Background

Improving blood safety without introducing nucleic acid testing in blood screening may be possible using antigen/antibody (Ag/Ab) combination assays, especially in resource-poor countries.

Study design and methods

To evaluate the potential reduction of human immunodeficiency virus (HIV)-transmitted infection using such an assay, a study was carried out aimed to compare the routine strategy for blood screening (S1), combining a rapid test (Determine HIV-1/-2, Inverness) and an enzyme immunoassay (human HIV-1/-2, Human Diagnostic) with an HIV Ag/Ab assay (S2, Genscreen ULTRA HIV Ag-Ab, Bio-Rad) in 2000 blood donations tested in Cameroon. Western blot and HIV RNA polymerase chain reaction were used to confirm the infection in reactive donors, and genotype was determined in HIV RNA-positive samples.

Results

Of the 2000 donors, 3.1% were positive with S1 and 4.3% with S2. Of the 97 samples positive with S1 and/or S2 tested for confirmation, 54.7% were positive, 38.1% indeterminate, and 7.2% negative. There were significant differences between S1 and S2 in terms of sensitivity (S1, 79.2%; S2, 100%), irrespective of the genotype, and in specificity (S1, 99.0; S2, 98.3%). The most frequent genotype (49%) was CRF02_AG.

Conclusions

A testing strategy using Genscreen ULTRA HIV Ag/Ab could prevent 55 HIV transmissions per 10,000 donations. However, this would be at a cost of discarding 170 per 10,000 negative donations that would test false positive, showing that the implementation of new techniques in blood screening need an optimization before routine use. Using confirmatory assays, HIV Ab prevalence in blood donors in Cameroon was estimated at 2.65%.

In low-income-countries, screening for hepatitis C virus (HCV) infection is often based on rapid tests (RT). Their lower sensitivity compared to enzyme immunoassay (EIA) suggests that newer HCV Antigen/Antibody (Ag/Ab) combination assays might have a role in such countries. To test this idea, 1998 blood donors were tested at the University Teaching Hospital blood bank in Yaoundé, Cameroon simultaneously with a RT (HCV rapid test, Human Diagnostics, Berlin, Germany) according to standard practice (S1) and with an Ag/Ab assay (Monolisa HCV Ag/Ab Ultra, Biorad, France) (S2). All discordant, borderline and reactive samples were submitted to confirmatory testing by immunoblot and/or HCV-RNA. Of the 86 (4.3%) samples positive with one or both strategies, 29 were confirmed negative, 37 positive and 20 were false positive or resolved infection. There was a significant difference in test sensitivity (p=0.01) between S1 (70.3%) and S2 (91.9%) but not in test specificity (99.4% and 98.6%, respectively). The benefit of the Ag/Ab assay in the detection of recent HCV seronegative infections could not be evaluated since no Antigen-only donations were identified. However, better Ag/Ab test sensitivity compared to RT supports the implementation of these newer immunoassays for HCV screening in the African blood bank setting.

Objectives

As sex between men is a major route of human immunodeficiency virus (HIV) infection in most western countries, restrictive deferral rules for blood donation have largely been implemented regarding men having sex with men (MSM). Here, we sought here to assign unreported HIV risk factors in blood donors (BDs) and reevaluated the MSM-associated fraction of HIV transfusion residual risk (%RR_MSM ).

Methods

We applied a genetic distance-based approach to infer an HIV transmission network for 384 HIV sequences from French BDs and 1337 HIV sequences from individuals with known risk factors (ANRS PRIMO primary HIV infection cohort). We validated the possibility of assigning a risk factor according to clustering using assortative mixing. Finally, we recalculated the %RR_MSM .

Results

A total of 81 of 284 (28.5%) male and 5 of 100 (5%) female BDs belonged to a cluster; 72 (88.9%) of the 81 male BDs belonged to MSM clusters. After cluster correction, 8 of 67 (11.9%), 4 of 21 (19.0%), and 19 of 88 (21.6%) HIV-positive (HIV+) male BDs with heterosexual, other, or unknown risk factors could be reclassified as MSM, accounting for 10.9% of the total HIV+ male BDs. Overall, 139 of 284 HIV+ male donors (48.9%) could be considered MSM between 2000 and 2016 in France. Between 2005 and 2016, the %RR_MSM increase varied from 0 to 19%, without differing significantly from the %RR_MSM before reclassification.

Conclusion

Network inference can be used to complement declaration data on risk factors for HIV infection in BDs. This approach, complementary to behavioral studies, is a valuable tool to evaluate the effect of changes in deferral criteria on BD compliance.

Background

Sub-Saharan Africa remains the epicenter of the human immunodeficiency virus (HIV) pandemic. However, there is a lack of multicenter data on the risk of transfusion-transmitted HIV from blood centers in sub-Saharan Africa.

Study design and methods

The incidence of HIV infections in the blood donations collected in the main blood banks of five countries (Burkina Faso, Congo, Ivory Coast, Mali, and Senegal) was determined to estimate the current transfusion risk of HIV infection using the incidence rate/window period model.

Results

The risk of transfusion-transmitted HIV infections associated with the window period varied from 1 in 90,200 donations (Senegal) to 1 in 25,600 (Congo). Considering the five participating blood centers as a whole, the incidence rate of HIV-positive donors per 100,000 person-years was 56.6 (95% confidence interval [CI], 47.1-67.9); the residual risk (RR) was 34.1 (95% CI, 7.8-70.7) per 1 million donations, which represents 1 in 29,000 donations (95% CI, 1/128,000-1/14,000).

Conclusion

RR estimates varied according to the country. This is potentially due to a lower incidence of HIV infection in the general population or to a more efficient selection of blood donors in the countries with the lowest risk. The estimates of the transfusion risk of HIV infection in each country are important, both to assess the impact of current preventative strategies and to contribute data to policy decisions to reinforce transfusion safety.

Background

Following World Health Organization recommendations that a quality control (QC) system be implemented in African blood centers, a pilot study of the performance of human immunodeficiency virus antibody (anti-HIV), hepatitis B surface antigen (HBsAg), and hepatitis C virus antibody (anti-HCV) testing by several Sub-Saharan African blood centers was initiated.

Study design and methods

A reference laboratory sent a panel of 25 samples to six African blood center laboratories. The panel included eight negative samples; four anti-HIV-1–, one anti-HIV-2–, four anti-HCV–, and five HBsAg-positive samples; and three samples consisting of mixtures of two sera to mimic coinfections. Sensitivity, specificity, and overall quality (correct positive or negative status) scores were calculated.

Results

From the 21 sets of results obtained (seven for each virus), eight were from rapid tests (two for HIV, three for HBV, and three for HCV) and 13 were from enzyme immunoassays (EIAs; all HIV EIAs were antigen/antibody combination assays). Overall assay sensitivity was 98% for HIV, 75% for HBV, and 88% for HCV; agreement between blood centers using the same assay was good. Sensitivity of rapid tests was notably poorer than EIAs, with overall sensitivity quality scores of 64.5% for rapid tests (20% for HBsAg rapid tests) compared to 100% for EIAs. The overall specificity quality scores were 98.3 and 94.5% for EIAs and rapid tests, respectively.

Conclusions

This pilot QC study organized for blood centers of Sub-Saharan Africa showed the feasibility of the approach despite some logistic constraints. Although interlaboratory variability was small, the poor performance of rapid tests, especially for HBsAg, raises policy questions about their use as the only screening assay.

A 2014 report evaluating accuracy of serologic testing for transfusion-transmissible viruses at African blood center laboratories found sensitivities of 92%, 87%, and 90% for detecting infections with human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV), respectively (1). Following substantial investments in national blood transfusion service (NBTS) laboratories, in 2017 investigators tested proficiency at 84 blood center laboratories (29 NBTS and 55 non-NBTS) in seven African countries. A blinded panel of 25 plasma samples was shipped to each participating laboratory for testing with their usual protocols based on rapid diagnostic tests (RDTs) (2) and third and fourth generation enzyme immunoassays (EIA-3 and EIA-4). Sensitivity and specificity were estimated using separate regression models that clustered assays by laboratory and adjusted for assay type and NBTS laboratory status. Mean specificities were ≥95% for all three viruses; however, mean sensitivities were 97% for HIV-positive, 76% for HBV-positive, and 80% for HCV-positive samples. Testing sensitivities for all viruses were high when EIA-3 assays were used (≥97%). Lower sensitivities for HBV-positive samples and HCV-positive samples were associated with assay types other than EIA-3, used primarily by non-NBTS laboratories. Proficiency for HIV testing has improved following international investments, but proficiency remains suboptimal for HBV and HCV testing. In sub-Saharan African blood centers, the quality of rapid tests used for HBV and HCV screening needs to be improved or their use discouraged in favor of EIA-3 tests.

A serological survey of 2,430 archived serum samples collected between 1997 and 2012 was conducted to retrospectively determine the prevalence of Marburg virus in five African countries. Serum samples were screened for neutralizing antibodies in a pseudotype micro-neutralization assay and confirmed by enzyme-linked immunosorbent assay (ELISA). Surprisingly, a seroprevalence for Marburg virus of 7.5 and 6.3% was found in Cameroon and Ghana, respectively, suggesting the circulation of filoviruses or related viruses outside of known endemic areas that remain undetected by current surveillance efforts. However, due to the lack of validated assays and appropriate positive controls, these results must be considered preliminary.

We conducted a serologic survey of 2,430 serum samples collected during 1997-2012 for various studies to determine the prevalence of the hemorrhagic fever virus Ebola virus (EBOV) in equatorial Africa. We screened serum samples for neutralizing antibodies by using a pseudotype microneutralization assay and a newly developed luciferase immunoprecipitation system assay. Specimens seroreactive for EBOV were confirmed by using an ELISA. Our results suggest a serologic prevalence of 2%-3.5% in the Republic of the Congo and the Democratic Republic of the Congo, which have reported outbreaks of infection with EBOV. In addition we detected a seroprevalence of 1.3% in southern Cameroon, which indicated a low risk for exposure in this region.

Human parvovirus 4 infections are primarily associated with parenteral exposure in western countries. By ELISA, we demonstrate frequent seropositivity for antibody to parvovirus 4 viral protein 2 among adult populations throughout sub-Saharan Africa (Burkina Faso, 37%; Cameroon, 25%; Democratic Republic of the Congo, 35%; South Africa, 20%), which implies existence of alternative transmission routes.