Original Paper Acta Haematol 2002;108:8–12 Routine Screening of (-- SEA ) ·-Thalassemia Deletion by an Enzyme-Linked Immunosorbent Assay for Embryonic ˙-Globin Chains S.K. M a a Victor Ma a Amy Y.Y. Chan a L.C. Chan a David H.K. Chui b a Division of Hematology, Department of Pathology, University of Hong Kong, Queen Mary Hospital, Hong Kong, China; b Provincial Hemoglobinopathy Laboratory, Department of Pathology and Molecular Medicine, Faculty of Health Sciences, McMaster University, Hamilton, Canada Received: August 10, 2001 Accepted after revision: November 23, 2001 Dr. S.K. Ma Division of Hematology, Department of Pathology University of Hong Kong, Queen Mary Hospital 102 Pokfulam Road, Hong Kong (China) Tel. +86 852 2855 4570, Fax +86 852 2817 7565, E-Mail edmond@pathology.hku.hk ABC Fax + 41 61 306 12 34 E-Mail karger@karger.ch www.karger.com © 2002 S. Karger AG, Basel 0001–5792/02/1081–0008$18.50/0 Accessible online at: www.karger.com/journals/aha Key Words ELISA W Embryonic ˙-globin chains W SEA deletion W Thalassemia screening W ·-Thalassemia Abstract We evaluated an enzyme-linked immunosorbent assay (ELISA) for embryonic ˙-globin chains as a routine screening test for (-- SEA ) ·-thalassemia deletion (SEA deletion). A total of 174 consecutive patient samples with a request for Hb analysis were recruited. The ELISA method was evaluated against a polymerase chain reac- tion (PCR)-based technique that was taken as the stan- dard. Among 56 simple carriers of SEA deletion diag- nosed by PCR and 112 subjects without the SEA deletion, the sensitivity and specificity of the ELISA method was 89.3–96.4 and 98.2–100%, respectively, depending on the cutoff value for optical density that was adopted. The ELISA method was able to detect both subjects with SEA deletion and concurrent ß-thalassemia trait in this series, but only 1 out of 4 patients (25%) with Hb H disease. We speculate that incomplete lysis of hypochromic micro- cytic red cells together with the low red cell count in Hb H disease might account for the false-negative results. We showed that the ELISA method for embryonic ˙-chains was a sensitive method of screening for SEA deletion carriers at our locality, and should be easily adopted in a routine diagnostic laboratory. The method was rapid and also amendable to automation. In areas with a high prev- alence of ·-thalassemia, improved detection of SEA de- letion carriers would ultimately facilitate the identifica- tion of pregnancies at risk of hydrops fetalis and its pre- vention through prenatal diagnosis. Copyright © 2002 S. Karger AG, Basel Introduction The SEA deletion, the commonest mutation causing ·-thalassemia in Hong Kong, has a prevalence of 4.5% at our locality [1]. Carrier detection is important so that pre- natal diagnosis may be offered to couples at risk of con- ceiving a fetus affected by hydrops fetalis [2]. Currently SEA deletion carriers, who usually do not have significant anemia but show hypochromic microcytic red cell in- dices, may be detected by three methods, each having its own limitations. Firstly, the search for Hb H inclusion bodies, tetramers of ß-chains present in excess in these