Low specificity of the Murex fourth-generation HIV enzyme immunoassay in Tanzanian adolescents

False reactive HIV-1 diagnostic test results in an individual from Kenya on multiple testing platforms-A case report

Background

Rapid diagnostic tests (RDT) are routinely used in screening for HIV infection. More complex diagnostic algorithms incorporating fourth-generation screening and confirmatory HIV-1/HIV-2 differentiation immunoassays (IA) may be used to confirm HIV infection. Co-infections and autoimmune diseases may lead to falsely reactive HIV diagnostic test results.

Case presentation

A Kenyan man with asymptomatic schistosomiasis and low risk factors for HIV infection demonstrated an inconsistent and discordant pattern of reactivity on HIV RDT, repeated reactivity on fourth-generation IA and positive at a single time-point for HIV-1 on the Geenius HIV1/HIV2 confirmatory assay during the course of a prospective cohort study with HIV repeat testing. The individual initiated antiretroviral therapy following HIV diagnosis. However, his bi-annual behavioral questionnaire suggested low-risk factors for infection. Supplementary confirmatory serologic and nucleic acid tests were performed and gave discordant results. The participant was determined to be HIV uninfected using cell-associated HIV-1 DNA/RNA testing and antiretroviral therapy was discontinued.

Discussion and conclusions

Sole reliance on diagnostic test results may result in misdiagnosis of HIV infection, social harm and potential antiretroviral induced drug toxicity. Interpretation of HIV test results should incorporate multiple parameters.

Comparison of two immunoassays for concurrent detection of HCV antigen and antibodies among HIV/HCV co-infected patients in dried serum/plasma spots

Hepatitis C virus (HCV) antigen/antibody (Ag/Ab) assays offer the benefit of reducing the window period compared to assays that detect only HCV-Ab. In this study the performance of the Murex Ag/Ab (Murex, Abbott) and Monolisa Ag/Ab Ultra (Monolisa, Bio-Rad) ELISAs was compared for the use of filter dried serum/plasma spots (DS/PS) with a focus on the sensitivity and the percentage of correct positive test results. Correct positive ELISA results were assumed for samples that subsequently tested positive for HCV RNA by RT-qPCR, or RNA negative samples that tested positive in a Western blot (confirmed ELISA results). Sensitivity was evaluated from DS/PS eluates using HCV seroconversion panels [plasma samples of subtypes-(St) 1a, 2b)] and longitudinal HCV antibody positive serum panels (St 1b, 2b, 3a, and 4d). The proportion of correct positive test results was evaluated using 1102 newly diagnosed HIV positive clinical dried serum spots (DSS) eluates for screening of potential HCV co-infection. For the plasma HCV seroconversion samples, which were used as a reference for DSS eluates, the Murex became reactive earlier for antigen positive bleeds. However, for the HCV antibody positive eluates and dilutions thereof, the Monolisa demonstrated a superior sensitivity. Of the clinical DSS 22.8 % (28/123) of samples reactive in the Murex were negative in a subsequent RT-qPCR and Western blot, while only 1.9 % (2/105) of the samples reactive in the Monolisa were negative in these confirmatory assays. Our results indicate that the Monolisa provides fewer false positive results for HCV detection in DSS, whereas for undiluted plasma or serum samples, the Murex can serve as an additional diagnostic tool to narrow the window period.

HIV infection in Xi'an, China: epidemic characterization, risk factors to false positives and potential utility of the sample-to-cutoff index to identify true positives using Architect HIV Ag/Ab combo

Background

In China, although tremendous efforts has been made, the HIV/AIDS is still not controlled.

Objectives

The study was carried out to determine the epidemic of HIV infection in Xi'an, analyse false positives (FP) risk factors and potential utility of sample-to-cutoff index to identify true positives using Architect HIV Ag/Ab Combo.

Methods

A retrospective review for HIV screening by Architect HIV Ag/Ab Combo was performed in a teaching hospital in Xi'an between 2015 and 2016. The prevalence of HIV, positive predictive value (PPV) at different cut-off indexices (COI) were calculated. The epidemic of infections and risk factors for FP results were investigated.

Results

In the study, the HIV prevalence and FP rate of Architect HIV Ag/Ab Combo were 0.076 and 46.08%, respectively. The Han Chinese, males and people aged < 40 years accounted for the majority of infections (98.29, 76.07 and 73.5%, respectively). 85.47% of the infections were transmitted through sexual contact (35.04% of male homosexual and 50.43% of heterosexual). COI at 1-10, 10-30 and ≥ 30, the PPVs were 0, 50 and 100%, respectively. The independent risk factors for FP, i.e., pregnancy and malignancy had a statistically significant association with FP (p < 0.05), and age had a very strong statistically significant association with FP (p < 0.001).

Conclusions

In Xi'an, sexual contact was the most important transmission mode for HIV, and the infections were predominantly identified in Han Chinese, males, young and middle-aged people. For Architect HIV Ag/Ab Combo, it can achieve 100% of PPV with COI ≥30, and the age was strongly statistically associated with FP.

The characteristics of screening and confirmatory test results for HIV in Xi'an, China

OBJECTIVES

Individuals with recent or acute HIV infection are more infectious than those with established infection. Our objective was to analyze the characteristics of detection among HIV infections in Xi'an.

METHODS

A 4th-generation kit (Architect HIV Ag/Ab Combo) and three 3rd-generationEIA kits (WanTai, XinChuang and Livzon) were used for HIV screening. Overall, 665 individuals were identified as positive and were tested by western blotting (WB). The characteristics of the screening and confirmatory tests were analyzed, including the band patterns, the early detection performance and the false-positive rates.

RESULTS

In total, 561 of the 665 patients were confirmed as having HIV-1 infection, and no HIV-2 specific band was observed. Among these 561 WB-positive cases, reactivity to greater than or equal to 9 antigens was the most commonly observed pattern (83.18%), and the absence of reactivity to p17, p31 and gp41 was detected in 6.44%, 5.9% and 2.86% of the cases, respectively. Two cases were positive by the 4th-generation assay but negative by the 3rd-generation assay for HIV screening and had seroconversion. The false-positive rate of the Architect HIV Ag/Ab Combo (22.01%) was significantly higher than those of WanTai (9.88%), XinChuang (10.87%) and Livzon (8.93%), p<0.05.

CONCLUSION

HIV infection in Xi'an is mainly caused by HIV-1, and individuals are rarely identified at the early phase. Although the false-positive rate of the 4th-generation assay was higher than that of the 3rd-generation assay, it is still recommended for use as the initial HIV screening test for high-risk individuals. In Xi'an, a 3rd-generation assay for screening could be considered.

Self-reported HIV-positive status but subsequent HIV-negative test result using rapid diagnostic testing algorithms among seven sub-Saharan African military populations

HIV rapid diagnostic tests (RDTs) combined in an algorithm are the current standard for HIV diagnosis in many sub-Saharan African countries, and extensive laboratory testing has confirmed HIV RDTs have excellent sensitivity and specificity. However, false-positive RDT algorithm results have been reported due to a variety of factors, such as suboptimal quality assurance procedures and inaccurate interpretation of results. We conducted HIV serosurveys in seven sub-Saharan African military populations and recorded the frequency of personnel self-reporting HIV positivity, but subsequently testing HIV-negative during the serosurvey. The frequency of individuals who reported they were HIV-positive but subsequently tested HIV-negative using RDT algorithms ranged from 3.3 to 91.1%, suggesting significant rates of prior false-positive HIV RDT algorithm results, which should be confirmed using biological testing across time in future studies. Simple measures could substantially reduce false-positive results, such as greater adherence to quality assurance guidelines and prevalence-specific HIV testing algorithms as described in the World Health Organization’s HIV testing guidelines. Other measures to improve RDT algorithm specificity include classifying individuals with weakly positive test lines as HIV indeterminate and retesting. While expansion of HIV testing in resource-limited countries is critical to identifying HIV-infected individuals for appropriate care and treatment, careful attention to potential causes of false HIV-positive results are needed to prevent the significant medical, psychological, and fiscal costs resulting from individuals receiving a false-positive HIV diagnosis.

The trade-off between accuracy and accessibility of syphilis screening assays

The availability of rapid and sensitive methods to diagnose syphilis facilitates screening of pregnant women, which is one of the most cost-effective health interventions available. We have evaluated two screening methods in Tanzania: an enzyme immunoassay (EIA), and a point-of-care test (POCT). We evaluated the performance of each test against the Treponema pallidum particle agglutination assay (TPPA) as the reference method, and the accessibility of testing in a rural district of Tanzania. The POCT was performed in the clinic on whole blood, while the other assays were performed on plasma in the laboratory. Samples were also tested by the rapid plasma Reagin (RPR) test. With TPPA as reference assay, the sensitivity and specificity of EIA were 95.3% and 97.8%, and of the POCT were 59.6% and 99.4% respectively. The sensitivity of the POCT and EIA for active syphilis cases (TPPA positive and RPR titer ≥ 1/8) were 82% and 100% respectively. Only 15% of antenatal clinic attenders in this district visited a health facility with a laboratory capable of performing the EIA. Although it is less sensitive than EIA, its greater accessibility, and the fact that treatment can be given on the same day, means that the use of POCT would result in a higher proportion of women with syphilis receiving treatment than with the EIA in this district of Tanzania.

Field evaluation of the Abbott ARCHITECT HIV Ag/Ab Combo immunoassay

BACKGROUND

Fourth generation assays for HIV diagnosis are progressively being introduced into routine services, due to their improvement of diagnosis. In spite of this, HIV diagnosis remains a challenge in sub-Saharan Africa, due to false positive reactivity. There is a continuous need for field evaluations and routine validations of fourth generation HIV tests in African populations.

OBJECTIVES

Evaluate the performances of the ARCHITECT HIV Ag/Ab kit (Abbott) in a population living in an African setting-Cameroon compared to a population living in a European setting-France.

STUDY DESIGN

645 HIV samples from both France and Cameroon were evaluated. The positive panel (378 samples) included a diverse series of HIV-1 variants (groups M, N, O, and P) as well as HIV-2 samples. Results were compared to original diagnosis done with other 4th generation assays (AxSYM HIV Ag/Ab (Abbott) and Vidas HIV DUO QUICK) (bioMérieux).

RESULTS

Sensitivity of the ARCHITECT was 100% in both sites. It diagnosed all variants of the panel with different reactivity profiles following strain diversity. A wider range of reactivity was observed for group O. Specificity was slightly lower (97.6%) in Cameroon than in France (98.6%), probably due to a higher rate of false positive reactivity. ARCHITECT HIV Ag/Ab assay had high performances in clinical sensitivity and specificity and is adapted to the wide genetic diversity of viruses circulating in West Central Africa.

CONCLUSION

Our results further highlight the need to evaluate HIV diagnostic tests before introduction into routine diagnostic services both in the North and in the South.

Performance of six commercial enzyme immunoassays and two alternative HIV-testing algorithms for the diagnosis of HIV-1 infection in Kisumu, Western Kenya

Performances of serological parallel and serial testing algorithms were analyzed using a combination of three ELISA and three rapid tests for the confirmation of HIV infection. Each was assessed individually for their sensitivity and specificity on a blinded panel of 769 retrospective sera of known HIV status. Western blot was used as a confirmatory assay for discordant results. Subsequently, one parallel and one serial testing algorithm were assessed on a new panel of 912 HIV-positive and negative samples. Individual evaluation of the ELISAs and rapid tests indicated a sensitivity of 100% for all assays except Uni-Gold with 99.7%. The specificities ranged from 99.1% to 99.4% for rapid assays and from 97.5% to 99.1% for ELISAs. A parallel and serial testing algorithms using Enzygnost and Vironostika, and Determine followed by Uni-Gold respectively, showed 100% sensitivity and specificity. The cost for testing 912 samples was US$4.74 and US$ 1.9 per sample in parallel and serial testing respectively. Parallel or serial testing algorithm yielded a sensitivity and specificity of 100%. This alternative algorithm is reliable and reduces the occurrence of both false negatives and positives. The serial testing algorithm was more cost effective for diagnosing HIV infections in this population.

Association of schistosomiasis with false-positive HIV test results in an African adolescent population

This study was designed to investigate the factors associated with the high rate of false-positive test results observed with the 4th-generation Murex HIV Ag/Ab Combination EIA (enzyme immunoassay) within an adolescent and young-adult cohort in northwest Tanzania. (4th-generation assays by definition detect both HIV antigen and antibody.) The clinical and sociodemographic factors associated with false-positive HIV results were analyzed for 6,940 Tanzanian adolescents and young adults. A subsample of 284 Murex assay-negative and 240 false-positive serum samples were analyzed for immunological factors, including IgG antibodies to malaria and schistosoma parasites, heterophile antibodies, and rheumatoid factor (RF) titers. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). False-positive HIV test results were associated with evidence of other infections. False positivity was strongly associated with increasing levels of Schistosoma haematobium worm IgG1, with adolescents with optical densities in the top quartile being at the highest risk (adjusted OR=40.7, 95% CI=8.5 to 194.2 compared with the risk for those in the bottom quartile). False positivity was also significantly associated with increasing S. mansoni egg IgG1 titers and RF titers of >or=80 (adjusted OR=8.2, 95% CI=2.8 to 24.3). There was a significant negative association between Murex assay false positivity and the levels of S. mansoni worm IgG1 and IgG2 and Plasmodium falciparum IgG1 and IgG4. In Africa, endemic infections may affect the specificities of immunoassays for HIV infection. Caution should be used when the results of 4th-generation HIV test results are interpreted for African adolescent populations.

Immunoassays for the diagnosis of HIV: meeting future needs by enhancing the quality of testing

Immunoassays for detecting HIV infection perform better than other serological assays. HIV immunoassays are presented in a number of different formats: instrument-based, plate, rapid assays and as immunoblots. HIV immunoassays for screening and diagnosis are now in their fourth generation; an assay generation meaning that significant modifications to the assay format have led to a significant enhancement in quality. Although still not perfect, they are now of exceptionally high quality if conducted properly. Most problems relate to how the assays are performed. Many laboratories, especially in high human development index (HDI) countries, manage testing within functioning quality-management systems, but this is not true of laboratories in low HDI countries or in many medium HDI countries. Simple rapid tests for HIV are being used increasingly, and create special challenges for assuring quality. Users of HIV immunoassays are learning that a poorer assay used well has better outcomes than a splendid assay performed poorly. Experience highlights the importance of conducting HIV testing within quality-managed systems and according to international standards, but testing quality and laboratory quality management must be funded adequately.

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.