Study population

A non-probable sampling was made for this study. Initially, 350 thalassemia major subjects of different age groups were recruited from transfusion centers in Lahore, Multan, Karachi and Peshawar (162 from Lahore, 64 from Multan, 71 from Karachi and 53 from Peshawar) between December 2011 and December 2013. At these centers, instead of whole blood, specific blood components (red cells) are transfused at an optimized dose, using Thalassemia International Federation guidelines. Red cells are stored at an optimum temperature (4 °C). This study was performed according to the World Medical Association (Declaration of Helsinki) code of ethics. Approval for this study was obtained from the Ethics committee of the School of Biological Sciences, University of the Punjab, Lahore, Pakistan.