COMPARISON OF HEMOGLOBIN-H INCLUSION-BODIES WITH EMBRYONIC ZETA-GLOBIN IN SCREENING FOR ALPHA-THALASSEMIA

Aims-To compare the haemoglobin (Hb) H inclusion test with immunocytoc hemical detection of embryonic zeta chains in screening for alpha thal assaemia. Methods-Blood samples from 115 patients with relevant clinic al 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 electrophores is. The remaining 58 had alpha thalassaemia 1. All three HbH cases and 56 of 58 cases of alpha thalassaemia 1 expressed embryonic zeta chain s, giving a specificity of 96.7%. Fifty four of 115 cases had a negati ve HbH inclusion test, of whom 50 had beta thalassaemia trait and thre e had iron deficiency. No diagnosis was reached for the remaining pati ent. Conclusion-The immunocytochemical test is as sensitive as the HbH inclusion test in screening for alpha thalassaemia. The presence of z eta chains is highly specific for alpha thalassaemia 1 incorporating t he (--/SEA) deletion. The specificity and simplicity of the immunocyto chemical test make it the test of choice in screening for alpha thalas saemia.