Table 1 Inclusion and exclusion criteria

Patients diagnosed with thalassemia.

Patients having impaired cognitive function or having severe clinical condition, which may limit their ability to participate in the study.

Patients between 5 and 18 years of age.

Patients taking oral iron overload treatment.

Patients who had been treated at Phramongkutklao Hospital, King Chulalongkorn Memorial Hospital or Saraburi Hospital since October 1, 2004.

Patients unwilling to participate in the study.