Pitfalls with rapid HIV antibody testing in HIV-infected children in the Western Cape, South Africa

Understanding low sensitivity of community-based HIV rapid testing: experiences from the HPTN 071 (PopART) trial in Zambia and South Africa

Introduction: Population-wide HIV testing services (HTS) must be delivered in order to achieve universal antiretroviral treatment (ART) coverage. To accurately deliver HTS at such scale, non-facility-based HIV point-of-care testing (HIV-POCT) is necessary but requires rigorous quality assurance (QA). This study assessed the performance of community-wide HTS in Zambia and South Africa (SA) as part of the HPTN 071 (PopART) study and explores the impact of quality improvement interventions on HTS performance.

Methods: Between 2014 and 2016, HIV-POCT was undertaken within households both as part of the randomly selected HPTN 071 research cohort (Population Cohort [PC]) and as part of the intervention provided by community HIV-care providers. HIV-POCT followed national algorithms in both countries. Consenting PC participants provided a venous blood sample in addition to being offered HIV-POCT. We compared results obtained in the PC using a laboratory-based gold standard (GS) testing algorithm and HIV-POCT. Comprehensive QA mechanisms were put in place to support the community-wide testing. Participants who were identified as having a false negative or false positive HIV rapid test were revisited and offered retesting.

Results: We initially observed poor sensitivity (45–54%, 95% confidence interval [CI] 31–69) of HIV-POCT in the PC in SA compared to sensitivity in Zambia for the same time period of 95.8% (95% CI 93–98). In both countries, specificity of HIV-POCT was >98%. With enhanced QA interventions and adoption of the same HIV-POCT algorithm, sensitivity in SA improved to a similar level as in Zambia.

Conclusions: This is one of the first reports of HIV-POCT performance during wide-scale delivery of HTS compared to a GS laboratory algorithm. HIV-POCT in a real-world setting had a lower sensitivity than anticipated. Appropriate choice of HIV-POCT algorithms, intensive training and supervision, and robust QA mechanisms are necessary to optimize HIV-POCT test performance when testing is delivered at a community level. HIV-POCT in clients who did not disclose that they were on ART may have contributed to false negative HIV-POCT results and should be the topic of future research.

HIV point of care diagnosis: preventing misdiagnosis experience from a pilot of rapid test algorithm implementation in selected communes in Vietnam

INTRODUCTION

In Vietnam, HIV testing services had been available only at provincial and district health facilities, but not at the primary health facilities. Consequently, access to HIV testing services had been limited especially in rural areas. In 2012, Vietnam piloted decentralization and integration of HIV services at commune health stations (CHSs). As a part of this pilot, a three-rapid test algorithm was introduced at CHSs. The objective of this study was to assess the performance of a three-rapid test algorithm and the implementation of quality assurance measures to prevent misdiagnosis, at primary health facilities.

METHODS

The three-rapid test algorithm (Determine HIV-1/2, followed by ACON HIV 1/2 and DoubleCheckGold HIV 1&2 in parallel) was piloted at CHSs from August 2012 to December 2013. Commune health staff were trained to perform HIV testing. Specimens from CHSs were sent to the provincial confirmatory laboratory (PCL) for confirmatory and validation testing. Quality assurance measures were undertaken including training, competency assessment, field technical assistance, supervision and monitoring and external quality assessment (EQA). Data on HIV testing were collected from the testing logbooks at commune and provincial facilities. Descriptive analysis was conducted. Sensitivity and specificity of the rapid testing algorithm were calculated.

RESULTS

A total of 1,373 people received HIV testing and counselling (HTC) at CHSs. Eighty people were diagnosed with HIV infection (5.8%). The 755/1244 specimens reported as HIV negative at the CHS were sent to PCL and confirmed as negative, and all 80 specimens reported as HIV positive at CHS were confirmed as positive at the PCL. Forty-nine specimens that were reactive with Determine but negative with ACON and DoubleCheckGold at the CHSs were confirmed negative at the PCL. The results show this rapid test algorithm to be 100% sensitive and 100% specific. Of 21 CHSs that received two rounds of EQA panels, 20 CHSs submitted accurate results.

CONCLUSIONS

Decentralization of HIV confirmatory testing to CHS is feasible in Vietnam. The results obtained from this pilot provided strong evidence of the feasibility of HIV testing at primary health facilities. Quality assurance measures including training, competency assessment, regular monitoring and supervision and an EQA scheme are essential for prevention of misdiagnosis.

Laboratory Innovation Towards Quality Program Sustainability

Laboratory innovation significantly affects program sustainability of HIV programs in low and middle income countries (LMICs) far beyond its immediate sphere of impact. Innovation in rapid development of diagnostic technologies, improved quality management systems, strengthened laboratory management, affordable external quality assurance and accreditation schemes, and building local capacity have reduced costs, brought quality improvement to point-of-care testing, increased access to testing services, reduced treatment and prevention costs and opened the door to the real possibility of ending the AIDS epidemic. However, for effectively implemented laboratory innovation to contribute to HIV quality program sustainability, it must be implemented within the overall context of the national strategic plan and HIV treatment programs. The high quality of HIV rapid diagnostic test was a breakthrough that made it possible for more persons to learn their HIV status, receive counseling, and if infected to receive treatment. Likewise, the use of dried blood spots made the shipment of samples easier for the assessment of different variables of HIV infection-molecular diagnosis, CD4+ cell counts, HIV antibodies, drug resistance surveillance, and even antiretroviral drug level measurements. Such advancement is critical for to reaching the UNAIDS target of 90-90-90 and for bringing the AIDS epidemic to an end, especially in LMICs.

Assessing the sensitivity and specificity of First Response HIV-1-2 test kit with whole blood and serum samples: a cross-sectional study

Background

Human immunodeficiency virus (HIV) Rapid diagnostic Test (RDT) kits are the preferred assays for HIV testing in many countries. Prevention of Mother-to-Child Transmission, Know Your Status Campaigns, Blood-Safety, Voluntary Counseling and Testing are major strategies adapted to control transmission of the virus and the pivot of these interventions is either screening or diagnosing individuals through testing. There are reports of inconsistent sensitivity and specificity with whole blood and serum samples collected from the same individual. Little is known about the diagnostic characteristics of First Response HIV-1-2 RDT kit, used as a single test kit in national HIV prevention and control programmes. The debate has always centered on choosing between whole blood and serum in a case where a single test kit that runs on only blood specimen will be used for testing. The variations in specificities and sensitivities with whole blood and serum samples imply that some individuals who might be true positives will be missed and elude care. This study determined the best blood-based specimen type (whole blood or serum) that improves performance of First Response HIV RDT kit in detecting HIV-specific antibodies.

Methods

A hospital-based cross-sectional study was conducted on 280 HIV infected and non-infected patients from May 2015 to June 2015. Blood samples from each participant were separated into whole blood and serum, and tested on First Response HIV-1-2 kits (Premier Medical Corporation Ltd., Kachigam, India) using Electro-chemi-luminescence assay (ECLIA) as reference assay.

Results

First Response HIV-1-2 RDT kit showed 100 % sensitivity and 100 % specificity with whole blood specimen and 100 % sensitivity and 82.86 % specificity with serum specimen for the detection of HIV-1. The positive and negative predictive values were 100, 100 and 85.35, 82.86 % for whole blood and serum respectively.

Conclusion

Whole blood specimen(s) from an individual have higher specificity, positive and negative predictive values than serum. Whole blood is the primary specimen to use on First Response HIV-1-2 RDT kit when screening peripheral blood for HIV-1-specific antibodies.

Determination of HIV Status in African Adults With Discordant HIV Rapid Tests

BACKGROUND

In resource-limited settings, HIV infection is often diagnosed using 2 rapid tests. If the results are discordant, a third tie-breaker test is often used to determine HIV status. This study characterized samples with discordant rapid tests and compared different testing strategies for determining HIV status in these cases.

METHODS

Samples were previously collected from 173 African adults in a population-based survey who had discordant rapid test results. Samples were classified as HIV positive or HIV negative using a rigorous testing algorithm that included two fourth-generation tests, a discriminatory test, and 2 HIV RNA tests. Tie-breaker tests were evaluated, including rapid tests (1 performed in-country), a third-generation enzyme immunoassay, and two fourth-generation tests. Selected samples were further characterized using additional assays.

RESULTS

Twenty-nine samples (16.8%) were classified as HIV positive and 24 of those samples (82.8%) had undetectable HIV RNA. Antiretroviral drugs were detected in 1 sample. Sensitivity was 8.3%-43% for the rapid tests; 24.1% for the third-generation enzyme immunoassay; 95.8% and 96.6% for the fourth-generation tests. Specificity was lower for the fourth-generation tests than the other tests. Accuracy ranged from 79.5% to 91.3%.

CONCLUSIONS

In this population-based survey, most HIV-infected adults with discordant rapid tests were virally suppressed without antiretroviral drugs. Use of individual assays as tie-breaker tests was not a reliable method for determining HIV status in these individuals. More extensive testing algorithms that use a fourth-generation screening test with a discriminatory test and HIV RNA test are preferable for determining HIV status in these cases.

Reactivity of routine HIV antibody tests in children who initiated antiretroviral therapy in early infancy as part of the Children with HIV Early Antiretroviral Therapy (CHER) trial: a retrospective analysis

BACKGROUND

Early antiretroviral therapy (ART) and virological suppression can affect evolving antibody responses to HIV infection. We aimed to assess frequency and predictors of seronegativity in infants starting early ART.

METHODS

We compared HIV antibody results between two of three treatment groups of the Children with HIV Early Antiretroviral Therapy (CHER) trial, done from July, 2005, until July, 2011, in which infants with HIV infection aged 5·7-12·0 weeks with a percentage of CD4-positive T lymphocytes of at least 25% were randomly assigned to immediate ART for 96 weeks (ART-96W) or deferred ART until clinical or immunological progression (ART-Def). We measured antibody from all available stored samples for ART-96W and ART-Def at trial week 84 using three assays: fourth-generation enzyme immunoassay HIV antigen-antibody combination, HIV-1 and HIV-2 rapid antibody test, and quantitative anti-gp120 IgG ELISA. We also assessed odds of seropositivity with respect to age of ART initiation and cumulative viral load. The CHER trial was registered with ClinicalTrials.gov, number NCT00102960.

FINDINGS

The median age of the infants from when samples were taken (184 samples from 268 infants) was 92 weeks (IQR 90·6-93·4). More specimens from the ART-96W group were seronegative than from the ART-Def group by enzyme immunoassay (ART-96W 49 [46%] of 107 vs ART-Def eight [11%] of 75; p<0·0001) and rapid antibody test (54 [53%] of 101 vs eight [11%] of 74; p<0·0001). Median anti-gp120 IgG concentration was lower in the ART-96W group (230 μg/μL [IQR 133-13 129]) than in the ART-Def group (6870 μg/μL [1706-53 645]; p<0·0001). If ART was started between 12 and 24 weeks of age, odds of seropositivity were increased 13·7 times (95% CI 3·1-60·2; p=0·001) compared with starting it between 0 and 12 weeks. All children starting ART aged older than 24 weeks were seropositive. Cumulative viral load to week 84 correlated with anti-gp120 IgG concentrations (coefficient 0·54; p<0·0001) and increased odds of seropositivity (odds ratio 1·59 [95% CI 1·1-2·3]) adjusted for ART initiation age.

INTERPRETATION

About half of children starting ART before 12 weeks of age were HIV seronegative by almost 2 years of age. HIV antibody tests cannot be used to reconfirm HIV diagnosis in children starting early ART. Long-term effects of seronegativity need further study. Clear guidelines are needed for retesting alongside improved diagnostic tests.

FUNDING

Wellcome Trust, Medical Research Council, and National Institutes of Health.

Young age at start of antiretroviral therapy and negative HIV antibody results in HIV-infected children when suppressed

BACKGROUND

Negative results on standard HIV antibody tests have been described among HIV-infected children suppressed on antiretroviral therapy (ART) started early in life. Here, we describe the frequency and predictors of this phenomenon in a well characterized cohort of treated children.

METHODS

We selected samples from 103 HIV-infected children who started ART 14 months of age or less and from 122 children who started 6 months of age or less followed as part of two sequential clinical trials in Johannesburg, South Africa. Children had attained viral suppression on ART and had received ART for between 3 and 6.4 years (mean 4.3 years) when tested for HIV antibody using a standard ELISA (Genescreen HIV1/2 version 2; Bio-rad).

RESULTS

Only children 6 months of age or less when ART was started had negative antibody results when tested after suppression on ART several years later. Negative or low-positive antibody results were observed in 40.0, 37.0 and 27.8% of children starting ART less than 2 months of age, or starting during month 2 or 3, respectively. This dropped to 5.9, 3.5 and 5.3% if ART was started during month 4, 5 and 6, respectively. Higher CD4 percentage prior to ART initiation and no recorded intermittent viremia also predicted negative antibody results.

CONCLUSION

Testing negative on standard HIV antibody tests occurs fairly commonly among HIV-infected children who started ART 3 months of age or less and are virally suppressed. It would be prudent in clinical practice to avoid HIV antibody tests among virally suppressed, early-treated children to prevent unnecessary confusion.

Rapid Tests versus ELISA for Screening of HIV Infection: Our Experience from a Voluntary Counselling and Testing Facility of a Tertiary Care Centre in North India

Early and accurate diagnosis of human immunodeficiency virus (HIV) infection is essential for timely identification of patients needing antiretroviral therapy and for instituting HIV prevention strategies. The primary methodology for HIV testing has shifted from enzyme linked immunosorbent assay (ELISA) to rapid diagnostic tests (RDTs) in recent years, especially in resource limited settings. However, the diagnostic performance of RDTs is a matter of concern. In the present study the performance of an RDT being used as the initial test in serial testing based algorithm for HIV diagnosis was compared with ELISA. Seven hundred and eighty-seven sera, tested at the voluntary counselling and testing facility employing a serial testing algorithm (based on SD Bioline HIV-1/2 3.0 as the first test), were subsequently tested with Microlisa-HIV for anti-HIV antibodies. The first test missed 9 HIV reactive samples and also registered 5 false positives. The sensitivity, specificity, and negative and positive predictive values of the first test were 77.5%, 99.3%, and 98.8% and 86.1%, respectively, taking ELISA as the standard test. Our study highlights that RDTs fare poorly compared to ELISA as screening assays and that reactive results by RDTs need to be confirmed by western blot for a positive serodiagnosis of HIV infection.

Improved access to early infant diagnosis is a critical part of a child-centric prevention of mother-to-child transmission agenda

BACKGROUND

Prevention-of-mother-to-child-transmission (PMTCT) programs have made it possible to achieve dramatic reductions in the rate of vertical HIV transmission. However, high attrition, particularly after delivery, has limited the impact of these interventions for HIV-exposed infants who remain at risk through the end of breastfeeding.

DESIGN AND METHODS

A review of current literature on early infant diagnosis (EID) testing and country experience in low-and middle-income countries.

RESULTS

While PMTCT programs report reduced rates of infection among infants tested at 2 months of age, too few services are focused on retention of HIV-exposed infants in care. An unacceptably large proportion of HIV-exposed and HIV-infected infants remain unidentified. While the complexities of EID have been simplified with the development of optimized commodities and tools to improve service delivery, the inaccessibility and inadequate uptake of EID services has resulted in lag of care for the millions of HIV-exposed infants who remain unidentified. Coverage of EID testing remains low and there are many HIV- infected infants or at risk of infection who may not enter the health system through PMTCT programs. Waiting for HIV-infected children to present sick is not an adequate strategy for identifying and linking infants to treatment. Several interventions suggest a potential to expand access to EID testing, while more aggressive testing strategies may ensure children can be captured at any point of contact with the health system.

CONCLUSIONS

Programs focused on preventing vertical transmission need to increase their commitment to child-centric interventions and broaden their measure of success to reflect infants who test negative at the end of the exposure period. This paper argues that EID is a key strategy to retaining HIV-exposed infants through the end of the exposure period, as it provides an opportunity to offer early clinical care and continuous follow up. It is imperative that maternal and child survival programs become sensitized to the urgency of early identification of HIV in infants and their retention in care.

False-negative post-18-month confirmatory HIV tests in HIV DNA PCR-positive children: a retrospective analysis

OBJECTIVE

The WHO guidelines for children less than 18 months old diagnosed with HIV based on presumptive clinical diagnosis or one virologic test recommend confirmatory HIV antibody testing after 18 months of age. This study describes post-18-month HIV test results following this WHO-recommended confirmatory testing strategy.

DESIGN

Case series and retrospective review of routine program data.

METHODS

Children enrolled at the Baylor Children's Clinical Center of Excellence, a pediatric and family HIV clinic in Maseru, Lesotho from December 2005 through January 2009 with a positive HIV DNA PCR at less than 18 months of age and HIV rapid test results after 18 months of age were included. Post-18-month confirmatory HIV test results are described. Factors associated with non-positive confirmatory rapid tests were determined using binary logistic regression.

RESULTS

Of the 109 children meeting inclusion criteria, 22 (20.2%) had negative and 27 (24.8%) discordant confirmatory rapid tests. Forty-six of these 49 were on antiretroviral therapy (ART). Among these 49, 11 of 24 post-18-month HIV DNA PCRs were negative, whereas nine of 10 post-18-month HIV ELISAs were positive; 29 were definitively and 17 probably HIV-infected, two were uninfected, and one had undetermined status. Only age less than 9 months at ART initiation (odds ratio 4.25, P = 0.002) was associated with non-positive rapid tests.

CONCLUSION

False-negative post-18-month confirmatory rapid tests and HIV DNA PCRs in children on ART are common, associated with early ART initiation, and may lead to inappropriate ART discontinuation and discharge from care of truly HIV-infected children.

Utility of rapid antibody tests to exclude HIV-1 infection among infants and children aged <18 months in a low-resource setting

BACKGROUND

Excluding HIV infection among infants and young children in resource-poor settings where nucleic acid amplification tests (NAAT) are not routinely available remains a considerable challenge.

OBJECTIVES

To assess the performance of two rapid HIV antibody tests (RT) used alone and in parallel for excluding HIV infection among acutely ill infants and children <18 months in comparison to NAAT in a region where maternal HIV prevalence was approximately 7%.

STUDY DESIGN

Infants and children ≥2<18 months admitted to hospital with an acute febrile illness had two rapid antibody tests in parallel, with single and parallel results subsequently compared against NAAT.

RESULTS

HIV prevalence among 1602 enrolled infants was 3.4%. All 1526 infants with 2 negative RT were HIV negative by NAAT. All 46 infants with 2 positive RT were HIV positive by NAAT. The overall specificity of two rapid tests for excluding HIV infection was 99.5%. Sensitivity and specificity were ≥99% and >98%, respectively, across all age brackets ≥2<18 months. Overall sensitivity and specificity for a single RT was 98.2% and 99%, respectively, for Determine, and 85.5% and 99.6%, respectively, for Capillus.

CONCLUSIONS

In a setting with a maternal HIV prevalence rate of <10%, a single negative RT had excellent specificity and two negative RT performed in parallel had a perfect negative predictive value for HIV infection among acutely ill patients <18 months of age. In this and similar settings, RT could assist with excluding HIV infection with much lower complexity and cost than NAAT.

Low specificity of determine HIV1/2 RDT using whole blood in south west Tanzania

Objective

To evaluate the diagnostic performance of two rapid detection tests (RDTs) for HIV 1/2 in plasma and in whole blood samples.

Methods

More than 15,000 study subjects above the age of two years participated in two rounds of a cohort study to determine the prevalence of HIV. HIV testing was performed using the Determine HIV 1/2 test (Abbott) in the first (2006/2007) and the HIV 1/2 STAT-PAK Dipstick Assay (Chembio) in the second round (2007/2008) of the survey. Positive results were classified into faint and strong bands depending on the visual appearance of the test strip and confirmed by ELISA and Western blot.

Results

The sensitivity and specificity of the Determine RDT were 100% (95% confidence interval  = 86.8 to 100%) and 96.8% (95.9 to 97.6%) in whole blood and 100% (99.7 to 100%) and 97.9% (97.6 to 98.1%) in plasma respectively. Specificity was highly dependent on the tested sample type: when using whole blood, 67.1% of positive results were false positive, as opposed to 17.4% in plasma. Test strips with only faint positive bands were more often false positive than strips showing strong bands and were more common in whole blood than in plasma. Evaluation of the STAT-PAK RDT in plasma during the second year resulted in a sensitivity of 99.7% (99.1 to 99.9%) and a specificity of 99.3% (99.1 to 99.4%) with 6.9% of the positive results being false.

Conclusions

Our study shows that the Determine HIV 1/2 strip test with its high sensitivity is an excellent tool to screen for HIV infection, but that – at least in our setting – it can not be recommended as a confirmatory test in VCT campaigns where whole blood is used.

The performance of 5 rapid HIV tests using whole blood in infants and children: selecting a test to achieve the clinical objective

BACKGROUND

Rapid tests have the potential to improve the identification of HIV-infected children in resource-limited settings. However, they remain underutilized because of a lack of data on their performance in the field using whole blood specimens. This study aimed to assess the accuracy of rapid tests for detecting HIV exposure, excluding HIV infection in HIV-exposed infants, and diagnosing HIV infection in children older than 18 months of age.

METHODS

Five rapid tests (First Response, Pareekshak, Determine, Smart Check, and Insti) were performed using whole blood from children enrolled in a multisite, cross-sectional study in South Africa. HIV enzyme-linked immunosorbent assay and DNA polymerase chain reaction results defined HIV exposure and infection, respectively, and were the standards used for comparison.

RESULTS

Of the 851 children enrolled, 186 (21.9%) were infected with HIV. For detecting HIV exposure, Determine demonstrated the highest sensitivity of 99.3% (95% confidence interval, 98.0-99.8) in early infancy, but sensitivity declined with age as seroreversion occurred. After 8 months of age, all tests except First Response excluded HIV infection in 82% to 100% of HIV-uninfected infants and, in conjunction with a clinical assessment, did not miss any HIV-infected children. Insti was the only test that detected all HIV-infected infants, albeit on the smallest number of samples. The performance of all rapid tests in children older than 18 months of age was similar to that in adults.

CONCLUSIONS

Determine was the only rapid test that had a high enough sensitivity for detecting HIV exposure in early infancy, but it identified seroreversion later in life than the other tests. Insti warrants further investigation for both indications.

Screening for acute HIV infection in South Africa: finding acute and chronic disease

BACKGROUND

The yield of screening for acute HIV infection among general medical patients in resource-scarce settings remains unclear. Our objective was to evaluate the strategy of using pooled HIV plasma RNA to diagnose acute HIV infection in patients with negative or discordant rapid HIV antibody tests in Durban, South Africa.

METHODS

We prospectively enrolled patients with negative or discordant rapid HIV antibody tests from a routine HIV screening programme in an out-patient department in Durban with an HIV prevalence of 48%. Study participants underwent venipuncture for pooled qualitative HIV RNA, and, if this was positive, quantitative RNA, enzyme immunoassay and Western blot (WB). Patients with negative or indeterminate WB and positive quantitative HIV RNA were considered acutely infected. Those with chronic infection (positive RNA and WB) despite negative or discordant rapid HIV tests were considered to have had false negative rapid antibody tests.

RESULTS

Nine hundred and ninety-four participants were enrolled with either negative (n=976) or discordant (n=18) rapid test results. Eleven [1.1%; 95% confidence interval (CI) 0.6-2.0%] had acute HIV infection, and an additional 20 (2.0%; 95% CI 1.3-3.1%) had chronic HIV infection (false negative rapid test).

CONCLUSIONS

One per cent of out-patients with negative or discordant rapid HIV tests in Durban, South Africa had acute HIV infection readily detectable through pooled serum HIV RNA screening. Pooled RNA testing also identified an additional 2% of patients with chronic HIV infection. HIV RNA screening has the potential to identify both acute and chronic HIV infections that are otherwise missed by standard HIV testing algorithms.

Integrating HIV screening into routine health care in resource-limited settings

The United Nations is committed to achieving universal access to human immunodeficiency virus (HIV) care, treatment, and prevention. Although the gateway to HIV care and secondary prevention is knowledge of serostatus, use of voluntary counseling and testing in resource-limited settings with the highest burden of HIV infection and AIDS has been limited. On the basis of evidence of increased patient uptake and the opportunity to avoid missed HIV testing opportunities in health care facilities, in 2007, the World Health Organization recommended provider-initiated HIV testing as a standard part of medical care in settings with generalized HIV epidemics. Although provider-initiated testing has shown promise, optimal implementation strategies that ensure broad coverage, while preserving human rights, remain an active area of research. We review the benefits of knowledge of HIV serostatus and evidence from multiple countries surrounding the successes and pitfalls of provider-initiated testing in health care and home-based settings.

Cost-effectiveness of routine rapid human immunodeficiency virus antibody testing before DNA-PCR testing for early diagnosis of infants in resource-limited settings

BACKGROUND

Infants born to HIV-infected women should receive HIV testing to allow early diagnosis and treatment. Recommendations for resource-limited settings stress laboratory-based virologic assays. While effective, these tests are logistically complex and expensive. This study explored the cost-effectiveness of incorporating initial screening with rapid HIV tests (RHT) into the conventional testing algorithm to screen-out HIV-uninfected infants, thereby reducing the need for costly virologic testing.

METHODS

Data on HIV prevalence, RHT sensitivity and specificity, and costs were collected from 820 HIV-exposed children (1.5-18 months) attending 2 postnatal screening programs in Uganda during July 2005 to December 2006. Cost-effectiveness models compared the conventional testing algorithm DNA polymerase chain reaction (DNA-PCR with Roche Amplicor v1.5) with a modified algorithm (initial RHT to screen-out HIV-uninfected infants before DNA-PCR).

RESULTS

The model estimated that the conventional algorithm would identify 94.3% (91.8%-94.7%) of HIV-infected infants, compared with 87.8% (79.4%-90.5%) for a modified algorithm using RHT (HIV 1/2 Determine) and excluding the need for DNA-PCR for HIV antibody-negative infants. Costs per infant were $23.47 ($23.32-$23.76) for the conventional algorithm and between $22.75 ($21.89-$23.31) and $7.58 ($6.41-$10.75) for the modified algorithm, depending on infant age and symptoms. Compared with the conventional algorithm, costs per HIV-infected infant identified using the modified algorithm were higher in 1.5-to 3-month-old infants, but significantly lower in 3-month-old and older infants. Models replicating the whole infant testing program showed the modified algorithm would have marginally lower sensitivity, but would reduce total program costs by 27% to 40%, producing an incremental cost-effectiveness ratio of $1489 ($686-$6781) for the conventional versus modified algorithms.

CONCLUSIONS

Screening infants with RHT before DNA-PCR is cost-effective in infants 3 months old or older. Incorporating RHT into early infant testing programs could improve cost-effectiveness and reduce program costs.

Failure of human immunodeficiency virus enzyme immunoassay to rule out infection among polymerase chain reaction-negative Vietnamese infants at 12 months of age

BACKGROUND

: Previous studies have demonstrated that >90% of HIV-uninfected infants serorevert, as seen in the results of enzyme immunoassay (EIA) testing by 12 months of age, making it feasible to confirm or rule out infection. We assessed the reliability of EIA in a cohort of Vietnamese infants.

METHODS

: HIV-exposed, uninfected infants enrolled in a parent diagnostic and monitoring study from February 2005 through August 2006 were eligible for inclusion in a prospective cohort study of HIV-EIA performance. Testing using 2 standard assays (Genscreen HIV 1/2 version 2, Bio-Rad; Murex 1.2.0, Murex Biotech) was initiated at 12 months of age. Infants were categorized as EIA-negative (seroreverted; negative Genscreen), EIA-indeterminate (positive Genscreen, negative Murex), or EIA-positive (Genscreen and Murex positive).

RESULTS

: Of 273 infants included in the study, 59 (22%) were EIA-negative at 12 months, 131 (48%) were indeterminate, and 83 (30%) were EIA-positive; specificity 21.6 (95% confidence interval: 16.6, 26.3). Infants with positive EIAs at 12 months were 74% more likely than EIA-indeterminate infants to test indeterminate or positive at 18 months (risk ratio, 1.74, 95% confidence interval: 1.15, 2.64; P = 0.03).

CONCLUSIONS

: Expectations regarding infant seroreversion by standard EIAs should be reassessed to reflect potential cross-regional differences in their performance.

Suitability of simple human immunodeficiency virus rapid tests in clinical trials in community-based clinic settings

The suitability and accuracy of using simple human immunodeficiency virus (HIV) rapid (SR) tests in community-based clinics in northwest Tanzania were determined to assess eligibility for participation in clinical trials. The HIV rapid and ELISA test results for 789 women aged 16 to 54 who were screened for two clinical trials of HIV prevention were compared. Women were offered voluntary HIV counseling and testing (VCT) at screening; those who accepted were tested with the Abbott Determine and Trinity Biotech Capillus SR tests in parallel. The results were confirmed by two parallel HIV enzyme-linked immunosorbent assay (ELISA) tests (Abbott Murex HIV Ag/Ab combination and Vironostika Uniform II HIV Ag/Ab) to determine eligibility. Positive samples for any of the four assays were confirmed by a line immunoassay and p24 testing. The parallel SR tests had high concordance (96.2%) with the parallel ELISA algorithm. The sensitivities of the SR tests were 98.6% for Capillus (95% confidence interval [CI], 95.1 to 99.8%), 99.3% for Determine (95% CI, 96.2 to 100%), and 98.6% for the parallel SR (95% CI, 95.1 to 99.8%). The specificities were 99.7% for Capillus (95% CI, 98.9 to 100%), 99.7% for Determine (95% CI, 98.9 to 100%), and 100% for the parallel SR (95% CI, 99.4 to 100%). SR tests are suitable for use in community-based clinical research settings to assess eligibility both for trial participation and for the provision of on-site VCT services.

Evaluation of seven rapid HIV tests to detect HIV-exposure and seroreversion during infancy

BACKGROUND

Failure to determine the HIV status of all pregnant women impedes progress in preventing and treating paediatric HIV because vertically exposed infants are not identified for prophylaxis, early HIV diagnosis and care.

OBJECTIVES

To assess the performance of rapid HIV tests in comparison to a laboratory-based HIV ELISA test for determining HIV-exposure and excluding HIV infection during infancy.

STUDY DESIGN

Seven rapid HIV tests were evaluated on 2266 stored samples from 116 HIV-exposed infants of known HIV status at four ages during infancy. The HIV ELISA for each sample was the standard against which rapid results were assessed to establish HIV-exposure.

RESULTS

Rapid tests did not perform uniformly during infancy. For detecting HIV-exposure the sensitivity of most rapid tests to 3 months of age approached that of an HIV ELISA however only Determine maintained this sensitivity (99.7%) throughout infancy. For excluding HIV infection (i.e. for correctly identifying HIV-uninfected infants) the specificity of all rapid tests except Determine exceeded that of the HIV ELISA from 7 months of age.

CONCLUSIONS

The use of rapid tests in infancy could improve identification and care of HIV-exposed infants. Further evaluation under field conditions is required before rapid tests can be incorporated into evidence-based diagnostic algorithms.