PRENATAL DIAGNOSIS OF Β-THALASSEMIA: 12 YEARS’ EXPERIENCE AT A SINGLE LABORATORY IN PAKISTAN

Author: Suhaib Ahmed
Department of Haematology, Armed Forces Institute of Pathology, Rawalpindi, Pakistan

Objective To evaluate the service for prenatal diagnosis of β-thalassemia in Pakistan.
Methods All prenatal diagnoses (PNDs) for β-thalassemia since the introduction of the service in 1994 were
studied. PND was done by the Amplification Refractory Mutation System (ARMS), or linkage analysis, when
required. The reported errors in PND were investigated for clerical mistakes, technical problems with PCR,
maternal contamination and nonpaternity.

Results In the 12 years 2174 PNDs were done for β-thalassemia at the country’s main referral center. The
use of PND has increased from 26 in 1994 to 381 in 2006. Over 97% of the couples who requested PND
already had an affected child. In over 97% of the cases PND was done by direct mutation analysis. The
reported rate of misdiagnosis was 0.37%. The causes of misdiagnoses included one clerical mistake, three
false positive PCR results, and two maternal contaminations in the chorionic villus sampling (CVS).

Conclusion PND for β-thalassemia is technically feasible by direct mutation analysis in most cases in
Pakistan. The procedure is quick and cost effective. Strict quality assurance can achieve an acceptably low
error rate. Copyright  2007 John Wiley & Sons, Ltd.