-thalassemia major

To evaluate the prevalence of renal tubular dysfunction in children with β-thalassemia (β-T) major, we studied the glomerular and tubular function in 140 children with β-T major and compared them to a healthy control group at our center from May 2007 to April 2008. Fresh first morning samples were collected from each patient and analyzed for sodium, potassium, calcium (Ca), protein, uric acid (UA), creatinine (Cr), urine osmolality and urinary N-acetyl-β-D-glucosaminidase (UNAG) activity. Blood samples were also collected for complete blood count, blood urea nitrogen (BUN), fasting blood sugar, serum creatinine (SCr), electrolytes, and ferritin before transfusion. Among the study patients, 72 were males, and the mean age was 11.5 (ranging 7-16) years. SCr levels were all within normal limits and all of them had normal glomerular filtration rate (GFR). The mean UNAG was 17.8 IU/L in the study patients (normal 0.15-11.5 IU/L) and 3.2 IU/L in the control group (P < 0.001). Of the 82 study patients who had elevated level of UNAG, 58 (62.4%) had high blood levels of ferritin also (r = 0.2, P < 0.001) and 13 (15.9%) patients had hypercalciuria also (UCa/UCr > 0.21) (P = 0.006). Nine (6.4%) thalassemic patients with a mean age of 12 years had proteinuria (Upr/UCr > 0.2). Sixty-nine (49.3%) out of the 140 patients and 45 (65.2%) of the patients having UNAG had uricosuria also (UUA/UCr > 0.26). Ten (7%) patients had microscopic hematuria and 10 (7%) patients with a mean age of 13.5 years had glucosuria or diabetes mellitus. We conclude that tubular dysfunction is a relative common complication of the β-T major; UNAG and its index are the best to detect renal tubular dysfunction in these patients. Currently, periodic measurement of UCa/UCr and UUA/UCr ratios as well as urinalysis are recommended.