Cost savings associated with testing of antibodies, antigens, and nucleic acids for diagnosis of acute HIV infection

Electrochemical Strategy for Low-Cost Viral Detection

Sexually transmitted infections, including the human immunodeficiency virus (HIV) and the human papillomavirus (HPV), disproportionally impact those in low-resource settings. Early diagnosis is essential for managing HIV. Similarly, HPV causes nearly all cases of cervical cancer, the majority (90%) of which occur in low-resource settings. Importantly, infection with HPV is six times more likely to progress to cervical cancer in women who are HIV-positive. An inexpensive, adaptable point-of-care test for viral infections would make screening for these viruses more accessible to a broader set of the population. Here, we report a novel, cost-effective electrochemical platform using gold leaf electrodes to detect clinically relevant viral loads. We have combined this platform with loop-mediated isothermal amplification and a CRISPR-based recognition assay to detect HPV. Lower limits of detection were demonstrated down to 10⁴ total copies of input nucleic acids, which is a clinically relevant viral load for HPV DNA. Further, proof-of-concept experiments with cervical swab samples, extracted using standard extraction protocols, demonstrated that the strategy is extendable to complex human samples. This adaptable technology could be applied to detect any viral infection rapidly and cost-effectively.

A methodology for deriving the sensitivity of pooled testing, based on viral load progression and pooling dilution

BACKGROUND

Pooled testing, in which biological specimens from multiple subjects are combined into a testing pool and tested via a single test, is a common testing method for both surveillance and screening activities. The sensitivity of pooled testing for various pool sizes is an essential input for surveillance and screening optimization, including testing pool design. However, clinical data on test sensitivity values for different pool sizes are limited, and do not provide a functional relationship between test sensitivity and pool size. We develop a novel methodology to accurately compute the sensitivity of pooled testing, while accounting for viral load progression and pooling dilution. We demonstrate our methodology on the nucleic acid amplification testing (NAT) technology for the human immunodeficiency virus (HIV).

METHODS

Our methodology integrates mathematical models of viral load progression and pooling dilution to derive test sensitivity values for various pool sizes. This methodology derives the conditional test sensitivity, conditioned on the number of infected specimens in a pool, and uses the law of total probability, along with higher dimensional integrals, to derive pooled test sensitivity values. We also develop a highly accurate and easy-to-compute approximation function for pooled test sensitivity of the HIV ULTRIO Plus NAT Assay. We calibrate model parameters using published efficacy data for the HIV ULTRIO Plus NAT Assay, and clinical data on viral RNA load progression in HIV-infected patients, and use this methodology to derive and validate the sensitivity of the HIV ULTRIO Plus Assay for various pool sizes.

RESULTS

We demonstrate the value of this methodology through optimal testing pool design for HIV prevalence estimation in Sub-Saharan Africa. This case study indicates that the optimal testing pool design is highly efficient, and outperforms a benchmark pool design.

CONCLUSIONS

The proposed methodology accounts for both viral load progression and pooling dilution, and is computationally tractable. We calibrate this model for the HIV ULTRIO Plus NAT Assay, show that it provides highly accurate sensitivity estimates for various pool sizes, and, thus, yields efficient testing pool design for HIV prevalence estimation. Our model is generic, and can be calibrated for other infections.

p24 revisited: a landscape review of antigen detection for early HIV diagnosis

: Despite major advances in HIV testing, early detection of infection at the point of care (PoC) remains a key challenge. Although rapid antibody PoC and laboratory-based nucleic acid amplification tests dominate the diagnostics market, the viral capsid protein p24 is recognized as an alternative early virological biomarker of infection. However, the detection of ultra-low levels of p24 at the PoC has proven challenging. Here we review the landscape of p24 diagnostics to identify knowledge gaps and barriers and help shape future research agendas. Five hundred and seventy-four research articles to May 2018 that propose or evaluate diagnostic assays for p24 were identified and reviewed. We give a brief history of diagnostic development, and the utility of p24 as a biomarker in different populations such as infants, the newly infected, those on preexposure prophylaxis and self-testers. We review the performance of commercial p24 assays and consider elements such as immune complex disruption, resource-poor settings, prevalence, and assay antibodies. Emerging and ultrasensitive assays are reviewed and show a number of promising approaches but further translation has been limited. We summarize studies on the health economic benefits of using antigen testing. Finally, we speculate on the future uses of high-performance p24 assays, particularly, if available in self-test format.

Sequential prevalence estimation with pooling and continuous test outcomes

Prevalence estimation is crucial for controlling the spread of infections and diseases and for planning of health care services. Prevalence estimation is typically conducted via pooled, or group, testing due to limited testing budgets. We study a sequential estimation procedure that uses continuous pool readings and considers the dilution effect of pooling so as to efficiently estimate an unknown prevalence rate. Embedded into the sequential estimation procedure is an optimization model that determines the optimal pooling design (number of pools and pool sizes) under a limited testing budget, considering the trade-off between testing cost and estimation accuracy. Our numerical study indicates that the proposed sequential estimation procedure outperforms single-stage procedures, or procedures that use binary test outcomes. Further, the sequential procedure provides robust prevalence estimates in cases where the initial estimate of the unknown prevalence rate is poor, or the assumed distribution of the biomarker load in infected subjects is inaccurate. Thus, when limited and unreliable information is available about the current status of, or biomarker dynamics related to, an infection, the sequential procedure becomes an attractive estimation strategy, due to its ability to mitigate the initial bias.

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.

Clinical and public health implications of acute and early HIV detection and treatment: a scoping review

INTRODUCTION

The unchanged global HIV incidence may be related to ignoring acute HIV infection (AHI). This scoping review examines diagnostic, clinical, and public health implications of identifying and treating persons with AHI.

METHODS

We searched PubMed, in addition to hand-review of key journals identifying research pertaining to AHI detection and treatment. We focused on the relative contribution of AHI to transmission and the diagnostic, clinical, and public health implications. We prioritized research from low- and middle-income countries (LMICs) published in the last fifteen years.

RESULTS AND DISCUSSION

Extensive AHI research and limited routine AHI detection and treatment have begun in LMIC. Diagnostic challenges include ease-of-use, suitability for application and distribution in LMIC, and throughput for high-volume testing. Risk score algorithms have been used in LMIC to screen for AHI among individuals with behavioural and clinical characteristics more often associated with AHI. However, algorithms have not been implemented outside research settings. From a clinical perspective, there are substantial immunological and virological benefits to identifying and treating persons with AHI - evading the irreversible damage to host immune systems and seeding of viral reservoirs that occurs during untreated acute infection. The therapeutic benefits require rapid initiation of antiretrovirals, a logistical challenge in the absence of point-of-care testing. From a public health perspective, AHI diagnosis and treatment is critical to: decrease transmission via viral load reduction and behavioural interventions; improve pre-exposure prophylaxis outcomes by avoiding treatment initiation for HIV-seronegative persons with AHI; and, enhance partner services via notification for persons recently exposed or likely transmitting.

CONCLUSIONS

There are undeniable clinical and public health benefits to AHI detection and treatment, but also substantial diagnostic and logistical barriers to implementation and scale-up. Effective early ART initiation may be critical for HIV eradication efforts, but widespread use in LMIC requires simple and accurate diagnostic tools. Implementation research is critical to facilitate sustainable integration of AHI detection and treatment into existing health systems and will be essential for prospective evaluation of testing algorithms, point-of-care diagnostics, and efficacious and effective first-line regimens.

Comparison of 4th-Generation HIV Antigen/Antibody Combination Assay With 3rd-Generation HIV Antibody Assays for the Occurrence of False-Positive and False-Negative Results

OBJECTIVE

To assess the false-positive and false-negative rates of a 4th-generation human immunodeficiency virus (HIV) assay, the Abbott ARCHITECT, vs 2 HIV 3rd-generation assays, the Siemens Centaur and the Ortho-Clinical Diagnostics Vitros.

METHODS

We examined 123 patient specimens. In the first phase of the study, we compared 99 specimens that had a positive screening result via the 3rd-generation Vitros assay (10 positive, 82 negative, and 7 indeterminate via confirmatory immunofluorescent assay [IFA]/Western blot [WB] testing). In the second phase, we assessed 24 HIV-1 RNA-positive (positive result via the nuclear acid amplification test [NAAT] and negative/indeterminate results via the WB test) specimens harboring acute HIV infection.

RESULTS

The 4th-generation ARCHITECT assay yielded fewer false-positive results (n = 2) than the 3rd-generation Centaur (n = 9; P = .02) and Vitros (n = 82; P <.001) assays. One confirmed positive case had a false-negative result via the Centaur assay. When specimens from the 24 patients with acute HIV-1 infection were tested, the ARCHITECT assay yielded fewer false-negative results (n = 5) than the Centaur (n = 10) (P = .13) and the other 3rd-generation tests (n = 16) (P = .002).

CONCLUSIONS

This study indicates that the 4th-generation ARCHITECT HIV assay yields fewer false-positive and false-negative results than the 3rd-generation HIV assays we tested.

Incorporating Acute HIV Screening into Routine HIV Testing at Sexually Transmitted Infection Clinics, and HIV Testing and Counseling Centers in Lilongwe, Malawi

Background and Objectives:

Integrating acute HIV-infection (AHI) testing into clinical settings is critical to prevent transmission, and realize potential treatment-as-prevention benefits. We evaluated acceptability of AHI testing and compared AHI prevalence at sexually transmitted infection (STI) clinics and HIV testing and counseling (HTC) clinics in Lilongwe, Malawi.

Methods:

We conducted HIV RNA testing for HIV-seronegative patients visiting STI and HTC clinics. AHI was defined as positive RNA and negative/discordant rapid antibody tests. We evaluated demographic, behavioral, and transmission-risk differences between STI and HTC patients and assessed performance of a risk-score for targeted screening.

Results:

Nearly two-thirds (62.8%, 9280/14,755) of eligible patients consented to AHI testing. We identified 59 persons with AHI (prevalence = 0.64%)–a 0.9% case-identification increase. Prevalence was higher at STI [1.03% (44/4255)] than at HTC clinics [0.3% (15/5025), P < 0.01], accounting for 2.3% of new diagnoses vs 0.3% at HTC clinic. Median viral load (VL) was 758,050 copies per milliliter; 25% (15/59) had VL ≥10,000,000 copies per milliliter. Median VL was higher at STI (1,000,000 copies/mL) compared with HTC (153,125 copies/mL, P = 0.2). Among persons with AHI, those tested at STI clinics were more likely to report genital sores compared with those tested at HTC clinics (54.6% vs 6.7%, P < 0.01). The risk score algorithm performed well in identifying persons with AHI at HTC clinics (sensitivity = 73%, specificity = 89%).

Conclusions:

The majority of patients consented to AHI testing. AHI prevalence was substantially higher in STI clinics than HTC clinics. Remarkably high VLs and concomitant genital scores demonstrate the potential for transmission. Universal AHI screening at STI clinics, and targeted screening at HTC centers, should be considered.

Costs per Diagnosis of Acute HIV Infection in Community-based Screening Strategies: A Comparative Analysis of Four Screening Algorithms

BACKGROUND

In nonhealthcare settings, widespread screening for acute human immunodeficiency virus (HIV) infection (AHI) is limited by cost and decision algorithms to better prioritize use of resources. Comparative cost analyses for available strategies are lacking.

METHODS

To determine cost-effectiveness of community-based testing strategies, we evaluated annual costs of 3 algorithms that detect AHI based on HIV nucleic acid amplification testing (EarlyTest algorithm) or on HIV p24 antigen (Ag) detection via Architect (Architect algorithm) or Determine (Determine algorithm) as well as 1 algorithm that relies on HIV antibody testing alone (Antibody algorithm). The cost model used data on men who have sex with men (MSM) undergoing community-based AHI screening in San Diego, California. Incremental cost-effectiveness ratios (ICERs) per diagnosis of AHI were calculated for programs with HIV prevalence rates between 0.1% and 2.9%.

RESULTS

Among MSM in San Diego, EarlyTest was cost-savings (ie, ICERs per AHI diagnosis less than $13.000) when compared with the 3 other algorithms. Cost analyses relative to regional HIV prevalence showed that EarlyTest was cost-effective (ie, ICERs less than $69.547) for similar populations of MSM with an HIV prevalence rate >0.4%; Architect was the second best alternative for HIV prevalence rates >0.6%.

CONCLUSIONS

Identification of AHI by the dual EarlyTest screening algorithm is likely to be cost-effective not only among at-risk MSM in San Diego but also among similar populations of MSM with HIV prevalence rates >0.4%.

Repeat HIV-testing is associated with an increase in behavioral risk among men who have sex with men: a cohort study

BACKGROUND

The Center for Disease Control and Prevention recommends that high-risk groups, like sexually active men who have sex with men (MSM), receive HIV testing and counseling at least annually. The objective of this study was to investigate the relationship between voluntary repeat HIV testing and sexual risk behavior in MSM receiving rapid serologic and nucleic acid amplification testing.

METHODS

We performed a cohort study to analyze reported risk behavior among MSM receiving the "Early Test", a community-based, confidential acute and early HIV infection screening program in San Diego, California, between April 2008 and July 2014. The study included 8,935 MSM receiving 17,333 "Early Tests". A previously published risk behavior score for HIV acquisition in MSM (i.e. Menza score) was chosen as an outcome to assess associations between risk behaviors and number of repeated tests.

RESULTS

At baseline, repeat-testers (n = 3,202) reported more male partners and more condomless receptive anal intercourse (CRAI) when compared to single-testers (n = 5,405, all P <0.001). In 2,457 repeat testers there was a strong association observed between repeated HIV tests obtained and increased risk behavior, with number of male partners, CRAI with high risk persons, non-injection stimulant drug use, and sexually transmitted infections all increasing between the first and last test. There was also a linear increase of risk (i.e. high Menza scores) with number of tests up to the 17th test. In the multivariable mixed effects model, more HIV tests (OR = 1.18 for each doubling of the number of tests, P <0.001) and younger age (OR = 0.95 per 5-year increase, P = 0.006) had significant associations with high Menza scores.

CONCLUSIONS

This study found that the highest risk individuals for acquiring HIV (e.g. candidates for antiretroviral pre-exposure prophylaxis) can be identified by their testing patterns. Future studies should delineate causation versus association to improve prevention messages delivered to repeat testers during HIV testing and counseling sessions.

Evaluation of performance of human immunodeficiency virus antigen/antibody combination assays in Taiwan

BACKGROUND

The fourth-generation human immunodeficiency virus (HIV) combination assay, which can simultaneously detect the presence of anti-HIV antibody and HIV antigen, has been shown to shorten the window period in HIV diagnosis compared with the third-generation HIV antibody immunoassay. This study was aimed to determine the performance of HIV combination assays in Taiwan, where the HIV-1 seroprevalence is 0.007% and HIV-2 infection has never been reported.

METHODS

Performance of three fourth-generation HIV Ag/Ab combination assays (Dia.Pro, Wantai, and Bio-Rad) and one third-generation HIV Ab immunoassay (AxSYM HIV 1/2 gO) was assessed.

RESULTS

A total of 152 specimens, including 86 confirmed HIV-seropositive and 66 HIV-seronegative samples, were used in the study. The sensitivity of four assays varied from 98.8% to 100%, and specificity varied from 98.5% to 100%. Performance of the 75 equivocal samples, the HIV status of which was confirmed later, in terms of negative prediction varied from 81.8% to 87.5%. The Bio-Rad and Dia.Pro assays exhibited higher sensitivity for the detection of p24 antigen among the three fourth-generation HIV combination assays.

CONCLUSION

The three fourth-generation HIV Ag/Ab combination assays exhibited better sensitivity, specificity, and negative prediction than the third-generation HIV Ab immunoassay.

Impact of nucleic acid testing relative to antigen/antibody combination immunoassay on the detection of acute HIV infection

OBJECTIVE

To assess the addition of HIV nucleic acid testing (NAT) to fourth-generation (4thG) HIV antigen/antibody combination immunoassay in improving detection of acute HIV infection (AHI).

METHODS

Participants attending a major voluntary counseling and testing site in Thailand were screened for AHI using 4thG HIV antigen/antibody immunoassay and sequential less sensitive HIV antibody immunoassay. Samples nonreactive by 4thG antigen/antibody immunoassay were further screened using pooled NAT to identify additional AHI. HIV infection status was verified following enrollment into an AHI study with follow-up visits and additional diagnostic tests.

RESULTS

Among 74 334 clients screened for HIV infection, HIV prevalence was 10.9% and the overall incidence of AHI (N = 112) was 2.2 per 100 person-years. The inclusion of pooled NAT in the testing algorithm increased the number of acutely infected patients detected, from 81 to 112 (38%), relative to 4thG HIV antigen/antibody immunoassay. Follow-up testing within 5 days of screening marginally improved the 4thG immunoassay detection rate (26%). The median CD4 T-cell count at the enrollment visit was 353 cells/μl and HIV plasma viral load was 598 289 copies/ml.

CONCLUSION

The incorporation of pooled NAT into the HIV testing algorithm in high-risk populations may be beneficial in the long term. The addition of pooled NAT testing resulted in an increase in screening costs of 22% to identify AHI: from $8.33 per screened patient to $10.16. Risk factors of the testing population should be considered prior to NAT implementation given the additional testing complexity and costs.

Prevalence of undiagnosed acute and chronic HIV in a lower-prevalence urban emergency department

OBJECTIVES

We estimated the seroprevalence of both acute and chronic HIV infection by using a random sample of emergency department (ED) patients from a region of the United States with low-to-moderate HIV prevalence.

METHODS

This cross-sectional seroprevalence study consecutively enrolled patients aged 18 to 64 years within randomly selected sampling blocks in a Midwestern urban ED in a region of lower HIV prevalence in 2008 to 2009. Participants were compensated for providing a blood sample and health information. After de-identification, we assayed samples for HIV antibody and nucleic acid.

RESULTS

There were 926 participants who consented and enrolled. Overall, prevalence of undiagnosed HIV was 0.76% (95% confidence interval [CI] = 0.30%, 1.56%). Three participants (0.32%; 95% CI = 0.09%, 0.86%) were nucleic acid-positive but antibody-negative and 4 (0.43%; 95% CI = 0.15%, 1.02%) were antibody-positive.

CONCLUSIONS

Even when the absolute prevalence is low, a considerable proportion of undetected HIV cases in an ED population are acute. Identification of acute HIV in ED settings should receive increased priority.

Pooled nucleic acid testing increases the diagnostic yield of acute HIV infections in a high-risk population compared to 3rd and 4th generation HIV enzyme immunoassays

OBJECTIVES

We compared a 3rd generation (gen) and two 4th gen HIV enzyme immunoassays (EIA) to pooled nucleic acid testing (PNAT) for the identification of pre- and early seroconversion acute HIV infection (AHI).

STUDY DESIGN

9550 specimens from males >18 year from clinics attended by men who have sex with men were tested by Siemens ADVIA Centaur(®) HIV 1/O/2 (3rd gen) and HIV Combo (4th gen), as well as by Abbott ARCHITECT(®) HIV Ag/Ab Combo (4th gen). Third gen non-reactive specimens were also tested by Roche COBAS(®) Ampliprep/COBAS® TaqMan HIV-1 Test v.2 in pools of 24 samples. Sensitivity and specificity of the three EIAs for AHI detection were compared.

RESULTS

7348 persons contributed 9435 specimens and had no evidence of HIV infection, 79 (94 specimens) had established HIV infection, 6 (9 specimens) had pre-seroconversion AHI and 9 (12 specimens) had early seroconversion AHI. Pre-seroconversion AHI cases were not detected by 3rd gen EIA, whereas 2/6 (33.3%) were detected by Siemens 4th gen, 4/6 (66.7%) by Abbott 4th gen and 6/6 (100%) by PNAT. All three EIAs and PNAT detected all individuals with early seroconversion AHI. Overall sensitivity/specificity for the EIAs relative to WB or NAT resolved infection status was 93.6%/99.9% for Siemens 3rd gen, 95.7%/99.7% for Siemens 4th gen and 97.9%/99.2% for Abbott 4th gen.

CONCLUSIONS

While both 4th gen EIAs demonstrated improved sensitivity for AHI compared to 3rd gen EIA, PNAT identified more AHI cases than either 4th gen assay. PNAT is likely to remain a useful strategy to identify AHI in high-risk populations.

Identification of acute HIV infection using fourth-generation testing in an opt-out emergency department screening program

STUDY OBJECTIVE

Acute HIV infection is a clinical diagnosis aided by technology. Detecting the highly infectious acute stage of HIV infection is critical to reducing transmission and improving long-term outcomes. The Maricopa Integrated Health System implemented nontargeted, opt-out HIV screening with a fourth-generation antigen/antibody combination HIV assay test in our adult emergency department (ED) at Maricopa Medical Center to assess the prevalence of both acute and chronic unrecognized HIV.

METHODS

Eligible patients aged 18 to 64 years were tested for HIV if they did not opt out and had blood drawn as part of their ED care. Patients were not eligible if they had a known HIV or AIDS diagnosis, exhibited altered mental status, were a current resident of a long-term psychiatric or correctional facility, or prompted a trauma activation. Reactive test results were delivered by a physician with the assistance of a linkage-to-care specialist. Specimens with a reactive fourth-generation assay result underwent confirmatory testing.

RESULTS

From July 11, 2011, through January 5, 2014, 27,952 HIV screenings were performed for 22,468 patients tested for HIV; 78 (0.28%) had new HIV diagnoses. Of those, 18 (23% of all new diagnoses) were acute HIV infections, and 22 patients (28%) had a CD4 count of less than 200 cells/mL, or an opportunistic infection.

CONCLUSION

HIV testing with a fourth-generation antigen/antibody laboratory test producing rapid results is feasible in an ED. Unexpectedly, nearly one fourth of patients with undiagnosed HIV had acute infections, which would have been more difficult to detect with previous testing technology.

Targeting screening and social marketing to increase detection of acute HIV infection in men who have sex with men in Vancouver, British Columbia

OBJECTIVES

The contribution of acute HIV infection (AHI) to transmission is widely recognized, and increasing AHI diagnosis capacity can enhance HIV prevention through subsequent behavior change or intervention. We examined the impact of targeted pooled nucleic acid amplification testing (NAAT) and social marketing to increase AHI diagnosis among men who have sex with men (MSM) in Vancouver.

DESIGN

Observational study.

METHODS

We implemented pooled NAAT following negative third-generation enzyme immunoassay (EIA) testing for males above 18 years in six clinics accessed by MSM, accompanied by two social marketing campaigns developed by a community gay men's health organization. We compared test volume and diagnosis rates for pre-implementation (April 2006-March 2009) and post-implementation (April 2009-March 2012) periods. After implementation, we used linear regression to examine quarterly trends and calculated diagnostic yield.

RESULTS

After implementation, the AHI diagnosis rate significantly increased from 1.03 to 1.84 per 1000 tests, as did quarterly HIV test volumes and acute to non-acute diagnosis ratio. Of the 217 new HIV diagnoses after implementation, 54 (24.9%) were AHIs (25 detected by pooled NAAT only) for an increased diagnostic yield of 11.5%. The average number of prior negative HIV tests (past 2 years) increased significantly for newly diagnosed MSM at the six study clinics compared to other newly diagnosed MSM in British Columbia, per quarter.

CONCLUSION

Targeted implementation of pooled NAAT at clinics accessed by MSM is effective in increasing AHI diagnoses compared to third-generation EIA testing. Social marketing campaigns accompanying pooled NAAT implementation may contribute to increasing AHI diagnoses and frequency of HIV testing.

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.

The detection and management of early HIV infection: a clinical and public health emergency

This review considers the detection and management of early HIV infection (EHI), defined here as the first 6 months of infection. This phase is clinically important because a reservoir of infected cells formed in the individual renders HIV incurable, and the magnitude of viremia at the end of this period predicts the natural history of disease. Epidemiologically, it is critical because the very high viral load that typically accompanies early infection also makes infected individuals maximally contagious to their sexual partners. Future efforts to prevent HIV transmission with expanded testing and treatment may be compromised by elevated transmission risk earlier in the course of HIV infection, although the extent of this impact is yet unknown. Treatment as prevention efforts will nevertheless need to develop strategies to address testing, linkage to care, and treatment of EHI. Cost-effective and efficient identification of more persons with early HIV will depend on advancements in diagnostic technology and strengthened symptom-based screening strategies. Treatment for persons with EHI must balance individual health benefits and reduction of the risk of onward viral transmission. An increasing body of evidence supports the use of immediate antiretroviral therapy to treat EHI to maintain CD4 count and functionality, limit the size of the HIV reservoir, and reduce the risk of onward viral transmission. Although we can anticipate considerable challenges in identifying and linking to care persons in the earliest phases of HIV infection, there are many reasons to pursue this strategy.

Validation of the Elecsys® HIV combi PT assay for screening and reliable early detection of HIV-1 infection in Asia

BACKGROUND

The Elecsys® HIV combi PT assay was developed to allow earlier detection of HIV infection with increased sensitivity and specificity.

OBJECTIVES

To validate the assay for screening and reliable early detection of HIV-1 infection in Asia.

STUDY DESIGN

Samples tested reflected those routinely screened in Asia and comprised: HIV-1 antigen lysate (25 samples) and antibody (20 samples) dilutions; seven HIV-1 seroconversion panels (46 samples); 39 patient samples from early infection; 183 known-positive sera; HIV-1 p24 antigen sensitivity panel (seven samples); >500 routine clinical samples per center. The Elecsys® HIV combi PT assay was compared with fourth- (ADVIA Centaur® HIV combo, ARCHITECT® HIV combo, Elecsys® HIV combi) and third-generation (VIRONOSTIKA® HIV Uni-Form II Plus O, Zhuhai Livzon Anti-HIV EIA, Serodia® Particle Agglutination) assays commonly used in the region.

RESULTS

Overall, the Elecsys® HIV combi PT showed superior or similar sensitivity to the comparators for detecting all subtypes. The assay correctly identified all positive samples, including those taken soon after infection, and detected seroconversion at a similar or shorter time interval than the comparators. The analytical sensitivity of Elecsys® HIV combi PT for HIV-1 p24 antigen was 0.90 IU/mL, which was lower than reported previously. The assay showed good specificity (99.86%) that was superior or equivalent to the other fourth-generation assays tested.

CONCLUSIONS

These robust data demonstrate the good subtype inclusivity of the Elecsys® HIV combi PT assay and its suitability for screening and reliable early detection of HIV infection in Asia.

ARCHITECT® HIV Ag/Ab Combo assay: correlation of HIV-1 p24 antigen sensitivity and RNA viral load using genetically diverse virus isolates

BACKGROUND

HIV antigen/antibody (Ag/Ab) combination assays represent a significant advancement in assays used for diagnosing HIV infection based on their ability to detect acute and chronic infections. During acute HIV infection (AHI), detection depends on assay sensitivity for p24 Ag.

OBJECTIVE

To directly compare the Ag sensitivity of the ARCHITECT(®) HIV Ag/Ab Combo assay to RNA viral load using cell culture supernatants of virus isolates. HIV-1 isolates allow correlation in the total absence of an antibody response to infection and across genetically diverse HIV-1 group M strains.

METHODS

Thirty-five HIV-1 isolates comprising subtypes A-D, F and G, CRF01_AE, CRF02_AG, and unique recombinant forms were evaluated. Cell-free culture supernatant for each isolate was diluted to four levels and tested in the HIV Combo assay to determine a signal to cutoff ratio and the RealTime(®) HIV-1 assay to quantify RNA. The RNA copies/mL at the HIV Combo assay cutoff was determined.

RESULTS

The median RNA copies/mL at the HIV Combo assay cutoff was 57,900 for individual virus isolates (range 26,440-102,400). A single plot of all the data gave a value of 58,500RNA copies/mL. An analysis of data published for acute HIV infection in human subjects gave a similar result; HIV Combo detected 97% of AHIs with RNA copies/mL > 30,700.

CONCLUSIONS

Based on analysis of virus isolates, the ARCHITECT HIV Combo assay can detect p24 Ag when RNA is above approximately 58,000copies/mL. The correlation of viral load and Ag sensitivity was consistent across genetically diverse HIV-1 group M strains.

Simple diffusion-constrained immunoassay for p24 protein with the sensitivity of nucleic acid amplification for detecting acute HIV infection

Nucleic acid amplification techniques have become the mainstay for ultimate sensitivity for detecting low levels of virus, including human immunodeficiency virus (HIV). As a sophisticated technology with relative expensive reagents and instrumentation, adoption of nucleic acid testing (NAT) can be cost inhibited in settings in which access to extreme sensitivity could be clinically advantageous for detection of acute infection. A simple low cost digital immunoassay was developed for the p24 capsid protein of HIV based on trapping enzyme-labeled immunocomplexes in high-density arrays of femtoliter microwells and constraining the diffusion of the enzyme-substrate reaction. The digital immunoassay was evaluated for analytical sensitivity for HIV capsid protein p24, and compared with commercially available NAT methods and immunoassays for p24, including 4th-generation antibody/antigen combo assays, for early detection of HIV in infected individuals. The digital immunoassay was found to exhibit 2000-3000-fold greater analytical sensitivity than conventional immunoassays reactive for p24, and comparable sensitivity to NAT methods. Assaying serial samples from 10 HIV-infected individuals, the digital immunoassay detected acute HIV infection as early as NAT methods, and 7-10 days earlier than conventional immunoassays. Comparison of assay results between the digital immunoassay and a quantitative NAT method from HIV infected serum exhibited a linear correlation R(2)>0.99. The data indicate that by constraining diffusion of the signal generation step of a simple sandwich immunoassay and enabling the digital counting of immunocomplexes, dramatic improvements in sensitivity to virus can be obtained to match the sensitivity of NAT at a fraction of the cost.

Need for nucleic Acid testing in countries with high prevalence of transfusion-transmitted infections

Introduction. In India, family/replacement donors still provide more than 45% of the collected blood. With increasing voluntary blood donation and the still-prevalent infectious diseases in donors, we need to augment transfusion-transmitted infections (TTIs) testing before use. Our study was aimed to know the seroprevalence of TTIs among the donors of Rajasthan and the need for newer technologies like nucleic acid testing (NAT). Materials and Methods. Enhanced chemiluminescence immunoassay (ECi) was used for detection of HBsAg, anti-HIV, and anti-HCV in donor serum. 50% of the blood units which were negative on ECi were randomly selected and subjected to NAT testing for HBV, HCV, and HIV. Results. The total seroprevalence of TTIs is 2.62%. Of the randomly selected donor units negative by ECi, 8 turned out to be reactive on NAT testing: 4 were voluntary and 4 were family/replacement donors. Combined NAT yield (NAT reactive/seronegative) for HIV, HCV, and HBV was 0.034% (1 in 2972 donations). All the 8 reactive samples were positive for HBV DNA. Conclusion. In countries with a high prevalence of TTIs like India there are likely to be a significant number of window period donations that can be identified by NAT which may be implemented in blood centers allover India with serological testing to provide safe blood and cost alone should not be a deterrent to the government and implementing agencies.