Prenatal control of severe thalassaemia: Chiang Mai strategy

Prenatal diagnosis of severe thalassaemia is conventionally diagnosed by fe tal DNA analysis but it can not be widely used due to its drawbacks of high cost and technical effort. This prospective study describes a new prenatal strategy in preventing severe thalassaemia by a more simple and inexpensiv e way. The strategy included: (1) genetic counselling; (2) identification o f pregnancies at risk by retrospective screening (history of known risk) an d prospective screening for asymptomatic women; (3) cordocentesis at 16 22 weeks' gestation; (4) fetal blood analysis with high performance liquid chr omatography (HPLC); (5) termination of affected pregnancy. The prospective screening consisted of 2 min osmotic fragility (OF) and HbE screening test in women with no risk, and testing the husbands of the women with a positiv e result. If both of the couple had a positive result, the diagnostic test (HbA(2) level and PCR alpha-thal 1) for the carrier was needed. A pregnancy in which both of the couple were carriers was considered at risk. This: st rategy identified 181 and 108 couples at risk by prospective (from 7954 pre gnancies) and retrospective screening, respectively. Two hundred and forty- two underwent cordocentesis, 108 from retrospective screening and 134 from prospective screening, and 62 were proven to have severe thalassaemia (29 a nd 33 in retrospective and prospective screening, respectively). The strate gy identified nearly all, if not all, fetuses with severe thalassaemia with out false positives among the screened couples. Tn conclusion, the strategy proves to be highly effective in the control of severe thalassaemia. Copyr ight (C) 2000 John Wiley & Sons, Ltd.