High prevalence and poor linkage to care of transfusion‐transmitted infections among blood donors in Dar‐es‐Salaam, Tanzania

Summary Blood transfusion is one of the most commonly relied upon therapies in sub‐Saharan Africa. Existing safeguards recommended include systematic screening for transfusion‐transmitted infections and restricted voluntary nonremunerated blood donor selection. We report the transfusion‐transmitted infection screening and notification practice at a large urban blood transfusion centre in Dar‐es‐Salaam, Tanzania. Between October 2016 and March 2017 anonymized records of all donors registered at the blood transfusion unit were accessed to retrospectively note demographic information, donor status, first‐time status, transfusion‐transmitted infection result and notification. 6402 consecutive donors were screened for transfusion‐transmitted infections; the majority were family/replacement blood donors (88.0%) and male (83.8%). Overall transfusion‐transmitted infections prevalence was 8.4% (95% CI 7.8‐9.1), with hepatitis B being the most prevalent infection (4.1% (95% CI 3.6‐4.6)). Transfusion‐transmitted infections were more common in family/replacement blood donors (9.0% (95% CI 8.3‐9.8)) as compared to voluntary nonremunerated blood donor (4.1% (95% CI 2.8‐5.7)). A minority of infected‐donors were notified of a positive result (8.5% (95% CI 6.3‐11.2)). Although transfusion‐transmitted infections are more prevalent among family/replacement blood donors, overall risk of transfusion‐transmitted infections across all groups is considerable. In addition, existing efforts to notify donors of a positive transfusion‐transmitted infection are poor. Future policies must focus on improving linkage to care for newly diagnosed patients with transfusion‐transmitted infections.

tional blood transfusion policy, 100% of donations being screened for TTIs and having at least 80% of donation from voluntary nonremunerated blood donors (VNRD). 6 Compliance with these directives has been variable among the African member states. For example, in Tanzania like in many sub-Saharan African countries, there remains a heavy reliance on family/replacement blood donors (FRD); however, Tanzania has implemented a national blood transfusion policy and systematic screening of TTIs. 7 Screening for TTIs also provides an important opportunity for notification and linkage to care of donors. As part of its HIV and viral hepatitis elimination strategies, the WHO has set out ambitious objectives to improve diagnosis and care for HIV and viral hepatitis. 8,9 Thus, TTI positive blood donors are an ideal population to transition to specialist care. To date, there has been minimal description of TTI linkage to care in blood transfusion settings in SSA, with existing reports limited to West African studies from Burkina Faso, Ghana and The Gambia. 4,10,11 This article aims to (a) describe the overall prevalence of TTIs among donors attending one of the largest blood transfusion centres in Dar-es-Salaam, Tanzania, (b) compare the TTI prevalence between FRD and VNRD and (c) describe existing linkage to care for TTIs as defined by donor notification of a positive result and referral to respective clinical services. In addition, candidates must be aged 18-69 years, weight >50 kg and must not be anaemic (defined as ≥12.5 g/d for females and ≥13.5 g/d for males).

| Serological methods used to detect HIV, HBV, HCV and syphilis
During the study period, all blood donors had samples tested locally for TTIs. The HIV antigen/antibody combination, HBV surface antigen (HBsAg) and anti-HCV assays were performed on the Abbott ARCHITECT platform (Abbott Laboratories, Chicago, IL) in accordance with the manufacturer's specifications. Syphilis serology was performed using the syphilis 3.0 SD Bioline rapid diagnostic test (SD Biostandard Diagnostics Private Limited, Gurgaon, Haryana, India).

| Data collection
For each donation entry, a range of data was recorded, including demographics (age and gender); donor status (first time or repeat); type of donation (voluntary or family/replacement); TTI status (HIV Ag/Ab, HBsAg, anti-HCV Ab, syphilis serology); and evidence of the donors returning to collect the screening data from the unit.
OR adjusted for age and sex for all variables.

| Statistical analysis
Characteristics of the study participants were presented by mean and standard deviation (SD) for the continuous variables and percentage for the categorical variables. Continuous variables were compared using the student's t test and categorical variables using the chi-squared test or Fisher's exact test where appropriate.
Prevalence and their 95% binomial confidence intervals (CI) were calculated. Factors associated with TTI were identified using a logistic regression. We predetermined the following variables as potential determinants for TTI: age, sex, donor status (first time or repeat) and type of donation (voluntary or family/replacement). For all the variables, we systematically adjusted for potential distal determinants (age and sex), irrespective of the results of the univariable analyses.
Factors with a P-value of less than 0.05 were considered statistically significant. R statistical computing freeware version 3.4.3 was used for all analyses.  Table 1. Donors were predominantly males (n = 5383 (84.1%)), and the mean age was 34.7 (SD 9.8) years. FRDs accounted for the vast majority of donations (n = 5634 (88%)) of whom more than half (n = 3154 (56%)) were first-time donors. Conversely, the VNRDs minority was overwhelmingly made up by repeat donors (n = 662 (86.7%)).

| D ISCUSS I ON
The increased requirements and shortage in supply of blood in Africa are well documented. The recent WHO global report highlights the disparity in availability of blood across the globe, with supplies of blood in Africa falling woefully shy of the recommended threshold of 10 units/1000 people. 3 In Tanzania, the existing supply stands at 3.6 units/1000, with the majority of blood obtained through FRD. 7 This is highlighted in our study, where close to 90% of all donations were from FRD. A recent review of blood donation practice in SSA reflected similar practice, with 24 out of 34 published articles reporting donor status either partially or completely relying on FRD or commercial donation. 12 In contrast, the WHO global report on blood transfusion safety reported that 67% of blood donations from the African region were from VNRD. 3 There has been a growing impetus to improve global blood transfusion safety, which includes improved screening for TTIs. As recently as 2004 a report commissioned on transfusion safety in Africa reported that 88.5% of blood donated across 40 different countries had not been reliably tested for HIV. 13 In 2006, it was reported that only 40, 34 and 23 out of 46 African countries surveyed systematically screened all blood products for HIV, HBV and HCV respectively. 13 Further improvement was seen by 2013 estimates, where less than 10% of blood was not screened for all TTIs. 3 One of the most cited issues with universal TTI screening is guaranteed supply There is a fine balance to be struck by restricting the supply of blood without compromising demand, particularly in SSA where in the majority settings the existing system is already stretched. 19 The repercussions of adopting this policy have been documented in Malawi, where it is reported that per capita blood donations dropped between 2011 and 2014, resulting in two-thirds of the national transfusion need being unmet. 20 In addition, the economic impact of a VNRD system is a 4-8-fold increase in cost per unit of blood, which is of particular relevance to resource-limited settings. 12,21 It has been previously argued that a direct comparison of TTI prevalence between FRD and VNRD without taking into account first-time/repeat donor status introduces a significant selection bias.
Allain and colleagues have previously described that TTI prevalence in first-time VNRD is equivalent to FRD and thus have proposed that a more sustainable model for blood transfusion in SSA is one based on repeat donors, irrespective of VNRD or FRD status. 12,22 However, the findings from our study indicate that this notion may not be completely reflective in this cohort. We found that TTI prevalence was highest among FRD, irrespective of first-time or repeat status (9.1% (95% CI 8.0-10.3) and 9.0% (95% CI 8.0-10.1) respectively). Although the proportion of first-time VNRD was comparably small, the prevalence was lower among first-time VNRD (6.9% (95% CI 2.8-13.8), while repeat VNRD represent the lowest risk (3.6% (95% CI 2.3-5.4) ( Table 4).
In particular, it is interesting to note that cases of HIV and HCV were more common in the FRD group compared with first-time VNRD. In the case of HIV, this may represent a proportion of undisclosed infections given the existing stigma associated with HIV.
While transmission of HCV through injecting drug use is an underappreciated problem, 23 and since it is considered a taboo practice, it is also likely to be undisclosed. Conversely, HBV and syphilis appear to be relatively similar in both donor groups, which may underline a general lack of awareness of TTI status across all donor groups.
Mode of transmission is also an important determinant. In Africa, HBV is transmitted early in life 24  and 2% for HBV. 11 Thus, further reports describing linkage pathways and treatment outcomes of patients successfully identified through this process are necessary. 10 However, we can assume that linkage to care of positive donors in our setting is very poor given the low rate of notification.
Despite much higher prevalence of TTIs in FRD as compared to VNRD, our study highlights that the main blood transfusion centre in Tanzania