PRENATAL DIAGNOSIS OF Â-THALASSAEMIA: EXPERIENCE IN A DEVELOPING COUNTRY

Authors: RENU SAXENA, PAWAN K. JAIN, ELIZABETH THOMAS AND ISHWAR C. VERMA*
Genetic Unit, Department of Pediatrics, World Health Organization Collaborating Center in Genetics,
All India Institute of Medical Sciences, New Delhi, India

SUMMARY
We present our experience with the amplification refractory mutation system (ARMS) for the prenatal diagnosis
of â-thalassaemia in 415 pregnancies of 360 women. Five mutations of the â-thalassaemia gene common in
Asian Indians accounted for 89·2 per cent and rare mutations for 7·2 per cent of all mutant chromosomes, while
3·3 per cent of chromosomes remained uncharacterized. Identical mutations were present in both parents in
43·2 per cent of cases, due to caste-based marriages in India. A confirmed diagnosis was given in 401 (98·3 per cent)
cases, of which a complete diagnosis (whether the fetus was normal, a carrier, or homozygous) was possible in 391
(94·2 per cent) of the cases. In 15 couples, the mutation was identified in only one parent. In nine of these, the
identified mutation was not present in the fetus, predicting normal/carrier status, while in five the identified mutation was present in the fetus, suggesting carrier/affected status. The abortion rate was 3·9 per cent. Pitfalls in diagnosis were failure of oligonucleotides to work, maternal contamination, and false paternity. The ARMS provides an inexpensive, robust and non-isotopic method for the prenatal diagnosis of â-thalassaemia in India. Recommendations are outlined for establishing a prenatal diagnostic service in developing countries