Abstract Screening for undetected ß globin gene mutations using chemical cleavage of mismatch method in patients registered with the Thalassaemia Registry, University Hospital Kuala Lumpur

M.K. Thong^1*, Z. Rudzki² ,J. HaIl², S. F. Yap³, KL. Tan³ and J.A.M.A. Tan³

¹Department of Paediatrics and ²Department of Allied Health Sciences, Faculty of Medicine,
University of Malaya, 50603 Kuala Lumpur, Malaysia . ³The Molecular Pathology Unit,
Institute of Medical and Veterinary Science, Frome Road, SA 5000, Australia.

(Received 7 December 1998 / Accepted 12 February 1999)

Abstract.
Advances in molecular diagnostic techniques have resulted in the characterisation of over 200 mutations causing ß thalassaemia. In addition, each population appears to have its own unique set and frequency of ß globin gene mutations. The strategy for prenatal diagnosis therefore involves screening at risk couples for the most common mutations known to be present in the ethnic group or population. As a result of this selective approach, uncommon or novel mutations are not detected. We undertook to characterise B globin gene mutations which remain undetected following polymerase chain reaction (PCR) and amplification refractory mutation system (ARMS) analyses. In this study, we successfully identified 13 of the 16 'unknown' alleles using chemical cleavage of mismatch (CCM) method and direct sequencing. As a result of this coupled strategy (ARMS and CCM), 98.5% of the ß globin gene mutations in the Thalassaemia Registry, University Hospital Kuala Lumpur were characterised.

Keywords: ß thalassaemia, chemical cleavage of mismatch, uncommon mutations, mutation detection