Cost effectiveness of adding nucleic acid testing to hepatitis B, hepatitis C, and human immunodeficiency virus screening of blood donations in Zimbabwe

BACKGROUND

The aim of this study was to assess the cost effectiveness of introducing individual-donation nucleic acid testing (ID-NAT), in addition to serologic tests, compared with the exclusive use of serologic tests for the identification of hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) I and II among blood donors in Zimbabwe.

STUDY DESIGN AND METHODS

The costs, health consequences, and cost effectiveness of adding ID-NAT to serologic tests, compared with serologic testing alone, were estimated from a health care perspective using a decision-analytic model.

RESULTS

The introduction of ID-NAT in addition to serologic tests would lower the risk of HBV, HCV, and HIV transmission to 46.9, 0.3, and 2.7 per 100,000 donations, respectively. ID-NAT would prevent an estimated 25, 6, and 9 HBV, HCV, and HIV transfusion-transmitted infections per 100,000 donations, respectively. The introduction of this intervention would result in an estimated 212 quality-adjusted life-years (QALYs) gained. The incremental cost-effectiveness ratio is estimated at US$17,774/QALY, a value far more than three times the gross national income per capita for Zimbabwe.

CONCLUSION

Although the introduction of NAT could further improve the safety of the blood supply, current evidence suggests that it cannot be considered cost effective. Reducing the test costs for NAT through efficient donor recruitment, negotiating the price of reagents, and the efficient use of technology will improve cost effectiveness.

Incidence of haemolytic disease of the newborn in Harare, Zimbabwe

BACKGROUND

Haemolytic Disease of Newborn is responsible for a number of neonatal deaths and complications worldwide. Its incidence in Zimbabwe is not clearly understood.

OBJECTIVE

To find out incidence of Haemolytic Disease of Newborn in Harare and ability to identify antibodies associated with HDN.

METHODS

A retrospective cross sectional study at the Parirenyatwa Group of Hospitals and National Blood Service, Zimbabwe (NBSZ). We studied 22493 infants at Parirenyatwa Hospital during the 1995-1997 and 2002-2003 periods. The main outcome measures were ABO and Rh blood group results, Direct Antiglobulin Test and Maternal Antibody Screening and Identification Results were obtained from the NBSZ.

RESULTS

One hundred and ninety-one (0.85%) infants had Haemolytic Disease of Newborn. One hundred and sixty-three (85.34%) of these were due to anti-AB, twenty five (13.09%) were due to anti-D and three (1.57%) due to anti-Kell. Incidence of Haemolytic Disease of Newborn during 1995-1997 and 2002-2003, were 0.93% and 0.64%, respectively (p = 0.014). ABO Haemolytic Disease of Newborn showed a statistically significant difference during the two periods (p = 0.003). Rhesus Haemolytic Disease of Newborn showed no statistically significant difference during same periods (p = 0.317).

CONCLUSION

The incidence of Haemolytic Disease of Newborn at Parirenyatwa Hospital is comparable with that found in other countries. It is recommended that K antigen be included in the pretransfusion testing to avoid anti-K related Haemolytic Disease of Newborn.

Demographic and social characteristics of regular donors who sero-converted in Harare

Zimbabwe, like any other country, is currently experiencing a fast growing HIV/AIDS pandemic. A considerable number of infections are caused by blood transfusion. The aim of this study is to determine risk factors, events and socio-demographic characteristics associated with incidence of HIV infections and to prevent sero-conversion of regular blood donor. A retrospective cross sectional study was done. 22,922 regular donors at National Blood Transfusion Services in Harare were used. The number of all regular donors who sero-converted and their status during the 1999 to 2001 period were determined. About 327 (1.4%) of the regular donors sero-converted. Two hundred and seventy-four (84%) were males and 53(16%) were females. 52.6% of the males were married, 46.7% were single and .7% separated. 30.2% of the females were married, single women 67.9% and separated women 1.9%. Increased sero-conversion was associated with unemployment, high-density area residence and the sexually active age group (21 to 45 year olds). There was an association between gender and marital status among sero-converters (c2 = 8.48; P-value = 0.014) and males were likely to be older than females (t = 2.9; P-value = 0.0019). It can be concluded that unemployment and living in high-density residential areas are highly associated with HIV sero-conversion among regular donors. Single females, working class males and the sexually active age group are highly exposed to risk factors. It is recommended that donor education schemes and knowledge of these factors should be considered during donor recruitment.

Prevalence of HIV infection in school based and other young donors during the 2002 and 2003 period

The majority of donor blood in Zimbabwe comes from school-based donors. Zimbabwe has one of the highest HIV prevalences in the world and the age at which the infection is acquired is decreasing. This is a serious threat to the safety of blood supply. The prevalence of HIV has been low among the youth the majority of whom are still going to school and between the ages of sixteen and nineteen years. However, due to the changing socio-economic environment, sexual behavioural patterns have also changed. It is now necessary to evaluate these changes in order to guarantee safe blood transfusion. To determine the prevalence of HIV among adolescent donors during the period between 2002 and 2003. Cross-sectional retrospective study, National Blood Transfusion Service (NBTS). All school based donors and others between 16 and 19 years of age. The number of donors who were HIV positive in this age group. Data on donors was collected from computer files at the National Blood Transfusion Service (NBTS) Information Technology (IT) department. Prevalence of HIV was determined and categorised according to gender, age and the type of school the donor attended. The prevalence of HIV in 2002 and 2003 were 0.48% and 0.38%, respectively. Sixty-six per cent (66%) of HIV positive donors had donated for the first time. The prevalence in both periods was much higher in female donors than male donors. In 2002 males and females had prevalence of 0.28% and 0.66%, respectively. In 2003 males and females had prevalence of 0.18% and 0.55%, respectively. The overall highest prevalence (0.90%) was found between the 16-19 year age group who were not going to school (others). In 2002 female day schools had the highest (0.87%). The lowest prevalence (0%) was found in male boarding schools. In 2003 the highest prevalence (1.61%) was found in the 16-19 year age group who were not going to school (others). The lowest prevalence (0) in the same year was found in male boarding scholars. It can be concluded that the majority of HIV positive school based donors are first time donors. Female scholars and those of the same age group who are not going to school have the highest risk of donating HIV positive blood than male donors. The prevalence of HIV in adolescent blood donors decreased with age. It is recommended that active donor recruitment should be in favour of the low prevalence groups.

The prevalence of Herpes simplex virus type-2 infection in blood donors in Harare, Zimbabwe

OBJECTIVE

To determine the prevalence of HSV-2 infections in a population of blood donors.

DESIGN

Cross sectional study.

SETTING

Harare Blood Transfusion Service (BTS) Centre.

SUBJECTS

314 serum specimens of voluntary blood donors.

MAIN OUTCOME MEASURES

HSV-2 sero-prevalence.

RESULTS

The median age (Q1, Q3) of the blood donors was 18 (17,27) years and 65% of them were males. HSV-2 infection was detected in 29 (9.7%) of the 299 specimens that were analyzed. There was a strong association between age of blood donors and HSV-2 seropositivity (p < 0.001). Older blood donors tended to be positive while younger donors tended to be negative for HSV-2 antibodies. Though not as strong, there was also an association between HSV-2 and HIV seropositivity (p = 0.048).

CONCLUSION

The prevalence of HSV-2 infections in blood donors in Harare is high, considering the nature of the population studied. Therefore, the testing for HSV-2 in the serum of prospective blood donors should be included in the screening profiles used at the BTS centre in Harare, Zimbabwe to improve blood and blood products.

Risk factors for HIV seropositivity among first-time blood donors in Zimbabwe

BACKGROUND

Factors associated with an increased likelihood of HIV infection among newly recruited blood donors in Zimbabwe are identified. Their feasibility as criteria for exclusion from donation is assessed.

STUDY DESIGN AND METHODS

A self-administered survey including demographic and behavioral questions was completed by 1199 first-time, volunteer blood donors in Harare, Zimbabwe. Methods for subject recruitment and laboratory screening followed usual blood bank protocols.

RESULTS

Fifteen percent of subjects were HIV positive. Factors significantly associated with HIV seropositivity at the p<0.05 level included recruitment venue, age, marital status, donor residence, residence of primary partner, occupation, history of sexually transmitted disease, and condom use. An exclusion strategy based on donor age, condom use, recruitment venue, sexually transmitted disease history, and residence of primary partner would exclude a large proportion of HIV-infected donors without substantial loss of uninfected donors.

CONCLUSIONS

Exclusion of donors who are likely to be infected with HIV is a sound policy for improving blood safety and reducing operating costs worldwide. Identification of efficient donor selection criteria requires knowledge of the local epidemiology of HIV infection and the asking of questions that are likely to be answered accurately.

Risk factors for prevalent and incident HIV infection in a cohort of volunteer blood donors in Harare, Zimbabwe: implications for blood safety

OBJECTIVES

To compare risk factors for HIV seropositivity with risk factors for HIV seroconversion in a population of volunteer blood donors in Harare, Zimbabwe, and to assess the impact of risk factor exclusion strategies on the safety of the blood supply.

DESIGN

A secondary analysis of a longitudinal cohort study was performed.

SUBJECTS AND METHODS

The subjects were volunteer blood donors who were also taking part in a prospective cohort study in Harare, Zimbabwe. They were tested for HIV antibodies upon enrollment and at 6-month intervals. Their donation history, age, marital status and the presence or absence of multiple sex partners and paying for sex were assessed as predictors of HIV seropositivity and HIV seroconversion. The impact of exclusion strategies on blood safety was modeled by estimating the number of HIV-infected units that would escape detection by antibody screening if blood donors with these risk factors were excluded.

RESULTS

The HIV seroprevalence among persons accepted for blood donation was 8.8%; the HIV seroincidence was 2.1 per 100 person-years. Significant risk factors for HIV seropositivity were being a new donor (odds ratio 7.3, 95% confidence interval 4.4-1 2.1), age over 25 years (odds ratio 1.6, confidence interval 1.1-2.4), being married (odds ratio 1.7, confidence interval 1.2-2.6), paying for sex (odds ratio 2.6, confidence interval 1.7-3.9) and multiple sex partners (odds ratio 2.1, confidence interval 1.4-2.9). Significant risk factors for HIV seroconversion were age under 25 years (hazard ratio 2.5, confidence interval 1.4-5.0) and being unmarried (hazard ratio 2.5, confidence interval 1.4-5.0). Of note, age and marital status reversed their direction of association with respect to HIV seropositivity and HIV seroconversion. Exclusion strategies based on strong predictors of HIV seroconversion were the most effective in improving the safety of the blood supply.

CONCLUSIONS

A distinction between risk factors for HIV seropositivity and HIV seroconversion is necessary in order to develop strategies to reduce the residual risk of transfusion-associated HIV transmission. Because window-period donations are the most important source of residual HIV contamination and arise from incident infections, research to develop risk factor exclusion strategies must focus on predictors of HIV seroconversion.

Epidemiology and prevention of transfusion-associated human immunodeficiency virus transmission in sub-Saharan Africa

BACKGROUND AND OBJECTIVES

Compared to industrialised nations, countries in sub-Saharan Africa experience a greater amount of transfusion-associated HIV transmission due to high rates of transfusion in some groups of patients, a higher incidence and prevalence of HIV infection in donor populations, a lack of HIV antibody screening in some areas, and a higher residual risk of contamination in blood supplies despite antibody screening.

MATERIALS AND METHODS

Epidemiologic review.

RESULTS

Epidemiologic evidence supports the effectiveness of three relatively inexpensive strategies to prevent transfusion-associated HIV transmission in sub-Saharan Africa: HIV antibody screening, avoidance of unnecessary use of blood products, and exclusion of donors at high risk of infection. Such prevention strategies have not been universally implemented.

CONCLUSIONS

International aid to establish and maintain HIV antibody screening programmes, implementation of sound criteria for transfusion, and the search for HIV risk factors to use as donor exclusion criteria must be expanded in the region.

Rapid and simple hepatitis assays: encouraging results from a blood donor population in Zimbabwe

A rapid assay to detect antibodies to hepatitis C virus (HCV) in serum and two rapid/simple assays to detect hepatitis B surface antigen (HBsAg) in whole blood/serum were evaluated for their accuracy and suitability at the National Blood Transfusion Service, Harare, Zimbabwe. For this purpose, a total of 206 sera (196 routinely collected and 10 frozen) were tested using the HCV-SPOT (Genelabs Diagnostics), the SimpliRED HBsAg test (AGEN), and the Dipstick-HBsAg (PATH/Immuno-Chemical Laboratories). The results were compared with those obtained using a routine HBsAg enzyme immunoassay (EIA) (Auszyme, Abbott) and an HCV IgG second-generation EIA (Abbott). An HCV IgM test (Abbott) was used for samples that produced discordant results, and all HCV-reactive samples were confirmed using the INNO-LIA HCV Ab III synthetic peptide assay (Innogenetics). Overall, the concordance between the HCV-SPOT and the HCV EIA was 97.6% (201/206). For the 193 sera that were true HCV negatives, the number of false positives was six with the HCV-SPOT test, while the HCV EIA produced three (specificity = 97.0% and 98.5%, resp.). Of these false positives, two were so in both tests. None of the false positives contained IgM antibodies to HCV, and there were no false negatives in the two HCV tests. The concordance between the two rapid HBsAg tests and the HBsAg EIA was 99.5% (205/206). All the rapid/simple tests were easy to perform and interpret, required no (or minimal) laboratory equipment, and could be taught easily to local laboratory personnel. The cost of these tests is equivalent to or less than that of routine EIA methods.

Deferral of blood donors with risk factors for HIV infection saves lives and money in Zimbabwe

We compared the cost-effectiveness of three strategies to avert transfusion-associated HIV infection in Zimbabwe: HIV antibody testing, deferral of donors with HIV risk factors, and deferral of donors with risk factors followed by antibody testing ("Defer/Test"). The Defer/Test strategy averted the most HIV infections. Compared with antibody testing alone, the Defer/Test strategy, using history of genital ulcer or any sexually transmitted disease as a criterion for deferral, resulted in net savings. The cost per HIV-infected unit averted using history of paying for sex or having had multiple sex partners was $ 127 and $ 773, respectively. We discern four benefits of risk factor-based deferral before antibody testing. First, deferring donors at risk lessens collection of blood in the window period. Second, deferring donors likely to be HIV positive minimizes the number of units discarded. Third, ascertainment of donor risk provides an opportunity for AIDS education and prevention. Fourth, the number of false negatives is lower with a lower HIV prevalence among accepted donors. The Defer/Test strategy is cost-effective in Zimbabwe because additional recruitment costs are offset by discarding fewer HIV-positive units. We predict the Defer/Test strategy will be cost-effective in other sub-Saharan African donor populations.

Characteristics of anti-A and anti-B in black Zimbabweans

Sera from young, black, group 0 Zimbabwean blood donors were screened for anti-A and anti-B haemolysins. Nearly one fifth of the sera were found to be strongly haemolytic for either A or B cells or both. Some of the sera were titrated for agglutination in saline before and after treatment with dithiothreitol. Serum dilutions beyond the endpoint of agglutination were further tested by the indirect antiglobulin technique using specific anti-IgM and anti-IgG sera. More than 60% of the strongly lytic sera had high titres of IgG (> or = 64). The IgM and IgG concentrations both of anti-A and anti-B were correlated and these levels were in turn correlated with haemolytic activity.

Distribution of HLA-DQA1, -DQB1 and DRB1 alleles in black IDDM patients and controls from Zimbabwe

We have used the XI Histocompatibility Workshop sequence-specific oligonucleotide probes to determine the DRB1, DQA1 and DQB1 genotypes by dot-blot hybridization of polymerase chain reaction (pcr)-amplified material from a homogenous black population in Zimbabwe. The DR4 subtype DRB1*0405, the DR3 subtype DRB1*0301, DQB1*0201 and DQB1*0302 and DQA1*0301 and DQA1*0501 were significantly increased in the IDDM group compared to the controls, whereas DRB1*11, DQB1*0602 and DQA1*0102 were significantly decreased. Taken together, the data show that susceptibility and resistance to IDDM are associated both with particular haplotypes and DQA1-DQB1 heterodimers without one or other being overriding.