Cystatin C levels in patients with beta-thalassemia during deferasirox treatment

Deferasirox (Exjade) is a once-daily, oral iron chelator approved for the treatment of transfusional iron overload. This study was conducted to analyze changes in cystatin C concentration, an endogenous marker of glomerular filtration rate (GFR), in patients with thalassemia receiving daily deferasirox therapy over a period of at least 9 months. One hundred and fifty beta-thalassemia patients were treated with deferasirox at doses of 20-40 mg/kg/day for 9 consecutive months. Cystatin C concentrations were measured at regular intervals and GFR was calculated according to the cystatin C-based prediction equation. Plasma concentrations of NGAL protein and NT-proBNP were also monitored as indicators of renal function and LVEF, respectively. Serum ferritin concentration was also measured to assess iron overload. Throughout the 9 months of deferasirox treatment cystatin C concentration remained stable (p>0.850). The baseline cystatin C mean values were 0.97+/-0.27 mg/L and reached a maximum of 1.01+/-0.29 mg/L at 4 months of treatment. No correlation was found between cystatin C and NGAL concentrations (p>0.674). Cystatin C and NT-proBNP concentrations correlated positively with a binomial equation (p<0.004), as also did cystatin C and serum ferritin (p<0.001). These findings suggest that slight changes of cystatin C during deferasirox treatment may not reflect renal injury. However hemodynamic signals such as LVEF alterations and iron mobilization do appear to affect changes in cystatin C concentration.