Prevalence and associated risk factors of transfusion transmissible infections among blood donors at Regional Blood Transfusion Center Nakuru and Tenwek Mission Hospital, Kenya

Introduction Unsafe transfusion practices can put millions of people at risk of Transfusion Transmissible Infections (TTIs). In Kenya the current blood transfusion scheme involves screening of blood for HIV, Hepatitis B virus (HBV), Hepatitis C virus (HCV) and syphilis. Malaria is also a blood-borne disease which is not currently screened for. In Kenya blood donor selection criteria were reviewed in 2009. Regular review of effectiveness of donor selection criteria can help reduce TTIs prevalence amongst donors and thus make the blood supply safer. Methods A cross sectional study was conducted between November 2011 to January 2012 among 594 blood donors in the Regional Blood Transfusion Center Nakuru and Tenwek Mission Hospital. Socio-demographic characteristics and associated risk factors were collected using a standard blood transfusion service questionnaire. Donors were obtained through systematic sampling. Each donor sample was screened, for HIV-1 and HIV-2, HBV, HCV, syphilis and malaria parasites. Results The overall prevalence of TTIs was 14.1%, which ranged from 0.7% for malaria to 5.6% for HBsAg. Blood donors who were married (P=0.0057), had non-formal or just primary education (P=0.0262), had multiple sexual partners (P=0.0144) and in informal occupation (P=0.0176) were at higher risk of HIV positivity. History of blood transfusion/blood products (P=0.0055), being married (P=0.0053) were high risk factors associated with positive syphilis. Being male (P=0.0479) was a high risk factor to HBV infection. Conclusion The prevalence of TTIs indicates a need to review the questionnaire and apply it strictly for donor selection. The 0.7% prevalence of malaria, poses a serious health risk to non-immune recipients of transfusion. Malaria should be included among mandatory TTI tests in Kenya.


Introduction
Although timely transfusion saves millions of human lives worldwide each year, unsafe transfusion practices can put millions of people at risk of Transfusion Transmissible Infections (TTIs) [1]. Evaluation of data on the TTIs which include among others; HIV, HBV, HCV, syphilis and malaria, in blood and blood component donors, permits an assessment of the occurrence of infections in the blood donor population and consequently the safety of the donations [2]. It also gives an idea of the epidemiology of these diseases in the community [3]. Transfusion associated infections continue to be a big threat globally [2]. The TTIs can exist asymptomatically in donors, so donors must be screened for high-risk behavior related diseases. In Africa 5-10% of HIV transmission is as a result of contaminated blood transfusions [4]. Infection by HBV and HCV causes serious mortality, morbidity and financial burden thus it is a major global health problem [5]. In Sub-Saharan Africa, 12.5% of patients who receive blood transfusion are at risk of post-transfusion hepatitis [6]. Syphilis is less readily transmitted by blood and the prevalence is low in most studies reported [2]. In Africa a child dies every 45 seconds of malaria, the disease accounts for 20% of all childhood deaths [3].
Studies conducted in Benin revealed that there is a presence of plasmodium falciparum in 30.2 and 33.5% of blood donors respectively [7].
Kenya's need for blood is estimated at between 200,000 and 250,000 units per year. However, with the WHO guidelines estimate of 10-20 units per 1,000 people then the need in Kenya can be estimated at between 380,000-760,000 units annually. Currently, 125,000 units of blood are collected through the National Blood Transfusion Service (NBTS). The deficit is thought to be covered by Family Replacement Donors (FRD) [8]. The FRD account for up to 35 percent of donors in Kenya, despite them being more risky [8]. In this study blood donors were either Volunteer Non-Remunerated Donors (VNRD) or FRD.
Nakuru Regional Blood Transfusion Center (RBTC) recruited VNRD from low-risk populations, while in Tenwek Mission Hospital donors were relatives or friends of patients to replace blood used. A standard questionnaire was administered to all consenting donors from the two facilities. Regular review of effectiveness of donor selection criteria can help reduce TTIs prevalence amongst donors and thus make the blood supply safer. Kenya is one of the countries with high prevalence of HIV, HBV, HCV and other blood-borne infections. The population prevalence with HIV (6.0%), HBsAg (8.0%), ant-HCV (2.0%) and syphilis (0.5%) [9]; therefore there is little published data on prevalence of TTIs, socio-demographic characteristics & associated risk factors among blood donors in Kenya.
In Kenya, the current blood transfusion policy recommends screening of blood for HIV, Hepatitis B, Hepatitis C and syphilis. Malaria is also a blood-borne disease which is not screened for. This study included testing for malaria parasites which is not done routinely within the National Blood Transfusion Service (NBTS). While the search for effective therapies and vaccines continues, prevention and control of these blood-borne infections should be the goals of sustained public health efforts. The first step in ensuring blood safety is the selection of low risk blood donors. The NBTS questionnaire was introduced in 2009. The donor selection criterion has not been reviewed since then.
Donor selection criteria should be reviewed periodically as disease epidemiology changes [3]. Since introduction, the validity of the questionnaire has not yet been tested. This study will give NBTS very useful information on the strength of the questionnaire in eliminating high risk donors. Many TTIs including HIV and hepatitis have an infectious latent phase when carriers are seemingly healthy. In malaria endemic regions, healthy persons may have low grade parasitaemia that can cause death in non-immune persons. These latency stages pose major challenges to Blood Transfusion Services across the world as they seek to minimize collection of blood from infected persons through appropriate donor selection. To increase the efficacy of donor screening and selection, it is important to understand the risk factors for these infections in different populations [10]. Several studies within Africa, suggest that the African blood donor is mostly young [7], with a mean age of 28.9±8.5 years. This is also the population at highest risk of acquiring HIV and malaria infections. There is need to ensure that the blood the recipients receive is safe from known infections. This study therefore seeks to determine the prevalence, socio-demographic profiles and examine associated risk factors of blood donors at RBTC Nakuru and Tenwek Mission Hospital. The findings will guide in targeting low risk donors and donor selection practices within the Kenya NBTS with the aim of ensuring a safer blood supply in Kenya.

Methods
Study design, setting and eligibility: this was a cross sectional study, whereby data on demographic characteristics and associated risk factors of TTIs was obtained from blood donors at two health facilities. Whereas RBTC Nakuru collects blood from VNRD, Tenwek uses FRD and does not subject them to the standard questionnaire.
The inclusion criteria of the study population included: age 16 years and 65 years, body weight greater than 50kg, haemoglobin level greater than 12.5 g/dl and informed consent to participate in the study whereby the exclusion criteria were: age less than 16 years or more than 65 years, body weight less than 50kg. haemoglobin values less than 12.5 g/dl, history of jaundice, sickle cell disease, hypertension or current fever, recent illness or transfusion, high risk sexual behavior and lack of consent.
Sampling method: systematic sampling method was conducted between November 2011 and January 2012 among blood donors in the two facilities, who met the facilities criteria for donation. A Sampling frame was created using the blood donor register. The number of blood donations at the two facilities was an average of 1,600 in Nakuru and 120 in Tenwek per month. Due to small workload in Tenwek a proportional allotment was not plausible. An intuitive assignment to Tenwek a sample size of 100 and to Nakuru a sample size of 594-100=494 was done. A random starting point was selected after which every k th person in the population list was selected. The sampling interval was calculated as follows: K=N/n, Where N was the population size and n was the sample size. k=3 in Nakuru and 1 in Tenwek. Using this procedure each person in the population had a known and equal probability of selection.
Data collection: data, including socio-demographic characteristics such as age, sex, marital status, occupation, residence, level of education and selected risk factors which include history of jaundice, sickle cell disease, hypertension or current fever, recent illness or transfusion, high risk sexual behavior were collected from consenting participants using standard blood transfusion service questionnaire. Participants confidentiality was ensured by coding and omitting information that identifies the participants. Privacy was maintained during interviews.

Results
A total of 594 participants were enrolled in the study of which 17% (100) were FRD from Tenwek Mission Hospital and 83% (494) were VNRD from RBTC Nakuru. Of the 594 participants, males constituted 72%. The overall ages of the donors ranged from 16-62 years, median age 20.0 years, RBTC donors had a median age of 19 years, while donors from Tenwek mission hospital had a median age of 25.5 years. Overall 75% of all donors were single, (82% in Nakuru and 40% in Tenwek) ( Table 1). The TTIs were more common in males, with HBsAg having the highest prevalence of 6.8%. In Tenwek 22.2% of donors with HBV infection were in age group 36-40 years. HIV sero-prevalence was highest among those with primary as their highest level of education (14.7%) ( Table 2). Of the 594 blood donors, the overall prevalence of TTIs was 14.1%. Although Tenwek represented 17% of the sample size, 25% of those with TTIs were from this facility. Individual TTIs were most common among the FRD in Tenwek with a prevalence of 9.0%, 6.0%, 8.0%, 2.0% and 0% of the subjects positive with HIV, HBsAg, ant-HCV, syphilis and malaria.
Only four donors had malaria and all of them were from Nakuru ( Figure 1).
Potential factors associated with various TTI statuses among blood donors in the two sites were analyzed. On bivariate analysis, three socio-demographic high risk factors were found to be significantly associated with positive HIV status. Age above 30 years (P-value=0.003), being married (P-value=0.0007), having informal occupation (P-value=0.05), not educated beyond primary level (P-value=0.005) and having multiple sexual activity (P-value=0.02). Low risk factors significantly associated with HIV positive status were: age below 20 years (P-value=0.02), being single (P-value=0.0001) and being a student (P-value=0.02) ( Table 3). Being married (P-value=0.009) was a high risk factor significantly associated with syphilis positive status, while being single (P-value=0.01) was a low risk factor among blood donors ( Table 4). None of the factors were significantly associated with positive HCV infection.
All factors that were significant at p≤0.1 on bivariate analysis were subjected to the unconditional logistic regression model using backward stepwise elimination method. The final "best-fit" model contained five factors that were independently associated with positive HIV status: donors who were married (aOR=4.56; P-value=0.0057), having non-formal or just primary education (aOR=9.05; P-value=0.0262), informal occupation (aOR=4.08; P-value=0.0176) and multiple sexual partners (aOR= 189.78; P-value=0.0144). History of previous blood transfusion/blood products (aOR=9727.90; P-value=0.0055) and being married (aOR=12.27; P-value=0.0053) were high risk factors associated with positive syphilis.

Discussion
This study revealed that, the majority of blood donors were young males 72%. This may be attributed to deferral of potential female donors due to anaemia, pregnancy, breastfeeding or childbirth which are all criteria for donor exclusion. In this study the ratio of male to female blood donors is similar to other studies [3] and found male: female ratio was 5:1. In the Kenyan survey [9], more men compared to women donated to a blood transfusion service among voluntary and FRDs. A difference in occupation and marital status was noted between the two facilities, whereby in Tenwek Mission Hospital, most donors 60% had informal occupation and 60% were married, while in RBTC Nakuru 70% were students and 82% singles were the predominant group. This is biased by higher predominance of students especially among voluntary donors; most of the recruitments were from secondary school students. These results are in line with those reported by Cunha and his collaborators in Mozambique, who noted that the proportion of volunteer donors (69%) who completed secondary school education was higher than the familial ones [7].
This contrasts with findings from Burkina Faso, which found that more than 31% of their donor population is illiterate or received only primary school education [7].
Overall majority of the participants were aged between 16-20 years with a median age of 20.0 years. Routinely, RBTC targets donors of a younger age, mostly high school and college students, as this group are perceived to be more willing to donate blood and also a low risk group. These findings are similar with a study in Kenya where 59% of voluntary donors were <25 years old [11]. In a review of blood donors in Africa, it was observed that, African blood donors are mostly young. In Kenya, a mean age of 28.9±8.5 years was reported among blood donors; in Burkina Faso, reported a mean age of 28±7.9 years, In Rwanda more than 75% are less than 30 years [7]. These mean ages are 10-15 years less than those observed in European countries.
This difference may be explained by the fact that the voluntary donor programmes in Africa tend to be centered on secondary school and university students and (Donor ages tend to relate to the donor type), where the median ages for secondary school, public blood drive and family replacement donors were 18, 25 and 32 years, respectively [7].
The overall prevalence of HIV was more in male than female, this is similar to what was reported in Osogbo, south-west Nigeria [12] in which more male (82%), were infected by HIV than females (18%).
The prevalence of HIV in RBTC Nakuru was higher in females 3.1%  [7]. The sub-Saharan region is highly endemic with HBsAg carrier rates of 9-20%, whereas 56-98% of the adult population shows evidence of past exposure to HBV infection [7]. Studies in Kenya showed an HBsAg carrier rate of 5-30% [18]. The first peak of HBV infection in Kenya appears to be at early school age, whereas the second peak occurs at puberty and childbearing age [18]. This finding is similar with a previous report in which higher prevalence of HBsAg was observed among the youths in the age groups of 26-36 years and 36-45 years compared to age group of greater than 45 years [6].
In HIV positive donors, the highest infection occurred in the age group 36-40 years and above 40 years of age. The possible reason could be these are age groups which are sexually active and married.
It has been shown in this study that being married is significantly associated with positive HIV status (P-value=0.0057). These findings are partly in line with previous results where the most affected were the youth of age group 18-47 years [3,11]. In this study TTIs are common and a major concern among the blood donors with an overall prevalence of 14.1%. Tenwek Mission Hospital with mainly FRD had the highest prevalence of TTIs (25%), in contrast to 11.9% in Nakuru VNRD, though this difference was statistically not significant. The prevalence difference between the two sites is comparable to other studies. In Kenya on comparison of voluntary and FRD on a population based survey, it was found that there is a prevalence of 7.4% and 2.6% respectively [11]. In Eritrea, the total blood donors positive for serological markers for TTIs was 3.8%, of these, voluntary blood donor positive for TTI markers was 3.5% and 5.1% for FRDs [4]. The high prevalence of TTIs in Tenwek Mission Hospital could be attributed to the fact that most of the times, relatives or friends of the family are brought in to cater for their relatives blood needs. As evidenced by the findings of this study, FRDs present a greater risk than VNRDs. The low prevalence of TTIs in VNRDs in this study could be attributed to the fact that voluntary donors are recruited from low-risk populations, coupled with well-trained blood donor staffs at the RBTC who practice effective donor education, stringent donor selection, and no pressure associated with selfdeferral as is likely to happen with FRDs. This blood donor recruitment strategy is advocated for by the World Health Organization to improve overall blood safety [19].
In this study the prevalence of all the individual TTIs markers, except malaria was higher among the FRDs than VNRD. This difference was statistically significant for HIV (P=0.0025) and HCV (P=0.0051). It is conceivable that a person in need of money is more likely to conceal  [22].
However these findings are lower than the prevalence of HBsAg 18.6, ant-HCV 6.0% but differ with regards to HIV (3.1%) for which higher prevalence was observed in the current study, but similar (1.1%) with syphilis in the study done in Osogbo, south-west Nigeria [12].
Overall, the commonest TTI was HBsAg with 5.6% positivity rate. The possible reason for the high rate of HBV is a high prevalence in the general population arising from high infectivity potential of the virus, low immunization status and bloodletting exercises to treat different diseases [22]. This data is similar with earlier reports that Kenya is a high endemicity area for HBV [18]. Studies in Kenya showed HBsAg carrier rates of 5-30% [18]. Hepatitis B virus therefore is highly contagious and relatively easy to be transmitted from one infected individual to another. This is because HBV virus is present in all body fluids and secretions, including blood, saliva, semen, sweat, breast milk, tears and urine, and therefore, virus is transmitted through various routes, apparently depending on the incidence of the disease in the region [18]. Previous study has reported that prevalence of an infection among the donors reflects the disease burden in the society [23]. This figure (5.6%) prevalence of HBsAg in the current study is higher than 4% in Kenyan donors [24], 4.3% in Egyptian donors [25]. It is lower than 14% among blood donors in Zimbabwe, southern Africa [13]. In this study 1.2% of study participants had Treponema Pallidum. The reasons for the relatively lower rate of sero-prevalence, is conceivable that syphilis is less often transmitted by blood. The prevalence is low in most studies reported [5], 1.2% of syphilis among Kenyan donors [24], 1.2% found in northern-eastern, Nigeria [15]. However it is lower than 3.96% reported in Burkina Faso [26], but is higher than 0.05% among donors in south India.
The low prevalence of syphilis in this study might be through increased awareness of the disease and prompt treatment which is cheap and effective. Antenatal screening and treatment for syphilis might also have contributed to low prevalence of syphilis.
There is scant information on malaria among blood donors. Malaria screening test has not been incorporated as one of the routine tests in NBTS panel of testing. In this study a prevalence of malaria of 0.7% was found. This study was conducted in a low-malaria prevalence region which gets malaria only in the rainy seasons from April to October (non-endemic region). This can be anticipated that, during the high season the prevalence can be higher. This is almost in accordance with previous study [27]

Conclusion
The prevalence of TTIs identified among apparently healthy blood donors is significant and a public health problem.  Tables and figure   Table 1: socio-demographic characteristics of blood donors in the Regional Blood Transfusion Center Nakuru and Tenwek Mission Hospital