Blood transfusion remains a therapy carrying specific risks not only because of the possible blood incompatibility between the donor and the recipient; but also because of the potential transmission of blood borne pathogens. One of the ways to limit the post-transfusion adverse events is to phenotype blood donors for the main red cell blood group systems and to simultaneously detect the transfusion-transmitted infections (TTIs).
According to the WHO, in 39 countries blood donations are still not routinely tested for TTIs including HIV, HBV, HCV and syphilis; 47% of blood bags in low-income countries are examined in laboratories without quality assurance . It is estimated that 1.6 million blood units/year are deferred and destroyed due to the presence of TTI's markers .
The understanding of blood group systems has evolved to include not only blood transfusion compatibility but also the relationship between some infectious diseases and the antigens in erythrocytes . Several studies have shown an association between specific blood group antigens and the risk of pancreatic cancer [3,4,5]. Associations between the ABO system and various diseases including malaria infection, cerebral thrombosis and ovarian cancer have also been found [6,7,8].
In Gabon, few studies have been devoted to blood groups. This relative lack of information has led to undertaking this study. This investigation aimed to determine the phenotypic frequencies of the ABO and Rhesus D, C, c, E, e antigens in the Gabonese population and to study the association between transfusion-transmitted infections and the ABO blood groups.
2. MATERIALS AND METHODS
2.1. Blood donors
A retrospective analysis of blood donors' data from January to May 2015 in the national blood transfusion center (CNTS) in Libreville, Gabon was conducted. Volunteer and family/replacement donors were all apparently healthy subjects, selected after responding to a questionnaire including a medical history. They were aged 17–65 years weighing over 50 kg and eligible for blood donation. Socio-demographic characteristics were recorded, and venous blood was collected in blood collection bags following standard procedures.
2.2. Determination of ABO and Rh phenotyping
ABO and Rhesus phenotyping were obtained using monoclonal monospecific antisera: anti-A, anti-B, anti-AB, anti-D, anti-E, anti-C, anti-c, and anti-e with an automate (QWALYSⓇ 3, DIAGAST, France) or a card gel (ID Card, BIO-RAD) according to manufacturer's instructions. Positive and negative control red cells were used and the Beth-Vincent and Simonin-Michon's tests were performed as controls.
2.3. Serological analysis
Antibodies to HCV and HIV types 1 and 2 were detected using Monolisa HCV Ag-Ab ULTRA version 2 and Genscreen HIV-1/2 version 2 (BIO-RAD, Marnes-la-coquette, France). Hepatitis B surface antigen (HBsAg) and antibodies to Treponema pallidum were screened with Monolisa HBsAg ULTRA and Treponema pallidum haemagglutination test (BIO-RAD, Marnes-la-coquette, France) following the manufacturer's instructions.
3.1. ABO and Rh phenotypic frequencies
From a total of 4,744 blood donors, 59.7% were in the age group of 21-30 years with a mean age of 29.9 ± 7.0 (range 17-61 years). Of these, 83.1% donors were male and 16.9% donors were female.
Among blood donors the overall prevalence of blood groups O, A, B and AB were 58.9%; 21.0%; 17.6% and 2.6%, respectively (Table 1). The majority of blood donors from O blood group were male (48.8%). AB blood group was the least represented among blood donors (2.2% of male and 0.4% of female) (Table 1).
In the Rhesus blood group, 5 antigens were tested: D (RH1), C (RH2), E (RH3), c (RH4) and e (RH5). The absence of the D antigen was denoted d (Rhesus negative). The frequencies of Rhesus antigens D, d, C, E, c and e were respectively 97.7%; 2.3%; 15.9%; 17.6%; 99.9% and 99.3% (Table 2). The majority of Rhesus negative individuals was male (2.0%) and from O blood group (1.4%). Only 0.3% of female was Rhesus negative and 0.1% of blood donors were both AB blood group and Rhesus negative (Table 2).
The major Rh phenotypes observed among blood donors were respectively Dccee (66.5%), DccEe (15.3%) and DCcee (13.5%). The minor phenotypes obtained were DCcEe (1.5%), ddccee (1.5%), dCcee (0.8%), DccEE (0.7%), DCCee (0.1%) and DCCEe (0.02%).
3.2. Association between blood groups and
Among blood donors 233/4,744 (4.9%) were infected with at least one pathogen. The overall seroprevalence of antibodies to HIV, HCV and syphilis was 1.1%; 0.5% and 1.6%; HBsAg prevalence was 1.7%. The seroprevalence of HIV, HBV, HCV and syphilis markers was compared between blood donors of blood group O and non-O as shown in Table 3.
HIV, HCV and syphilis markers seroprevalence was similar in blood donors of group O compared to non-O blood groups (Table 3). However, the prevalence of HBsAg was twice higher among non-O blood groups donors compared to donors of O blood group [OR= 2; 95%CI: 1.3, 3.2; p = 0.003].
|Continents/countries||Frequencies of ABO and RhD (%)||References|
|Present study (N= 4,744)||58.9||21.0||17.6||2.6||97.7|
|Congo (N= 5,400)||52.3||23.1||21.1||3.5||Ref. |
|Cameroon (N= 14,546)||48.6||25.1||21.9||4.5||96.3||Ref. |
|Burkina Faso (N= 37,210)||43.4||22.7||28.2||5.8||86.2||Ref. |
|Morocco (N= 344,954)||46.1||33.9||15.7||4.3||Ref. |
|India (N = 12,701)||28.7||28.7||32.1||10.5||94.5||Ref. |
|Japon||29.9||39.8||19.9||9.9||- Ref. |
This study aimed to determine the prevalence of ABO and Rhesus blood groups among blood donors and their association with TTIs. This study shows the distribution of ABO and Rhesus phenotypes in a relatively large population of Gabonese blood donors. The phenotypic frequency of blood groups A, B, AB, O and D were respectively 21.0%, 17.6%, 2.6%, 58.9 and 97.7% (Tables 1 and 2). Group O and Rh positive blood groups were predominant in contrast with AB and Rh negative groups. The AB blood group was relatively rare, (0.4% in women and 2.2% in men). There were very few Rh negative women (0.3%) limiting the risk of maternal-fetal incompatibility and its prevention during pregnancy. The major Rhesus phenotypes observed were Dccee (66.5%), DccEe (15.3%), DCcee (13.5%). Indeed, Dccee Rhesus phenotype has been previously described as more prevalent in black populations9. The frequency of Dccee phenotype found in our study is comparable to that reported in Mali10. However, it is lower than the 73.6% reported in southern Nigeria .
The prevalence of the ABO blood groups were compared with those obtained in a previous study in Gabon, which reported the following phenotypic frequencies: 20% for A, 17.3% for B, 4.1% for AB and 58.6% for group O . These results are similar to ours presented here.
However, AB blood group prevalence was higher in the study by Languillat et al , although the difference observed was not statistically significant (X2 = 2.4, p = 0.122).
Frequencies of the ABO and Rh blood groups obtained from blood donors were compared to neighboring donor populations of Central Africa (Congo and Cameroon), West Africa (Burkina Faso), North Africa (Morocco) and the world (Table 4). The prevalence of ABO phenotypes in Gabon was significantly different from those observed in other African countries such as Congo, Cameroon, Burkina Faso, and Morocco [13,14,15,16]. In fact, the frequency of the O blood group was higher than that observed in these African countries while the prevalence of blood groups A and B was lower. Unsurprisingly, the ABO phenotypic prevalences in this study were very different from those observed in Asia, including India and Japan; in Europe and the USA [17,18,19,20]. This could be explained by the genetic distance between the predominantly Gabonese black population and population of Caucasian and Asian descent. The high prevalence of group O in sub-Saharan Africa has been in part attributed to selection related to malaria being less severe clinically in carriers of O blood group [21,22,23].
This study also evaluated the association between ABO blood groups and blood-borne infections such as HIV, HBV, HCV and syphilis. The prevalence of seroreactive HIV, HBV, HCV and syphilis markers was 1.1%, 1.7%, 0.5% and 1.6%, respectively. These seroprevalences were lower than seroreactivities reported in a previous study . No confirmation was performed so that the prevalence of antibodies to HIV, HCV and syphilis was likely considerably overestimated. The difference between the two sample sizes, the selection of Gabonese donors only in the present study and the evolution of these infections' epidemiology could partly explain these differences.
No significant association between HIV, HCV, syphilis and ABO blood groups was found among blood donors. However, the risk of HBV infection appeared twice higher among non- O donors compared to O blood group donors. This result would need to be supported by detection of HBV DNA with a sensitive assay. It is however in agreement with previous studies [25,26]. A recent study showed a higher risk of hepatocellular carcinoma associated with hepatitis B in non-O blood group compared to O blood group patients .
This study reports the prevalence of the ABO and RhD blood groups in a representative sample of the Gabonese blood donor population. It also suggests the association between the ABO blood group and chronic HBV infection.
Acknowledgments: We thank all the participants of this study, the CNTS' staff Colette Holmann Yeno, Ripaire Mboumba, Rita Alembe Mayindo, Anicet Mouity Matoumba and JPA for critically reading the manuscript.
Ethics approval: This study was approved by the CNTS Ethics Committee.
Competing interests: the authors declare no conflict of interest.
Availability of data and material: Data and material could be available on demand.
Funding: We are grateful to the National Blood Transfusion Center its financial support through le programme de support à la recherche.