Evaluation of the Abbott ARCHITECT HIV Ag/Ab combo assay for determining recent HIV-1 infection.

BACKGROUND: Given the challenges and costs associated with implementing HIV-1 incidence assay testing, there is great interest in evaluating the use of commercial HIV diagnostic tests for determining recent HIV infection. A diagnostic test with the capability of providing reliable data for the determination of recent HIV infection without substantial modifications to the test protocol would have a significant impact on HIV surveillance. The Abbott ARCHITECT HIV Ag/Ab Combo Assay is an antigen/antibody immunoassay, which meets the criteria as the first screening test in the recommended HIV laboratory diagnostic algorithm for the United States. METHODS: In this study, we evaluated the performance characteristics of the ARCHITECT HIV Ag/Ab Combo signal-to-cutoff ratio (S/Co) for determining recent infection, including estimation of the mean duration of recent infection (MDRI) and false recent rate (FRR), and selection of recency cutoffs. RESULTS: The MDRI estimates for the S/Co recency cutoff of 400 is within the 4 to 12 months range recommended for HIV incidence assays, and the FRR rate for this cutoff was 1.5%. Additionally, ARCHITECT Combo S/Co values were compared relative to diagnostic test results from two prior prospective HIV-1 diagnostic studies in order to validate the use of the S/Co for both diagnostic and recency determination. CONCLUSION: Dual-use of the ARCHITECT Combo assay data for diagnostic and incidence purposes would reduce the need for separate HIV incidence testing and allow for monitoring of recent infection for incidence estimation and other public health applications.

The evaluation of low cut-off index values of Elecsys® HIV combi PT assay in predicting false-positive results.

OBJECTIVE: To analyze the results of different cut-off index (COI) values of Elecsys® HIV combi PT assay and to assess the role of COI in reducing the frequency of false-positive results. METHODS: We conducted a retrospective study of samples analyzed by Elecsys® HIV combi PT assay, a 4th-generation ECLIA, between 2016 and 2017. A total amount of 379 122 samples were collected for HIV (Human Immunodeficiency Virus) screening. RESULTS: A total of 379 122 samples were analyzed. 2528 (0.67%) were positive by Elecsys® HIV combi PT. Of these, 468 were false-positive results, and most of them (94.87%) were in samples with 1 < COI < 15. The false-positive rate was 0.12%. Patients with false-positive samples were more distributed in elder (P < .001) and female (P < .001) than true-positive specimens. The median COI in true-positive specimens was (385.20), which is significantly higher than false-positive specimens (2.08). The consistency between Elecsys® HIV combi PT assay and 3rd-generation and positive predictive value (PPV) increased with higher COI values. Cancer, infection, and neurological diseases were considered the potential confounding factors of HIV false-positive results (19.44%, 11.11%, and 6.62%, respectively). CONCLUSION: Samples with low COI values, especially those contain confounding factors, need to be further scrutinized to determine whether the confounding factors may cause false-positive problem. In addition, the hypothesis that low COI values may predict false-positive results is valid.

Utility of grey zone testing strategy in transfusion transmissible infection testing in blood bank is of limited value!

Several blood banks use grey zone (GZ) phenomenon (defined as samples with optical density within 10% below the cut off in enzyme immuno-assay [EIA]/chemiluminescence immunoassay [CLIA]) to further augment blood safety. There is paucity of data regarding usefulness of GZ sample and its application in Transfusion Transmissible Infection (TTI) screening procedures in blood transfusion services. We looked at our GZ sample results and their confirmatory test results to verify if it adds to blood safety in our set-up? We performed a prospective analytical study on blood donors' samples over two years. All the donors' samples were screened for TTI using CLIA. Samples with signal/cut-off ratio between ≥0.90 and <1.00 were classified under GZ. They were re-tested in duplicate and submitted to confirmatory testing: Neutralization Test for HBsAg, Immunoblot for HCV, and Western blot for HIV. Among the 50,064 blood donors donating the blood during study period, 573 (1.14%) donors were reactive for HBsAg, HCV, and HIV. Forty-seven (0.1%) TTI samples were GZ, but none was "confirmed positive." The utility of GZ testing seems to be limited. However, this may be continued for sake of "erring on the side of caution" and since this only results in negligible wastage (0.1%) of blood units.

Architect i2000 SR has improved turnaround time for infectious disease serology testing over Vitros ECiQ.

BACKGROUND: Vitros ECiQ and Architect i2000 SR are two automated instruments used to detect serology biomarkers of hepatitis A, B and C viruses, and HIV infections. We compared performance of the Architect to the Vitro EciQ after implementation at our institution. METHODS: A retrospective review was performed to compare patient samples tested on the Vitros ECiQ or Architect for hepatitis and HIV serological assays. The positivity rate, frequency of equivocal results, turnaround times (TAT), and hands-on time (HOT) were analyzed. RESULTS: There was no statistical difference in the positivity rate between the two instruments, with the exception of two assays. An increase in equivocal results was observed for the Architect (0.2% vs 0.5%). Notably, the TAT for the Architect i2000 was shorter for all except one assay (31.6 vs 33.7 hours) and demonstrated improved workflow. CONCLUSIONS: Overall, both instruments performed comparably. Architect had shorter TAT over Vitros.

Rapid Testing Algorithm Performance in a Low-Prevalence Environment.

BACKGROUND: The performance of a statewide HIV rapid test algorithm (RTA) in a low-prevalence setting (0.71%) was examined for 3 years. METHODS: An initial rapid screening by HIV-1/2 Ag/Ab Combo test (RT#1) with Ab verification using a second, different rapid test (RT#2) was conducted. Clinic referral was immediate for antigen-only-positive screens. Antibody-positive screens were confirmed by RT#2. Specimens were collected following discordant RTA results (initially Ab-POS by RT#1, but negative on RT#2) and tested in accordance with the current Centers for Disease Control and Prevention/Association of Public Health Laboratories-based HIV diagnostic algorithm supplemented by a quantitative viral load whenever possible. RESULTS: Of 310,785 tests performed, 2400 preliminary positive screens were identified; 2191 (91.8%) confirmed by RT#2. Of 13 Determine Combo AG-POS results identified, only 1 confirmed positive. Of the remaining 196 discordant results, 182 (92.9%) were uninfected, including 13 with AG-POS/AB-POS results. Of 14 true positives (7.1%) identified after discordant RTA results, the average quantitative HIV-1 viral load was 277,385 copies/mL, but 5 (35.7%) of 14 had viral loads <1000 copies/mL. Among the 2191 "presumptive positive" by RTA, 3 false-positive (FP) RTAs were reported (both rapid tests having positive results, while the HIV-1/2 Ag/Ab assay and quantitative HIV-1 viral load showed negative results). CONCLUSIONS: The RTA was effective in predicting true-positive HIV test results and facilitating linkage to care. Discordant results were infrequent. Fingerstick DC Ag detection identified a single early infection. Many discordant cases that were subsequently positive were associated with viral loads <1000 copies/mL.

Determination of antibodies to human immunodeficiency virus type 1&2&O and P24 - antigen in pregnant women in port harcourt Nigeria.

The need for a cure against HIV infection and a need to improve HIV screening amongst low risk population such as pregnant women have been an issue since the emergence of HIV. Therefore, a hospital-based cross-sectional study was adopted to determine the prevalence of antibodies to HIV-1/2/O and P24 antigen among pregnant women in Port Harcourt, Nigeria. Estimating the HIV seropositivity in pregnant women will offer vital information for monitoring the trend of HIV infection in the general population and assist in prevention from mother-to-child transmission. The occurrence of antibodies to HIV type 1/2/O and P24 antigen among the pregnant women was investigated using fourth-generation ELISA. The influence of the women's age, marital status, occupation, educational status and gestation period on the prevalence of these antibodies against HIV type 1/2/O and P24 antigen was also considered. Of the 86 pregnant women, 14 were found to be HIV-positive with seropositivity rate of 32.6%. Majority of HIV seropositive women (41.2%) were in the age group of 31-42 years. Higher seropositivity was observed among singles (50.0%), those with secondary education (44.7%), unemployed (47.8%) and in those in their third trimester (40.0%). Additionally, this study observed high seropositivity of antibodies to HIV type 1, 2, O and P24 antigen among pregnant women in Port Harcourt, Nigeria and calls for urgent and concerted efforts aimed at promoting behavioral and socio-cultural practices that could change the current high rate of HIV seropositivity amongst pregnant women in Nigeria. A combination of preventive strategies such as the use of condoms, breaking the chain of transmission within sexual networks by prompt treatment and reducing the amount of unsafe sexual behavior, promoting sexual abstinence and behavioral change from high-risk behavior are advocated.

Evolution of an Electronic Health Record Based-Human Immunodeficiency Virus (HIV) Screening Program in an Urban Emergency Department for Diagnosing Acute and Chronic HIV Infection.

BACKGROUND: Since 2006, Centers for Disease Control and Prevention guidelines recommend routine opt-out human immunodeficiency virus (HIV) testing among sexually active 13- to 64-year-olds. Earlier diagnosis and treatment of HIV infection reduces morbidity and mortality and can limit transmission to others. OBJECTIVE: Our aim was to increase HIV testing, diagnosis, and linkage to care in the emergency department (ED). METHODS: Beginning May 4, 2015, we utilized our electronic health record (EHR) to enhance HIV testing in patients seen in the Rush University Medical Center emergency department in Chicago, IL, who were 13-64 years of age, did not have HIV listed on their problem list, and did not have an HIV antigen/antibody (Ag/Ab) test in the EHR within the past rolling 12-month period. Strategies included use of a "Best Practice Advisory" and later auto-order screening linked to a complete blood count order. RESULTS: Our baseline HIV test rate was 2.5% of the target population by age (average of 93 tests per month). From May 4, 2015 to January 31, 2019, 137,749 patients of 240,091 ED visits met our test criteria and 23,588 (17.1% of the target population) HIV Ag/Ab tests were performed, resulting in 164 positive tests. We identified 18 acute seroconverters, 51 new chronically infected persons, and 95 known infected, many of who had not disclosed their status. Our positive test rate was 0.70%, which dropped to 0.29% if only newly diagnosed individuals were counted. CONCLUSIONS: EHR enhancements in a large urban ED identifies both newly diagnosed acute and chronically HIV-infected persons. Identification of previously diagnosed patients offers an opportunity to relink them to care.

Analytical performance evaluation and enhancement of the ADVIA Centaur® HIV Ag/Ab Combo assay.

BACKGROUND: Fourth-generation immunoassays (such as the ADVIA Centaur® HIV Ag/Ab Combo (CHIV) assay) have improved the early diagnosis of human immunodeficiency virus (HIV), and their sensitivity and specificity usually exceed 99%. In regions with a low prevalence of HIV infection, however, the regular occurrence of false positives interferes with a medical laboratory's workflow. The additional reagent and staff costs associated with false positives can nevertheless be avoided or reduced by gaining a better knowledge of the CHIV assay's performance. OBJECTIVES/STUDY DESIGN: To improve our HIV diagnosis strategy, we retrospectively analyzed all the Centaur® CHIV assays and confirmatory tests performed at Amiens University Medical Center between 2012 and 2018. We used open-source machine learning software to process this large database, develop a predictive model, and identify a new cut-off for Centaur® CHIV index interpretation. RESULTS: A total of 56,682 HIV serological assay results were analyzed. The results of the CHIV assay were initially reactive or indeterminate for 449 samples. After p24 antigen and/or immunoblotting, there were 171 (38%) false positives and 278 (62%) confirmed true positives. The application of a cut-off of 2.12 led to reclassification of 130 of the 171 false positives as true negatives. Combining our predictive model with medical record analysis reduced the number of false positive CHIV assay results from 171 to 12. CONCLUSIONS: The efficiency of the Centaur® CHIV assay can be increased by adjusting its cut-off for positivity. This adjustment may reduce the number of unnecessary confirmatory tests and accelerate the delivery of HIV test results.

Acceptability, feasibility, and individual preferences of blood-based HIV self-testing in a population-based sample of adolescents in Kisangani, Democratic Republic of the Congo.

BACKGROUND: Adolescents living in sub-Saharan Africa constitute a vulnerable population at significant risk of HIV infection. This study aims to evaluate the acceptability, feasibility, and accuracy of home-based, supervised HIV self-testing (HIVST) as well as their predictors among adolescents living in Kisangani, Democratic Republic of the Congo (DRC). METHODS: A cross-sectional, door-to-door survey using a blood-based HIV self-test and a peer-based supervised HIVST approach was conducted from July to August 2018 in Kisangani, DRC. The acceptability and feasibility of HIVST were assessed among adolescents' consenting to use and interpret HIV self-test. The accuracy of HIVST was estimated by the sensibility and specificity of adolescent-interpreted HIV self-test. Factors associated with acceptability and feasibility of HIVST were analyzed with logistic regression. RESULTS: A total of 628 adolescents (including 369 [58.8%] females) aged between 15 and 19 years were enrolled. Acceptability of HIVST was high (95.1%); 96.1% of participants correctly used the self-test, and 65.2% asked for verbal instructions. The majority of adolescents (93.5%) correctly interpreted their self-test results. The Cohen's κ coefficient between the results read by adolescents and by supervisors was 0.62. The correct interpretation decreased significantly when adolescents had no formal education or attended primary school as compared to those currently attending university (37.0% versus 100%; adjusted OR: 0.01 [95% CI: 0.004-0.03]). In the hands of adolescents at home, the sensitivity of the Exacto Test HIV Self-test was estimated at 100%, while its specificity was 96.0%. The majority of participants (68.0%) affirmed that post-test counseling was essential, and that face-to-face counseling (78.9%) was greatly preferred. CONCLUSIONS: Home-based, supervised HIVST using a blood-based self-test and peer-based approach can be used with a high degree of acceptability and feasibility by adolescents living in Kisangani, DRC. Misinterpretation of test results is challenging to obtaining good feasibility of HIVST among adolescents with poor educational level. Face-to-face post-test counseling seems to be preferred among Kisangani's adolescents.

Ancestral sequences from an elite neutralizer proximal to the development of neutralization resistance as a potential source of HIV vaccine immunogens.

A major challenge in HIV vaccine development is the identification of immunogens able to elicit broadly neutralizing antibodies (bNAbs). While remarkable progress has been made in the isolation and characterization of bNAbs, the epitopes they recognize appear to be poorly immunogenic. Thus, none of the candidate vaccines developed to date has induced satisfactory levels of neutralizing antibodies to the HIV envelope protein (Env). One approach to the problem of poor immunogenicity is to build vaccines based on envelope (env) genes retrieved from rare individuals termed elite neutralizers (ENs) who at one time possessed specific sequences that stimulated the formation of bNAbs. Env proteins selected from these individuals could possess uncommon, yet to be defined, structural features that enhance the immunogenicity of epitopes recognized by bNAbs. Here we describe the recovery of envs from an EN that developed unusually broad and potent bNAbs. As longitudinal specimens were not available, we combined plasma and provirus sequences acquired from a single time-point to infer a phylogenetic tree. Combining ancestral reconstruction data with virus neutralization data allowed us to sift through the myriad of virus quasi-species that evolved in this individual to identify envelope sequences from the nodes that appeared to define the transition from neutralization sensitive envs to the neutralization resistant envs that occur in EN plasma. Synthetic genes from these nodes were functional in infectivity assays and sensitive to neutralization by bNAbs, and may provide a novel source of immunogens for HIV vaccine development.

Seroprevalence of HCV, HBV and HIV in two inner-city London emergency departments.

SUMMARY: In this paper we build on work investigating the feasibility of human immunodeficiency virus (HIV) testing in emergency departments (EDs), estimating the prevalence of hepatitis B, C and HIV infections among persons attending two inner-London EDs, identifying factors associated with testing positive in an ED. We also undertook molecular characterisation to look at the diversity of the viruses circulating in these individuals, and the presence of clinically significant mutations which impact on treatment and control.Blood-borne virus (BBV) testing in non-traditional settings is feasible, with emergency departments (ED) potentially effective at reaching vulnerable and underserved populations. We investigated the feasibility of BBV testing within two inner-London EDs. Residual samples from biochemistry for adults (⩾18 years) attending The Royal Free London Hospital (RFLH) or the University College London Hospital (UCLH) ED between January and June 2015 were tested for human immunodeficiency virus (HIV)Ag/Ab, anti-hepatitis C (HCV) and HBsAg. PCR and sequence analysis were conducted on reactive samples. Sero-prevalence among persons attending RFH and UCLH with residual samples (1287 and 1546), respectively, were 1.1% and 1.0% for HBsAg, 1.6% and 2.3% for anti-HCV, 0.9% and 1.6% for HCV RNA, and 1.3% and 2.2% for HIV. For RFH, HBsAg positivity was more likely among persons of black vs. white ethnicity (odds ratio 9.08; 95% confidence interval 2.72-30), with anti-HCV positivity less likely among females (0.15, 95% CI 0.04-0.50). For UCLH, HBsAg positivity was more likely among non-white ethnicity (13.34, 95% CI 2.20-80.86 (Asian); 8.03, 95% CI 1.12-57.61 (black); and 8.11, 95% CI 1.13-58.18 (other/mixed)). Anti-HCV positivity was more likely among 36-55 year olds vs. ⩾56 years (7.69, 95% CI 2.24-26.41), and less likely among females (0.24, 95% CI 0.09-0.65). Persons positive for HIV-markers were more likely to be of black vs. white ethnicity (4.51, 95% CI 1.63-12.45), and less likely to have one ED attendance (0.39, 95% CI 0.17-0.88), or female (0.12, 95% CI 0.04-0.42). These results indicate that BBV-testing in EDs is feasible, providing a basis for further studies to explore provider and patient acceptability, referral into care and cost-effectiveness.

Sample-to-cutoff ratios using Architect HIV Ag/Ab Combo: The influence with the results of supplemental tests and optimal cutoff value to predict HIV infection.

BACKGROUND: The Architect HIV Ag/Ab Combo has excellent performance for HIV screening; however, the false-positive rate (FPR) was high in low HIV prevalence setting. OBJECTIVES: The purpose of this study was to analyze the influence of sample-to-cutoff (s/co) ratios by Architect HIV Ag/Ab Combo with the results of confirmatory test and explore the potential utility of s/co to predict HIV infection. METHODS: A retrospective review on Architect HIV Ag/Ab Combo reactive results was performed at a teaching hospital in Xi'an. The s/co values in different groups, that is, true positives (TP) and false positives (FP), different Western blotting (WB) bands among WB-positive cases, were compared. The receiver operating characteristic curve (ROC) analysis was used to determine the optimal cutoff value for predicting HIV infection. RESULTS: During the study period, 219 out of 84 702 patients were reactive by ARCHITECT with a 0.0992% of HIV prevalence and a 56.25% of FPR. The mean s/co ratios in TP were significantly higher than that in FP (458.15 vs 3.11, P < 0.0001). Among the WB-positive cases, the s/co ratios increased significantly with the increase in the number of bands, P = 0.0065. The optimal cutoff (24.44) by ROC analysis can provide the highest sum of sensitivity (100%) and specificity (100%) with no FP results. CONCLUSIONS: For Architect HIV Ag/Ab Combo, the FPR is reduced when s/co ratios increase, and the s/co ≥24.44 may be reliable to predict HIV infection.

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.

Validation of the Limiting Antigen Avidity Assay to Estimate Level and Trends in HIV Incidence in an A/D Epidemic in Rakai, Uganda.

The limiting-antigen avidity (LAg-Avidity) assay with viral load (VL) >1,000 copies/mL is being used to estimate population-level HIV incidence in Africa. However, this has not been validated in East Africa where HIV-1 subtypes A and D circulate. Sera from persons seen in two surveys (2008-2009 and 2012-2013) limited to those who attended the previous round of the Rakai Community Cohort in Uganda were analyzed. The performance of the current LAg-Avidity protocol, with a mean duration of recent infection (MDRI) of 130 days and false recent rate (FRR) of 0%, was compared with subtype-specific MDRI and FRR, adjusted to subtype distributions. The observed incidence was 1.05/100 person years (py) [95% confidence interval (CI) 0.90-1.23] in 2008-2009 and 0.66/100 py (95% CI 0.52-0.83) in 2012-2013. In contrast, the per-protocol LAg-Avidity incidence estimates were 1.63/100 py (95% CI 0.97-2.30) in 2008-2009 and 2.55/100 py (95% CI 1.51-3.59) in 2012-2013 (a significant increase, p < .05.) However, using a subtype-specific MDRI and FRR, the subtype adjusted incidence was 0.88% (95% CI 0.44-1.33) in 2008-2009 and 0.67% (95% CI 0.00-1.68) in 2012-2013, approximating to the observed incidence trends. In this subtype A/D epidemic, the per protocol LAg-Avidity + VL assay overestimated HIV incidence and failed to detect declines in incidence. Adjustment for FRR, MDRI, and subtype distribution provided incidence estimates similar to empirically observed incidence level and trends. Thus, use of the LAg-Avidity assay in an A/D epidemic requires adjustment for subtype.

Stability of Human Immunodeficiency Virus Serological Markers in Samples Collected as HemaSpot and Whatman 903 Dried Blood Spots.

Dried blood spots (DBS) are frequently used in clinical testing for biosurveillance, infectious disease and confirmatory testing, and clinical trials, particularly for populations in remote areas. The HemaSpot-HF blood collection device (HS) provides an alternative format to the Whatman 903 cards (903) to simplify sample collection and processing. In this study, the performance of the HS was compared to that of the 903 using previously characterized clinical specimens and HIV seroconversion panels known to exhibit markers of early human immunodeficiency virus (HIV) infection. HS and 903 samples were prepared and tested by Bio-Rad GS HIV Combo Ag/Ab enzyme immunoassay (EIA), GS HIV-1/-2 Plus O EIA, GS HIV-1 Western blot, and HIV-1 Geenius assays. Both HS and 903 performed well for up to 6 months at room temperature, but a marked loss of Western blot and low titer antibody signals from early infection samples was observed in samples stored for 180 days at elevated (37 to 45°C) temperatures and high humidity (95%). HemaSpot samples placed in sealed bags with additional desiccant were protected from degradation and showed improved signal recovery relative to that of the 903. HS was easier to use than the 903 and showed higher sensitivity and reproducibility for early infection samples and improved stability.

Performance of the Alere Determine™ HIV-1/2 Ag/Ab Combo Rapid Test with algorithm-defined acute HIV-1 infection specimens.

BACKGROUND: The capacity of HIV Antigen/Antibody (Ag/Ab) immunoassays (IA) to detect HIV-1 p24 antigen has resulted in improved detection of HIV-1 infections in comparison to Ab-only screening assays. Since its introduction in the US, studies have shown that the Determine HIV-1/2 Ag/Ab Combo assay (Determine Ag/Ab) detects HIV infection earlier than laboratory-based IgM/IgG-sensitive IAs, but its sensitivity for HIV-1 p24 Ag detection is reduced compared to laboratory-based Ag/Ab assays. However, further evaluation is needed to assess its capacity to detect acute HIV-1 infection. OBJECTIVE: To assess the performance of Determine Ag/Ab in serum from acute HIV-1 infections. STUDY DESIGN: Select serum specimens that screened reactive on a laboratory-based Ag/Ab IA or IgM/IgG Ab-only IA, with a negative or indeterminate supplemental antibody test and detectable HIV-1 RNA were retrospectively tested with Determine Ag/Ab. Results were compared with those of the primary screening immunoassay to evaluate concordance within this set of algorithm-defined acute infections. RESULTS: Of 159 algorithm-defined acute HIV-1 specimens, Determine Ag/Ab was reactive for 105 resulting in 66.0% concordance. Of 125 that were initially detected by a laboratory-based Ag/Ab IA, 81 (64.8%) were reactive by Determine Ag/Ab. A total of 34 acute specimens were initially detected by a laboratory-based IgM/IgG Ab-only IA and 24 (70.6%) of those were reactive by Determine Ag/Ab. CONCLUSIONS: Due to their enhanced sensitivity, laboratory-based Ag/Ab IAs continue to be preferred over the Determine Ag/Ab as the screening method used by laboratories conducting HIV diagnostic testing on serum and plasma specimens.

Comparison of Detection Limits of Fourth- and Fifth-Generation Combination HIV Antigen-Antibody, p24 Antigen, and Viral Load Assays on Diverse HIV Isolates.

Detection of acute HIV infection is critical for HIV public health and diagnostics. Clinical fourth-generation antigen (Ag)/antibody (Ab) combination (combo) and p24 Ag immunoassays have enhanced detection of acute infection compared to Ab-alone assays but require ongoing evaluation with currently circulating diverse subtypes. Genetically and geographically diverse HIV clinical isolates were used to assess clinical HIV diagnostic, blood screening, and next-generation assays. Three-hundred-member panels of 20 serially diluted well-characterized antibody-negative HIV isolates for which the researchers were blind to the results (blind panels) were distributed to manufacturers and end-user labs to assess the relative analytic sensitivity of currently approved and preapproved clinical HIV fourth-generation Ag/Ab combo or p24 Ag-alone immunoassays for the detection of diverse subtypes. The limits of detection (LODs) of virus were estimated for different subtypes relative to confirmed viral loads. Analysis of immunoassay sensitivity was benchmarked against confirmed viral load measurements on the blind panel. On the basis of the proportion of positive results on 300 observations, all Ag/Ab combo and standard sensitivity p24 Ag assays performed similarly and within half-log LODs, illustrating the similar breadth of reactivity and diagnostic utility. Ultrasensitive p24 Ag assays achieved dramatically increased sensitivities, while the rapid combo assays performed poorly. The similar performance of the different commercially available fourth-generation assays on diverse subtypes supports their use in broad geographic settings with locally circulating HIV clades and recombinant strains. Next-generation preclinical ultrasensitive p24 Ag assays achieved dramatically improved sensitivity, while rapid fourth-generation assays performed poorly for p24 Ag detection.

Heterophilic interference in specimens yielding false-reactive results on the Abbott 4th generation ARCHITECT HIV Ag/Ab Combo assay.

BACKGROUND: False-reactivity in HIV-negative specimens has been detected in HIV fourth-generation antigen/antibody or 'combo' assays which are able to detect both anti-HIV-1/HIV-2 antibodies and HIV-1 antigen. OBJECTIVES: We sought to characterize these specimens and determine the effect of heterophilic interference. STUDY DESIGN: Specimens previously testing as false-reactive on the Abbott ARCHITECT HIV Ag/Ab combo assay and re-tested on a different (Siemens ADVIA Centaur HIV Ag/Ab) assay. A subset of these specimens were also pre-treated with heterophilic blocking agents and re-tested on the Abbott assay. RESULTS: Here we report that 95% (252/264) of clinical specimens that were repeatedly reactive on the Abbott ARCHITECT HIV Ag/Ab combo assay (S/Co range, 0.94-678) were negative when re-tested on a different fourth generation HIV combo assay (Siemens ADVIA Centaur HIV Ag/Ab). All 264 samples were subsequently confirmed to be HIV negative. On a small subset (57) of specimens with available volume, pre-treatment with two different reagents (HBT; Heterophilic Blocking Tube, NABT; Non-Specific Blocking Tube) designed to block heterophilic antibody interference either eliminated (HBT) or reduced (NABT) the false reactivity when re-tested on the ARCHITECT HIV Ag/Ab combo assay. CONCLUSIONS: Our results suggest that the Abbott ARCHITECT HIV Ag/Ab combo assay can be prone to heterophilic antibody interference.

Evaluation of the Architect HIV Ag/Ab Combo Assay in a low-prevalence setting: The role of samples with a low S/CO ratio.

BACKGROUND: The Architect HIV Ag/Ab Combo Assay, a fourth-generation ELISA, has proven to be highly reliable for the diagnosis of HIV infection. However, its high sensitivity may lead to false-positive results. OBJECTIVES: To evaluate the diagnostic performance of Architect in a low-prevalence population and to assess the role of the sample-to-cutoff ratio (S/CO) in reducing the frequency of false-positive results. STUDY DESIGN: We conducted a retrospective study of samples analyzed by Architect between January 2015 and June 2017. Positive samples were confirmed by immunoblot (RIBA) or nucleic acid amplification tests (NAATs). Different S/CO thresholds (1, 2.5, 10, 25, and 100) were analyzed to determine sensitivity, specificity, and negative and positive predictive values (NPV, PPV). ROC analysis was used to determine the optimal S/CO. RESULTS: A total of 69,471 samples were analyzed. 709 (1.02%) were positive by Architect. Of these, 63 (8.89%) were false-positive results. Most of them (93.65%) were in samples with S/CO < 100. However, most confirmations by NAATs (12 out of 19 cases) were also recorded for these samples. The optimal S/CO was 2.5, which provided the highest area under the ROC curve (0.9998) and no false-negative results. With this S/CO, sensitivity and specificity were 100.0%, and PPV and NPV were 95.8% and 100.0%, respectively. In addition, the frequency of false-positive results decreased significantly to 4.15%. CONCLUSIONS: Although Architect generates a relatively high number of false-positive results, raising the S/CO limit too much to increase specificity can lead to false-negative results, especially in newly infected individuals.

An analysis of the predictive value of the HIV Ag/Ab screening assay within the performance characteristics of the DiaSorin LIAISON XL for the detection of blood-borne viruses.

BACKGROUND: Correct identification of blood borne viral infections, such as hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV) is crucial in detection and follow up of infection in patients. OBJECTIVES: We evaluated the diagnostic performance of the DiaSorin LIAISON XL (LIAISON XL) for screening of HBV, HCV and HIV infection. In addition, we investigated the variability of the signal-to-cuttoff ratio (S/CO) of the LIAISON XL HIV Ag/Ab assay and it's predictive value in subsequent confirmation of HIV-1 infection. STUDY DESIGN: We analyzed 16,497 blood samples on which HBV, HCV and HIV screening was performed. We defined A) archived samples previously tested with an arbitrary result in the Abbott ARCHITECT i2000SR system; B) prospectively collected samples which were simultaneously tested on the LIAISON XL and ARCHITECT i2000SR; C) prospectively collected serum samples for HIV testing which were tested solely on the LIAISON XL. RESULTS: The agreements of HBV-, HCV-, and HIV markers between the two compared systems are remarkably high. Among the samples which were prospectively tested for HIV Ab/Ag on the LIASON XL, 229 (1.6%) were reactive of which 141 (61.6%) could be confirmed. Increasing the signal-to-cutoff value to 4 could increase the positive predictive value (PPV) to 88.1% without decreasing sensitivity. CONCLUSIONS: The LIAISON XL system proved to be an excellent system for diagnosing HBV, HCV, and HIV. Our data for the first time showed that increasing the HIV S/CO ratio was safe and increased the PPV for confirmed HIV infection in the tested population.