Safety of Blood Maintained in Zimbabwe: Low Transfusion Transmissible Infections among Blood Donors

Background: Low level of transfusion transmissible infections (TTIs) is an indicator of a well-performing blood donor program. Aim: The study was designed to estimate the prevalence of TTIs and to evaluate the demographic characteristics of reactive and non-reactive blood donors in Zimbabwe in 2018. Methods: A cross-sectional study was conducted using routinely available data from January to December 2018 in five branches of National Blood Service Zimbabwe (NBSZ). After initial screening for high-risk behavior with a questionnaire, weight, blood pressure and hemoglobin level, eligible donors were invited for blood donation. The following laboratory tests for TTIs were done: antibodies and antigen tests for human immunodeficiency virus 1 and 2 (HIV 1/2), tests for the surface antigen of hepatitis B virus (HBV), testing for hepatitis C virus (HCV) antibody and antibodies for treponema pallidum. Information on age, gender, NBSZ branch, marital status, occupation, donor type (first time/repeat) and help to maintain satisfactory blood safety in Zimbabwe.


Introduction
All blood donations should be screened for transfusion transmissible infections (TTIs) to ensure that blood products meet the set safety standards [1]. The TTIs include human immunodeficiency virus 1 and 2 (HIV-1/2), hepatitis B virus (HBV), hepatitis C virus (HCV), and syphilis antibodies (Treponema pallidum) [2]. All blood units which test positive (reactive) for any of the disease markers are discarded in accordance with bio-safety protocols. Data from low-income countries show that the average prevalence of TTIs was 6.71% in 2016 [3].
Transfusion of infected blood is the cause of 5% -10% of HIV infection in Sub-Saharan Africa, and 12.5% of patients who receive blood transfusions are at risk of post-transfusion hepatitis [4]. Blood donation programs face challenges in settings with a high HIV and HBV burden, such as Zimbabwe where it was estimated that 14% of persons in the reproductive age group are HIV-infected [5] and 10% adults are carriers of HBV [6].
Since the 1950s, the National Blood Service Zimbabwe (NBSZ) has fulfilled its obligation to provide safe blood and adopted the World Health Organization (WHO) recommendation of 100% voluntary non-remunerated donations [6].
Prospective donors are assessed using a questionnaire for high risk behavior, weight measurement and hemoglobin level. For the past decade, an average of 1.6% TTIs prevalence has been recorded among blood donors [4], but there are limited NBSZ published work aimed at 1) describing the demographic profile of blood donors, 2) estimating the prevalence of TTIs (HIV, HBV, HCV, and syphilis) and 3) assessing factors associated with TTIs. Assessment of the prevalence of TTIs among blood donors permits monitoring of the occurrence of the TTIs in individual blood donor sub-populations and consequently, the safety of the collected donations. It also gives an idea of the epidemiology of the TTIs among blood donors and informs decision making and policy formulation in the blood donor program.

Study Design
A cross-sectional analytical study using routinely collected data was undertaken.

National Blood Service Zimbabwe
NBSZ, a not-for-profit organization, has five branches that are situated in Ha-D. Zezai et al. Journal of Biosciences and Medicines rare, Bulawayo, Mutare, Gweru, and Masvingo. In the past decade, an annual average of 65,687 whole blood units has been collected annually. NBSZ has a standardised donor enrolment and screening procedure which defers donors with high risk behaviors such as: exchanging money, drugs, goods or favours in return for sex, history of accidental exposure to blood or body fluids in the past six months, having been a victim of sexual abuse and having unprotected sex.

Screening of Blood Donors
After receiving a pre-donation counselling, eligible blood donors' history is assessed for high-risk behaviors using a self-administered questionnaire and medical checks are done on weight, blood pressure and haemoglobin level.
Based on the assessment, those with high-risk behaviors followed by haemoglobin of <12.5 g/dl for both males and females, blood pressure outside the acceptable range (<100/60 mmHg and >180/100 mmHg) and weight < 50 kg are de-

Study Population
Individuals with weight more than 50 kgs and aged between 16 and 65 years in the blood donor program in the five branches of the NBSZ from January to December 2018 were included.

Data Variables, and Extraction
Information on age, gender, NBSZ branch, marital status, occupation, donor type (first time/repeat) and TTI test results were extracted from the NBSZ electronic database into an excel spreadsheet.

Sample Size Estimation
The sample size for this study was calculated using a formula for sample size de-Journal of Biosciences and Medicines termination for cross-sectional studies [7], with a Z-score (normal standard deviation) of 1.96 at 95% confidence, an average TTIs prevalence among blood donors in developing countries of 1.6% [6], and an absolute precision of 0.05. A minimum sample size of 2419 samples was required. However, a final sample size of 1586 was considered for the study due to logistical constraints. A simple random sampling of the blood collection forms was then conducted [8] at the five NBSZ branches to proportionally select the total sample size of 1586 for the study.

Data Analysis and Statistics
Data analysis was done in STATA 13.0 TM (Stata Corp LLC, TX, USA). Sociodemographic characteristics of blood donors were summarized as proportions.
The prevalence of TTIs was expressed as proportions with 95% confidence intervals using binomial exact test. Socio-demographic factors associated with TTIs were assessed using chi squared test. Level of significance was set at 5%.

Ethics Approval
The study protocol was approved by NBSZ (

Results
Of the total 1586 blood donors, 972 (61.3%) were males and the mean (standard The prevalence estimates are shown in Table 2. Thirteen donors (0.81%) had at least one TTI; five (0.32%) were reactive for HIV 1/2, seven (0.44%) for HBV and one (0.06%) for Treponema pallidum antibodies. There were no individuals with a co-infection. There were also no donors reactive for HCV, and therefore, no entry was recorded for HCV seropositive results.
Factors associated with TTIs are described in Table 3. The prevalence of TTIs was higher in 31 -45 years age-group compared to 16 -30 years age group (2.3% vs 0.53%; p = 0.014). First-time donors had a higher TTI prevalence compared to repeat donors (4.74% vs 0.15%; p < 0.001). The other analyzed variables did not show any statistically significant associations with seropositivity for any of the analyzed TTI markers (p > 0.05).

Discussion
In our study, the overall prevalence of TTI was low, with the HBV prevalence being the highest followed by HIV prevalence. The findings were consistent with previous studies [9]. There has been a steady decrease in the overall prevalence of TTI from ~4% in 2010 to <1% in the present study and this decrease has been recorded for all the TTI in Zimbabwe [9]. Similar declining trends in prevalence have been reported in sub-Saharan Africa [10].  [12]. Furthermore, the specific decline in Zimbabwe can also be attributed to improved donor screening through the internally improved blood donor risk and inventory model. However, continued commitment and funding are required to further reduce the prevalence.
The TTI prevalence among first-time donors was ~5% compared to the prevalence of 0.15% among repeat donors. This illustrated that repeat blood donors were the safer source of blood in Zimbabwe during the study period. A study in Zambia also confirmed similar findings [1]. Though the donor screening has improved still some blood units are discarded posing a cost and safety implication. Stricter mechanisms of donor screening are required. In addition, strategies to reduce the prevalence of HIV, HBV, and syphilis in the general population will also reduce the TTI prevalence in first-time donors.
In our study, only 15% were first-time donors, this is lower than what has been reported in most African countries [12]. This calls for recruitment strategies to increase the first-time donors and eventually, the entire pool. The results reflected a well-performing blood donor program which relies on retaining repeat donors.
We did not find HCV and co-infections among donors. Though this was encouraging, it could be due to two key reasons; first, the small study sample size, second; HCV transmission is most frequent in high-risk populations including people who inject drugs and men who have sex with men. These population groups are low in Zimbabwe [13].
The strengths of the study were that it used routinely available data which was kept in a central electronic database and the sample was fairly representative of a nation-wide donor population. Additional studies on this area can be further routinely be undertaken by NBSZ to obtain updated trends in the TTI prevalence and identify emerging risk factors.

Conclusion
This study has shown a low TTI prevalence in Zimbabwe with an evident higher prevalence of HBV. Blood safety is being maintained in Zimbabwe. We recommend continued close monitoring of the most risk sub-populations, and adoption of new TTI testing technologies.

Limitation
The study could not assess the odds ratios and/or risk ratios as we did not have a sufficient number of persons with TTIs. Information on occupation and marital status was missing in one third of the records.