Large-scale evaluation of an alternative strategy for confirmation of HIV antibodies

False positive viral marker results in blood donors and their unintended consequences

False positive (FP) viral marker results in blood donors continue to pose many challenges. Informing donors of FP results and subsequent deferral can result in stress and anxiety for donors and additional complexity and workload for blood services. Donor management strategies need to balance the requirement to minimise donor anxiety and inconvenience while maintaining sufficiency of supply. Decisions about how and when to inform donors of FP results and determine deferral periods can be difficult as FP results, while often transitory, can take up to several years to resolve. Additional complexities include the interpretation of indeterminate serological confirmatory testing without detectable viral RNA or non-discriminated NAT results with concomitant anti-HBc reactivity - both may be due to FP results, but the former may also represent past infection and the later may represent occult hepatitis B infection. In this review we discuss strategies to minimise indeterminate serological confirmatory results, possible donor deferral policies and the impact on donors when notified of FP results. We also provide some new data from Australia that address the challenge of interpreting non-discriminated NAT results with concomitant anti-HBc reactivity. Ultimately, the challenge is for each blood service to develop appropriate strategies for donor management, taking into account local information and requirements.

Can we improve the management of blood donors with nonspecific reactivity in viral screening and confirmatory assays?

Donors with nonspecific reactivity in viral screening or confirmatory assays are problematic for blood services because of donor management issues and product loss. Considerable experience has now accumulated in the use of screening and confirmatory assays; therefore, it is timely to examine the ways in which donors with nonspecific reactivity are managed. In this review, we summarize the causes and characteristics of nonspecific reactivity in blood donors and approaches for reducing the number of nonspecific reactive results and we offer some suggestions for improving the management of these donors.

Evaluation of rapid HIV testing strategies in under equipped laboratories in the Central African Republic

Voluntary testing is described as being cornerstone to impact the spread of human immunodeficiency virus (HIV) infection if the person who tests positive is counseled. Therefore, simple, accurate and affordable diagnostic tests are required. The immunoblot test used in developed countries is too expensive for large-scale use in developing countries. Therefore, alternative strategies must be developed. A strategy based on two consecutive rapid tests was tested. This strategy used the Determine HIV-1/2 (Abbott Laboratories, Tokyo, Japan) rapid immunochromatographic test as a screening test and the Uni-Gold HIV test (Trinity Biotech, Dublin, Ireland), SDHO HIV 1/2 test (SDHO laboratories, Saint-Sauveur des Monts, Canada), HIV 1/2 Quick test (Cypress Diagnostics, Langdorp, Belgium) or Retrocheck HIV test (Qualpro Diagnostics, Goa, India) as a confirmatory test. Reference serum samples (HIV-positive and HIV-negative) were first used to evaluate the four confirmatory tests. Secondly, 159 serum samples were used to compare the "consecutive" testing strategy used in our laboratory with the two-test strategy. Thirdly, we tested the feasibility of using this two-test strategy in a under equipped laboratory. The sensitivity and negative predictive value of both test strategies were 100%. The specificity and positive predictive value of the four confirmatory tests were similar (>98%). The strategy used in our laboratory and the two-test strategy always gave identical results, regardless of where this strategy was performed (Institut Pasteur de Bangui or M'baïki hospital). This new strategy appears to be reliable, simple, feasible and rapid in under equipped laboratories. It allows counseling and results to be given on the same day, which should improve post-test counseling.

A simple semi-rapid HIV-1&2 confirmatory immunoassay using magnetic particles

The Bionor HIV-1&2 Confirmatory Test is a semi-rapid simple immunoassay based on magnetic particles for the confirmation of serological status to human immunodeficiency virus (HIV). The specificity and sensitivity of this assay was evaluated by comparison with the Diagnostic Biotechnology HIV-1 Western blot (WB) 2.2 and the HIV-2/SBL-6669 WB. Bionor's confirmatory test demonstrated 98% specificity when testing sero-negative blood donors and false positive sera in screening tests compared to 81.5 and 71.6%, respectively, using the HIV-1 WB. The sensitivity of this assay for HIV-1 antibody positive sera was 97.9% compared to the WB which was 99.5%. When testing confirmed HIV-2 antibody positive samples, 2/100 scored negative using this confirmatory test similar to other HIV-2 peptide-based line immunoassays available commercially, whilst 8/100 were indeterminate reacting to HIV-2 membrane antigens only. Bionor's confirmatory test detected HIV-1 seropositivity earlier than the WB in longitudinal seroconversion panels and could discriminate between HIV-1 and -2 infection. The number of indeterminate responses was generally reduced significantly using Bionor's confirmatory test compared to the HIV-1 WB. The greater specificity, speed and ease of interpretation of Bionor's confirmatory test renders it an attractive and cost effective alternative to the WB for confirming HIV serological status worldwide.

Advantages of an alternative strategy based on consecutive HIV serological tests for detection of HIV antibodies in Central African Republic

Voluntary testing and counselling are accepted widely for the prevention of human immunodeficiency virus (HIV) infection. Therefore, simple, accurate and affordable tests are required. The diagnosis strategy used in developed countries, based on an immunoblot confirmatory test, cannot be used on a large scale in developing countries because of its cost. Therefore, alternative strategies must be developed. In this study, we tested according UNAIDS and World Health Organisation recommendations for HIV testing strategies, a strategy based on two consecutive tests, using the mixed automatic enzyme immunoassays test Vidas HIV DUO as a screening test and Determine Abbott rapid immunochromatographic test as a confirmatory test. In first step, reference serum samples (113 HIV-positive and 167 HIV-negative) were used to evaluate the performance of both tests. In a second step, 876 serum samples from patients were used to compare the 'simultaneous' testing strategy currently used in Central African Republic (CAR) to the 'consecutive' testing strategy. The sensitivity and negative predictive value of both tests were 100%. The specificity and positive predictive value of Determine Abbott (>99%) were higher than those of Vidas HIV DUO (90.4 and 87.6%, respectively). In all cases in which the two tests gave discrepant results, the patient was considered HIV-negative after a second test carried out 2-4 weeks later since the optical density value of the Vidas HIV DUO of the second sample was not higher than that of the first sample. This new consecutive testing strategy appears to be reliable, simple and rapid, allowing counselling and results to be given on the same day, which we believe is important for improving post-test counselling. Furthermore, the consecutive testing strategy reduces the cost of testing, which is very important in developing countries.

Strategies for diagnosis of HTLV-I and -II

BACKGROUND

No gold standard exists for diagnosis of HTLV infection. The aim of thus study was to compare the accuracy of a combination of two sensitive ELISAs with Western blot (WB), a line immunoassay, and PCR for diagnosis of HTLV infection.

STUDY DESIGN AND METHODS

Nine hundred eighty-five specimens were tested for the presence of HTLV antibodies by HTLV-I and/or HTLV-II EIAs (Murex and Ortho), WB (Diagnostic Biotechnology), line immunoassay (INNO-LIA, Innogenetics), and/or presence of HTLV DNA by PCR. The results were compared with the probable HTLV infection status of each subject, as determined by detailed review of all available laboratory, clinical, and epidemiologic data.

RESULTS

The sensitivity for diagnosis of HTLV-I infection was high for all assays evaluated, but both PCR and WB had a lower sensitivity rate (approx., 80%) for confirmation of HTLV-II. INNO-LIA detected 94 percent of the HTLV-II-positive samples. However, Murex EIA in combination with Ortho EIA was 100-percent sensitive for the detection of both HTLV-I and HTLV-II antibodies. Furthermore, the number of samples giving indeterminate results in the ELISA combination was much lower as compared with WB (2.5% vs. 50%).

CONCLUSION

Based on these findings, a new, more sensitive and specific test strategy for HTLV diagnosis than the current algorithm, which includes WB, is proposed. Thereby, both the direct and indirect costs can be substantially reduced.

The accuracy of an alternative confirmatory strategy for detection of antibodies to HIV-1: experience from a regional laboratory in Kagera, Tanzania

BACKGROUND

Constant improvement of HIV tests often results in withdrawal of poorer quality tests by the manufacturing companies. It is thus often necessary to evaluate new HIV testing kits and modify the existing testing strategies.

OBJECTIVES

To evaluate an alternative HIV antibody testing strategy which involves consecutive testing of sera by two enzyme-linked immunosorbent assays (ELISA), which both are recombinant antigen-based but utilise different test principles, followed by re-testing of sera giving discordant results.

STUDY DESIGN

Sera (n = 1558) from a cross-sectional study of the HIV-1 seroprevalence in the Kagera region of Tanzania were tested using two ELISAs in parallel: Enzygnost anti-HIV-1/2 plus and Wellcozyme HIV-1 recombinant. Western blot analysis was done on all concordantly reactive and repeatedly discordant reactive samples as well as on 10% of concordantly ELISA negative sera.

RESULTS

Two hundred and four sera (13.1%) were confirmed HIV-1-antibody positive. Both ELISAs had a sensitivity of 100%. The specificities of the ELISAs at initial and repeated testing were 99.8 and 99.9%, respectively, for Enzygnost and 97.7 and 99.5%, respectively, for Wellcozyme. None of the sera was concordantly false positive in both ELISAs. The mean ratio of the optical density of a sample to the cut off value of the test run (OD/CO ratio) was lower for samples giving false positive reactions than for confirmed HIV-1-antibody-positive samples. It is therefore important to interpret with caution HIV antibody ELISA test results on samples giving low OD/CO ratios. None of 10% of randomly selected concordantly ELISA negative sera gave a positive Western blot reaction.

CONCLUSIONS

This field evaluation of an HIV antibody testing strategy involving the use of a recombinant antigen-based sandwich ELISA (Enzygnost) followed by a recombinant antigen-based competitive ELISA (Wellcozyme) showed that it had a sensitivity and specificity of 100%.

Field evaluation of alternative testing strategies for diagnosis and differentiation of HIV-1 and HIV-2 infections in an HIV-1 and HIV-2-prevalent area

OBJECTIVE

To identify cost-efficient alternative antibody testing strategies for screening, confirmation and discrimination of HIV-1 and HIV-2 infections, including rapid simple tests (RST) as well as enzyme-linked immunosorbent assays (ELISA), in a HIV-1 and HIV-2-prevalent area.

DESIGN

Evaluation and comparison of anti-HIV-1/2 assays, adhering to the World Health Organization recommendations for alternative confirmatory strategies, using banked and prospectively collected specimens in Guinea-Bissau.

METHODS

A total of 1110 consecutive sera from Bissau were included in the first phase, of which 198 (17.8%) were HIV-seropositive: 52 (4.7%) HIV-1, 120 (10.8%) HIV-2, and 26 (2.3%) HIV-1/HIV-2 dually reactive. In addition, 95 selected HIV-positive specimens were included for study of sensitivity and cross-reactivity between HIV-1 and HIV-2. Western blot was used as a gold standard for confirming the reactivity of the specimens. All specimens were screened by two assays. Enzygnost ELISA and Capillus RST. Samples reactive by any of the screening assays were further tested by assays chosen for confirmation: UBI ELISA, Innotest ELISA Recombigen RST, Multispot RST and Immunocomb RST. The confirmatory RST as well as Wellcozyme Recombinant HIV-1 ELISA, PEPTI-LAV and INNO-LIA were also used to study differentiation between HIV-1 and HIV-2.

RESULTS

The sensitivities of all assays were 100%. The specificities of the screening assays at initial and repeated testing were 98.0 and 99.7%, respectively, for Enzygnost and 99.8 and 99.9%, respectively, for Capillus. The various combinations of two or three assays showed specificities of 99.2-100%. Several possible combinations of assays were identified where a specificity of 100% and good differentiation between HIV-1 and HIV-2 was achieved. Significant differences in the capacity to discriminate were noted; Immunocomb and PEPTI-LAV had the lowest number of dual-reactive results. A follow-up study of 1501 consecutive samples tested with the strategy chosen for routine use showed a sensitivity and specificity comparable to ELISA and Western blot.

CONCLUSION

High sensitivities and specificities were obtained with various combinations of assays including RST as well as ELISA, and these procedures are well suited for field use in Africa. Serodiagnostic strategies for HIV can be based on RST alone and differentiation between HIV-1 and HIV-2 can be achieved as part of these strategies. Large differences in the capacity of individual assays to discriminate between HIV-1 and HIV-2 were observed.