Prevalence of p24 antigen among a cohort of HIV antibody negative blood donors in Sokoto, North Western Nigeria - the question of safety of blood transfusion in Nigeria

Introduction Blood transfusions remain a substantial source of HIV in SSA particularly among children and pregnant women. Aims and objectives: This aim of this retrospective study was to investigate the prevalence of p24 antigen among HIV antibody seronegative blood donors in Sokoto, North West Nigeria. Methods A total of 15,061 HIV antibody negative blood donors with mean age and age range (29.2 ± 8.18 and 18-50 years) were screened for p24 antigen between January 2010 to July 2013 using the Diapro Diagnostic immunoassay kit for P24 antigen (King Hawk Pharmaceuticals Beijing China). Results The overall prevalence of p24 antigen among the HIV antibody negative donors sample was 5.84%. The yearly prevalence was 9.79, 8.12, 2.7 and 2.84% respectively in 2010, 2011, 2012 and 2013. Of the total number of blood donor tested, 14,968 (99.38%) were males while 93 (0.62%) were females. The prevalence of P24 antigen was significantly higher among male blood donors 873 (5.8%) compared to females 7(0.05%), (p= 0.001). P24 positivity was significantly higher among blood group O blood donors compared to A, B and AB donors (494 (3.29%) compared to 184 (1.89%), 196 (1.30%) and 6 (0.04%)) respectively, p = 0.001). The prevalence of P24 antigen was significantly higher among Rhesus positive blood donors compared to Rhesus negative (807 (5.36%) versus 73 (0.48%), p =0.001). Conclusion Blood transfusion in Nigeria is associated with increased risk of HIV transmission. There is the urgent need to optimize the screening of blood donors in Nigeria by the inclusion of p24 antigen testing into the blood donor screening menu. The Nigerian government urgently need to adopt the WHO blood safety strategies to reduce the risk of transmission of HIV through blood transfusion.


Introduction
The World Health Organization has estimated that there were 40 million people were infected with human immunodeficiency virus (HIV) globally at the end of 2001, and the majority of them were in developing countries [1]. The countries affected the most are economically poor and therefore unable to afford expensive diagnostic and monitoring tests. Blood transfusion is an essential part of modern medical care. Inadequate and unsafe blood supply causes avoidable deaths and transmits infectious diseases, including HIV. Transfusion of blood infected with HIV is one of the most effective modes of transmission of the virus. The risk of acquiring HIV infection following transfusion with HIV-positive blood has been estimated to be as high particularly in sub Saharan Africa (SSA). The use of HIV antibody -based test for the screening of blood donor is sub optimal. Evidenced-based data and best practices from the developed world indicates that implementing evidenced based national testing and donor selection algorithm that establishes the use of tests capable of detecting donation in the window phase of HIV infection (P24 and NAT) is the only way forward to reducing the potential of transmitting HIV infection through blood transfusion [2].
The HIV antibody test offers the advantages of simplicity and cost effectiveness for verifying infection, but it is less than perfect because of the possibility of transfusing antibody negative unit from a donor in the window phase of HIV infection. Newer technologies exist that can contribute to an accurate diagnosis, assist in monitoring the response to therapy, and can be used to effectively predict disease outcome. Viral isolation through viral culture, nucleic acid tests to detect viral RNA, and tests to detect p24 antigen can be used to demonstrate virus or viral components in blood, thereby verifying infection and potentially reducing the risk of transfusion of blood in the window phase of HIV infection. The p24 antigen assay measures the viral capsid (core) p24 protein in blood that is detectable earlier than HIV antibody during acute infection. It occurs early after infection due to the initial burst of virus replication and is associated with high levels of viremia during which the individual is highly infectious but may be antibody negative [2].
There is high rates of HIV in SSA countries and this continue to present a substantial challenge for blood services in recruiting and retaining safe blood donors. In sub-Saharan Africa, transfusiontransmitted human immunodeficiency virus (HIV) infection persists, particularly among women with pregnancy and haemorrhagerelated anaemia and children with malaria -related anaemia who are the major recipient of blood transfusions [3]. Nigeria. Evidence-based data generated will help in the formulation of policy to improve the safety of blood and blood product as well as optimize the quality of blood transfusion service delivery in Nigeria.

Study participants
This present retrospective study included a total of 15,061 blood donors who were screened at the blood transfusion unit of the

Study area
This present research work was carried out at the Haematology and

Statistics
Statistical analyses were conducted using SPSS (version 11) software. Comparisons between populations were made using the Student´s t-test for parametric data and the Mann-Whitney test for non-parametric data. An alpha value of <0.05 denoted a statistically significant difference. Correlation was compared using a version of linear regression analysis.

Results
A total of 15,061 blood donors were screened for HIV from January 2010 to July 2013 ( Table 1)

Discussion
Compared to most developed countries of the world, the risk of human immunodeficiency virus (HIV) transmission by transfusion of blood and blood products is extraordinarily high in SSA. High level of blood safety in developed countries has been accomplished by successive refinement in donor screening and testing procedures for the detection and inactivation of different infectious agents in blood and blood products. The introduction of P24 antigen testing and NATs in European blood centres has improved output to detect donations from individuals in the very early stages (window phase) of infection [8,9]. In most settings in Nigeria, donor screening for HIV is still entirely antibody based. In this present study we observed that 5.84% of donors certified HIV negative by antibody based test were positive for p24 antigen. The p24 antigen test has become an important test in determining the presence of viral antigen in individuals declared seronegative by an antibody-based test [10]. Our finding is in agreement with previous report in the United States of America which indicated that testing for HIV p24 antigen can potentially shorten the seronegative window to less than 20 days [11]. The detection rate of donors who are positive for p24 antigen but negative by antibody-based test was observed to be several cases per year among 12 million annual blood donations.
Similarly observation from Argentina, a country where blood donor HIV antibody detection has been mandatory and p24 antigen screening is recommended, indicates that out of a total of 30,132 consecutive donations screened for HIV, a total, 0.3623% of samples were repeatedly reactive. Only one donor who tested nonreactive for HIV Ab, was repeatedly reactive for p24 Ag [12]. Our finding is at variance with previous report in Saudi Arabia which tested 24,654 blood donors but failed to detect a single p24 positive case [13]. The reasons for this observation may be due to the fact that the prevalence of HIV among people in Saudi Arabia is significantly low compared to Nigeria where the prevalence is high. There seems a disparity between developed countries that rely on high-performance technology to guarantee safe supplies of donated blood and resource-poor countries particularly in SSA facing many obstacles to safe blood provision. Namely those obstacles include countries, but require sophisticated technology and dedicated, welltrained personnel [31][32][33]. NAT costs 3 to 10 times more than ELISA. There is need for low-resource countries to carefully weigh the advantages and costs of using NAT. However a previous study to estimate the number of window period infections entering the Kenyan blood supply investigated over 12,000 antibody and p24 negative specimens from six national collection centres for HIV using NAT. NAT retesting found no additional HIV infections, indicating that HIV antibody and p24 antigen screening can significantly reduce HIV in the nation´s blood supply, even in a setting with a generalized HIV epidemic [16].

Secondly blood donation in Saudi
We compared the prevalence of p24 positivity based on the gender of the blood donors. P24 positivity was significantly higher among male blood donors compared to females. Our finding is at variance with previous reports in Nigeria which found the prevalence of HIV higher among females compared to males [34,35]. The small population of females among the donor population studied may also have influenced this finding.
We compared the prevalence of p24 positivity based on the ABO and the Rhesus D blood groups of blood donors. P24 positivity was higher among group O and Rhesus positive blood donors compared to non-O donors and Rhesus negative blood donors. Certain diseases have been associated with certain ABO blood groups. Our finding is consistent with a previous reports in India which observed that HIV infection was more common among adults and paediatrics who are blood group O Rh positive [36,37]. Similarly studies carried out in Enugu by Nneli and colleagues [38] and in Adamawa State by Abdulazeez and colleagues [39] indicated that HIV positivity was more predominant among group O subjects. Similarly, a study to investigate the distribution of ABO and Rhesus blood group types in 984 randomly selected human T lymphotropic virus-1(HTLV-1)infected blood donors observed that donors who are AB+ have increased risk of HTLV-1 infection [40]. The reason for this predisposition may be genetic or it may also be due to the fact that blood group O is the most prevalent ABO blood groups among blacks and Caucasians.

Conclusion
The Nigerian government must urgently adopt WHO blood safety strategies for resource-limited settings. There is the need to optimize the donor selection and testing algorithm. HIV screening of donors must become based on a combination of antibody-based test and p24 antigen test coupled with a stringent blood donor selection algorithm. Previous report indicates that except for adding HIV-p24 screening, adding other tests such as nucleic acid amplification testing (NAT) to HIV-antibody screening displayed incremental costeffectiveness ratios greater than the WHO/World Bank specified threshold for cost-effectiveness particularly for developing countries [40].

Competing interests
The authors declare that there are no competing interest associated with this manuscript.

Authors' contributions
Erhabor Osaro and Isaac Zama designed and wrote the report, Abdulrahaman Yakubu , Ikhuenbor Dorcas and Ibrahim Kwaifa designed and carried out the laboratory analysis, Aghedo Festus, Ibrahim Sani and Ndakotsu Mohammed did the statistical analysis.
All authors read and approved the final version of the manuscript. Table 1: yearly positive P24 Antigen screened blood Table 2: positive P24 Antigen screened blood among gender.