Diagnostic Accuracy of Rdwi to Differentiate Iron Deficiency Anemia and Thalassemia Trait in Borderline Hba2

Abstract

Background: Thalassemia is an inherited hemoglobin disorders in which there is reduction or absence of α or β chains due to mutations in α or β genes. Microcytic hypochromic anemia is hallmark of beta thalassemia trait and the patient is usually asymptomatic. It is important to differentiate it from iron deficiency anemia (IDA) which also shows similar peripheral blood picture. The diagnosis is based on quantification of HbA2 and serum ferritin. If the level of HbA2 is more than 3. 5%, then diagnosis of beta thalassemia trait is made. The problem arises with borderline HbA2 i. e 3.1% - 3.4%. There is also diagnostic difficulty when concomitant iron deficiency anemia is present.
 Objectives: To determine the diagnostic accuracy of RDWI in borderline HbA2 to distinguish the beta thalassemia trait from IDA and to diagnose beta thalassemia trait when genetic analysis is not easily available.
 Methods: It was a cross sectional validation study. A total of 90 patients were included in this study, having HbA2 between 3.1-3.4%. Tests for serum ferritin, serum iron and total iron binding capacity (TIBC) were done on all samples. RBC morphology, RBC count, mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC) and RDW of all samples were noted. RDWI of all samples was calculated. Mutational analysis by ARMS- PCR was done for confirmation of β thalassemia trait.
 Results: Out of 90 samples with borderline HbA2, 30 cases were diagnosed as β thalassemia trait. Out of these, 15(50 %) had concomitant IDA along with beta thalassemia trait and 15 were non iron deficient beta thalassemia carriers. 43 samples were not iron deficient and were also negative for β thalassemia trait, whereas 17 samples had only IDA without beta thalassemia trait. The sensitivity of RDWI was 76.6% and specificity was 56.6% in borderline HbA2.
 Conclusion: RDWI is a good indicator to differentiate between IDA and beta thalassemia trait (sensitivity 76.6% specificity 56.6%). But in all cases of borderline HbA2 genetic analysis should be done to see the mutation and to confirm the diagnosis.