Prenatal diagnosis of β‐thalassemia in Southern Punjab, Pakistan

Abstract

Pakistan has a large population of more than 150 million people with an overall carrier frequency of approximately 5.6% for beta-thalassemia. Punjab is the largest province of the country having more than 50% of the population. The state of beta-thalassemia is alarming as consanguinity is very high (>81%) and the literacy rate is low in South Punjab. A thalassemia prevention program is the need of the hour in this part of Pakistan. In this study, we initiated awareness, screening, and characterization of the mutations causing beta-thalassemia as well as a genetic counseling program mainly in the districts of Faisalabad and D.G. Khan to establish prenatal diagnosis, a facility previously unavailable in this region for disease prevention. A total of 248 unrelated transfusion-dependent children and the available members of their families were screened to characterize the mutations and identify the carriers. Genetic counseling was provided to these families and prenatal diagnosis offered. In the samples analyzed, 11 beta-thalassemia mutations and three hemoglobin variants were detected mainly by using the Monoplex and Multiplex ARMS-PCR. First-trimester prenatal diagnosis was carried out through chorionic villus sampling (CVS) in seven pregnancies at risk. As a result of our campaign, 145 carrier couples planning to have more children gave their consent to have retrospective prenatal diagnosis in every pregnancy in future. A cooperative trend and a positive attitude toward the prevention of beta-thalassemia were noticed in the families with affected children and in the general population.

Understanding Beta-Thalassemia with Focus on the Indian Subcontinent and the Middle East

“…Regional differences in prevalence across north, east and south India, has also been demonstrated [48]. Within the Northern states, including Punjab, the mutations and allele frequencies are quite similar to those of Pakistan where the two most com- mon mutations were c.92+5G>C (43.5%) and c.27_28insG (38.5%) [47]. The similarity in mutation frequencies in these regions reflects their geographical proximity.…”

“…The similarity in mutation frequencies in these regions reflects their geographical proximity. In addition, 6.6% of confirmed cases in northern India harbored the HBB c.124_127delTTCT mutation [47]. Within the Eastern region of India, including the state of West Bengal, the frequency of HBB c.92+5G>C was 48.8% [49].…”

“…In contrast, RDB involves amplification and biotinlabeling of the DNA sequence of interest, followed by hybridization of the amplified products to oligonucleotide probes immobilized on a membrane [63]. Indeed in many studies, fetal DNA from chorionic villus sampling was screened tests including ARMS-PCR method and by RDB analysis [47][48][49][50]. Once fetuses were diagnosed, the option of pregnancy termination can be offered, within the boundaries of consideration given to appropriate cultural and ethical sensitivities.…”

“…They are presently not ideal for economically-unstable countries within Indian Subcontinent and the Middle East. Therefore, the strategy of developing dedicated allele-specific methods to find the most prevalent geographically-relevant mutations causing beta-thalassemia based on screening for a small number of known mutations that underlie a majority of cases is a more realistic goal [47].…”

“…In beta-thalassemia patients from Pakistan, there was a high consanguinity rate (81%) [47,48]. The polymorphism at c.92+5G>C, in the HBB gene, was the most common mutation (37.0%), followed by c.27_28insG and 619bp deletion with allele frequencies of 21.0% and 12.0%, respectively [48] (Table 1).…”