Medknow Publications on behalf of Indian Society of Human Genetics
Abstract
Introduction : India is an ethnically diverse country with an
approximate population of 1.2 billion. The frequency of
beta-thalassemia trait (\u3b2TT) has variously been reported from <
1% to 17% and an average of 3.3%. Most of these studies have been
carried out on small population groups and some have been based on
hospital-based patients. There is also a variation in the prevalence of
hemoglobinopathies in different regions and population groups in the
country. A high frequency of Hb D has been reported from the North in
the Punjabi population, Hb E in the eastern region of India and Hb S is
mainly reported from populations of tribal origin from different parts
of the country. Objectives: To study the gene frequency of \u3b2TT
and other hemoglobinopathies in three regions East (Kolkata), West
(Mumbai) and North (Delhi) in larghe population group (schoolchildren)
for a more accurate assessment of gene frequency for planning of
control programmes for haemoglobinopathies. Materials and Methods:
This study included 5408 children from 11 schools in Delhi, 5682 from
75 schools in Mumbai and 957 schoolchildren from Kolkata who were
screened for \u3b2TT and haemoglobinopathies. These included 5684
children from 75 schools in Mumbai and 5408 children from 11 schools in
Delhi. Children were 11-18 years of age of both sexes. The final report
is, however, only on 11090 schoolchildren from Mumbai and Delhi as data
from Kolkata was restricted both in numbers and objectives and could
not be included for comparison. Results: The overall gene frequency of
\u3b2TT in Mumbai and Delhi was 4.05% being 2.68% and 5.47% in
children of the two cities respectively. In Mumbai, the gene frequency
was evenly distributed. Majority of the children with \u3b2TT from
Mumbai were from Marathi (38.9%) and Gujarati (25%) speaking groups.
Gene frequency was> 5% in Bhatias, Khatris, Lohanas and Schedule
Castes. In Delhi, a higher incidence was observed in schoolchildren of
North and West Delhi (5.8-9.2%). The schoolchildren of North and West
Delhi comprised predominantly of Punjabi origin compared to children in
the South of the city (2.2%, 2.3%). When analyzed state-wise, the
highest incidence was observed in children of Punjabi origin (7.6%) and
was> 4% from several other states. Majority of the traits from
Mumbai were anemic (95.1% male and 85.6% in female). The prevalence of
anemia was lower (62.7% male and 58.4% female) children with \u3b2TT
from Delhi. This was a reflection of the higher prevalence of anemia in
children without hemoglobinopathy in Mumbai than in Delhi. Nutritional
deficiency was probably more severe and rampant in children Mumbai.
Gene frequency of Hb D was greater in schoolchildren from Delhi (1.1%)
than in Mumbai (0.7%). Hb S trait (0.2%) was observed exclusively in
children from Mumbai. A low incidence of Hb E trait (0.04%) was seen in
children in Mumbai. A higher incidence is reported from the East. The
number of cases studied from the eastern region was small as the data
from the East (Kolkata) could not be included in the analysis.
Conclusion: This study comprises a larger number of children studied
for the gene frequency of \u3b2TT and other hemoglobinopathies from
India. Population groups with higher gene frequencies require screening
programmes and facilities for antenatal diagnosis as well as increased
awareness and educational programmes to control the birth of
thalassemic homozygotes. The overall carrier frequency of \u3b2TT was
4.05% and reinforces the differential frequency of \u3b2-thalassemia
trait in schoolchildren from Delhi and Mumbai and the higher incidence
of hemoglobin D in Punjabis as reported previously. The birth incidence
calculated thereof for homozygous thalassemics would be 11,316 per year
which are added each year to the existing load of homozygous
thalassemics. This is much higher than the previously reported number
of births annually. Hence suitable control measures need to be
undertaken urgently in India