Blood Groups and their Ethnic Distribution in a Teaching Hospital of Kathmandu , Nepal

Introduction: ABO and Rh blood group systems are the most important blood grouping systems from clinical aspect. Determination of blood group is important for blood transfusion therapy, medico-legal purposes, organ transplantation, settlement of paternity disputes etc. Methods: A cross-sectional descriptive study was carried out for a period of one year from 1st January 2011 to 31st December 2011 in blood bank of Tribhuvan University Teaching Hospital. All blood samples collected for blood group determination were included in the study. Blood group was determined by slide agglutination method using commercial antisera. Results: A total of 13568 blood samples were analyzed, 5123 (37.75%) were male and 8445 (62.25%) were female. Frequencies of blood groups A, B, AB and O were found to be 4034 (29.7%), 3665 (27.0%), 1114 (8.2%) and 4755 (35.1%). Frequencies of Rh positive and Rh negative blood groups were found to be 13200 (97.3%) and 368 (2.7%). Blood group O was common in Brahmin, Chhetri, Tamang, Lama, Gurung, Sherpa, Terai Brahmin, Muslim and Yadav ethnicities; blood group A was common in Newar, Rai, Magar, Limbu and Sanyasi ethnicitites; and blood group B was common in Tharu and Marwari ethnicities. Conclusions: Blood group O was found to be the most common blood group while AB was the rarest one. It was found that blood group O is the more common in Sherpa, Brahmin and Yadav; A in Limbu, Rai and Newar; and B in Tharu and Marwari ethnicities. _______________________________________________________________________________________


INTRODUCTION
Human blood can be divided into different groups according to the presence or absence of antigens on the red blood cell membrane.There are at least 30 commonly occurring and hundreds of other rare antigens on the red blood cell membrane. 1The International Society for Blood Transfusion (ISBT) Working Committee 2 catalogue currently lists antigens under 33 different blood grouping systems.ABO and Rh blood grouping systems are the most important ones clinically.
The most important clinical aspect of blood groups remains to be blood transfusion therapy.Antigens of these two blood grouping systems are the most commonly involved ones in transfusion reactions.Other applied aspects of blood grouping systems are medico-legal use, organ transplantation, assistance in settlement of paternity disputes, association with certain disease etc. and ethnic distribution of ABO and Rh blood group in a teaching hospital.

METHODS
Cross-sectional descriptive study was conducted in Blood Bank of Tribhuvan University Teaching Hospital from 1 st January, 2011 to 31 st December, 2011 after obtaining ethical approval from Institutional Review Board (IRB).All blood samples collected for blood group determination during this one year period were included in the study after obtaining consent.Foreign nationals were excluded from the study.ABO and Rh blood groups were determined by slide agglutination method using commercial blood grouping reagents.Data analysis was done with IBM SPSS Statistics version 20.

RESULTS
During the one year period of study, 13568 blood samples were received for blood group determination.Out of 13568 subjects, 5123 (37.75%) are male and 8445 (62.25%) are female.The most common blood group was O positive 4624 (34.1%) while, AB negative 27 (0.2%) blood group is the rarest one (Figure 3).The frequencies of blood groups A, B, AB and O are found to be 4034 (29.7%), 3665 (27.0%), 1114 (8.2%) and 4755 (35.1%) respectively (Figure 1).The frequencies of Rh positive and Rh negative blood groups are found to be 13200 (97.3%) and 368 (2.7%) respectively (Figure 2).A study on 2093 Jirels, a small Kirat tribe of Nepal showed blood group A to be the most prevalent one (55%) while blood group O to be the least prevalent one (8%) among Jirels. 7e frequency of ABO blood groups are reported as blood group O 44-45%, blood group A 41-42%, blood group B 10% and blood group AB 4% in European and American people. 1,8,9Study by Garratty G et al reported blood group O (46.6%) as the most frequent blood group amongst Americans, followed by A (37.1%), B (12.2%) and AB (4.1%). 10Although blood group O is the commonest of the blood groups in our study, the frequency of blood group B is much higher than that reported in European and American population.

Table 1 )
4 Singh R reported blood group O as the most common one amongst Brahmin and Gurung ethnicities; blood group A amongst Newar, Chhetri and Tamang ethnicities; and blood group B among Sherpa ethnicity.5PramanikTandAdhikariP found blood group O predominantly among Brahmin, Magar and Gurung ethnicities; blood group A among Chhetri and Newar ethnicities; and blood group B among Sherpa and Lama ethnicities.4CONCLUSIONSInour study, blood group O was the most common blood group amongst ABO blood groups, followed by blood group A, blood group B and blood group AB.Blood group O was the commonest blood group in Brahmin, Chhetri, Tamang, Lama, Gurung, Sherpa, Terai Brahmin, Muslim and Yadav ethnicities; blood group A was the commonest blood group in Newar, Magar, Limbu and Sanyasi ethnicities; and blood group B was the commonest blood group in Tharu and Marwari ethnicities.