Background Relative iron deficiency is common among Tetralogy of Fallot (TF) patients and is resulted by inadequate iron supplies for erythropoiesis. The compensatory mechanism is ineffective because the high-elevated hematocrit levels is not accompanied by an increase in oxygen binding capacity.

Objective To observe the decrease in hematocrit levels post iron therapy in TF patients with relative iron deficiency.

Methods This prospective study was carried out in the pediatric cardiology outpatient clinic and pediatric ward Dr. Soetomo Hospital for 6 months. Study population is TF patients that came to the pediatric cardiology outpatient clinic and ward. Patients who fulfilled the study criteria then had venous blood examination for serum iron and total iron binding capacity. Transferin saturation was calculated according to Dallman equation

Result From 40 patients who qualified for the study criteria, 20 patients acted as the control group with transferin saturation >11.5, while 20 acted as treatment group with transferin saturation <11.5. The pre treatment hematocrit level in the control group ranged between 35.2 and 58.2 (mean of 47.7), while in the treatment group the range was between 38.5 and 74.4 (mean of 60.8). The t-test result showed significant differences in pre treatment hematocrit levels between the control group and the treatment group (P value<0.005). The hematocrit level after treatment was lower than before treatment. Paired t-test result showed significant changes in hematocrit levels before and after treatment (p value <0.05).

Conclusion The iron therapy can lower hematocrit level in TF patients with relative iron deficiency.