Comparison of haemoglobin H inclusion bodies with embryonic ζ globin in screening for α thalassaemia

Abstract

Aims - To compare the haemoglobin (Hb) H inclusion test with immunocytochemical detection of embryonic ζ chains in screening for a thalassaemia. Methods - Blood samples from 115 patients with relevant clinical history and hypochromic microcytic indexes were screened using the HbH inclusion test and the Variant Hemoglobin Testing System (BioRad, Hercules, CA, USA). Results - The HbH inclusion test was positive in 61 of 115 cases, three of whom had HbH disease confirmed by electrophoresis. The remaining 58 had α thalassaemia 1. All three HbH cases and 56 of 58 cases of a thalassaemia 1 expressed embryonic ζ chains, giving a specificity of 96.7%. Fifty four of 115 cases had a negative HbH inclusion test, of whom 50 had β thalassaemia trait and three had iron deficiency. No diagnosis was reached for the remaining patient. Conclusion - The immunocytochemical test is as sensitive as the HbH inclusion test in screening for a thalassaemia. The presence of ζ chains is highly specific for a thalassaemia I incorporating the (--/SEA) deletion. The specificity and simplicity of the immunocytochemical test make it the test of choice in screening for α thalassaemia.