Highlights From the 2019 HIV Diagnostics Conference: Optimizing Testing for HIV, STIs, and HCV

Since 2005, the HIV Diagnostics Conference has served as a central platform for fostering collaborations and partnerships among attendees who are involved in all aspects of HIV testing. The conference provides an open forum where attendees present and exchange ideas, review data on newer test technologies and algorithms, preview innovative testing methodologies and technologies, and present best practices related to testing, including how it relates to linkage to care, treatment, and prevention services. This approach has proven to be effective to encourage the advancement of HIV testing technology and strategies used in the US.

The 2019 conference, held in Atlanta, Georgia, on March 25–28, welcomed almost 400 attendees. This year’s conference included 3 themes that framed the dialog and discussion. First, numerous conference discussions were related to the possible reclassification of HIV and hepatitis C diagnostic tests to a different level of regulatory oversight and the potential impact of these changes. This process, led by the Food and Drug Administration (FDA), began with advisory committee meetings¹ in March 2018 for HCV and July 2018 for HIV. During the conference, FDA staff presented an update on the process² and chaired a feedback session on the topic along with staff from the Centers for Disease Control and Prevention (CDC). Second, the introduction in 2019 of the federal initiative to End the HIV Epidemic (EHE)³ highlighted the importance of having the latest diagnostic tools to improve the availability of, and access to, routine HIV testing,^4,5 which was a key component of meeting discussions. The third element to influence the organization of the meeting was the expansion of the conference agenda to include STIs and hepatitis C diagnostic testing in laboratories, public health programs, and clinical practice.⁴ This is particularly relevant because reported cases of chlamydia, gonorrhea, and syphilis have increased sharply over the past 5 years⁶ and STIs are a strong indicator of HIV risk.⁷ Furthermore, among people with HIV infection, 25% are coinfected with HCV, and among people who inject drugs, nearly 75% of persons diagnosed as having HIV infection are coinfected with HCV.⁸

RECLASSIFICATION OF HIV AND HCV DIAGNOSTIC TESTS

The FDA classifies devices into regulatory classes based on the risk associated with their use. Most infectious disease diagnostic tests are class II (moderate risk) devices. To enter the US market, they are subjected to a marketing clearance application based on proving that the devices are “substantially equivalent” in safety and effectiveness to another legally marketed device (also known as a predicate). Currently, both HIV and hepatitis C diagnostic tests are classified as class III (high risk) devices, and as such, they need to undergo a premarket approval application process to be marketed in the US. Premarket approval applications require data from clinical trials conducted to prove the safety and effectiveness of the device for each intended use, including all specimen types, which can take a long time and be quite costly.

At the time of their discovery, HIV and HCV infections each posed a high risk of illness or death, and neither virus had effective treatment options, supporting a high-risk classification of diagnostic tests for these pathogens. In addition, in the early days of the HIV epidemic, tests often had a dual claim for diagnosis and blood screening, which requires the highest level of regulatory oversight. The push for reclassification of HIV and hepatitis C diagnostic tests from class III to class II comes at a time with a curative therapy for hepatitis C and highly effective antiretroviral therapy for HIV. Furthermore, over time there has been a decrease in the number of tests that have intended use claims for both diagnosis and blood screening, and there are considerable data on HIV and hepatitis C diagnostic tests that can be used as predicate devices for a class II classification. The reclassification aims to reduce the financial and time burden of the approval pathway to facilitate the introduction of new and innovative devices into the US market.

The reclassification proposal presented by FDA in March of 2018 was for down classification of antibody tests for the detection of immunoglobulin G antibodies to hepatitis C, qualitative and quantitative nucleic acid–based hepatitis C tests for the detection and/or quantitation of HCV RNA, and nucleic acid–based HCV genotyping tests. Proposed special controls (specific performance criterion beyond demonstration of equivalence) includes a sensitivity point estimate that must be at least 99%, with a lower limit of the 2-sided 95% confidence interval of at least 95%, and a specificity point estimate that must be at least 98.5%, with a lower limit of the 2-sided 95% confidence interval of at least 95%. In July 2018, discussion of HIV test reclassification was limited to point-of-care (POC) and laboratory-based serological and molecular tests for the diagnosis of HIV and did not include HIV self-tests or quantitative HIV nucleic acid tests (NATs). Furthermore, the FDA included special controls for class II HIV tests that are more restrictive than the controls proposed for hepatitis C tests. During the conference, attendees shared concerns regarding the stricter special controls for HIV, as they could translate into a large sample size requirement for clinical trials and a higher associated cost potentially decreasing the benefit of reclassification. During the feedback session, the FDA was presented with a request from attendees and the CDC to reconsider the special control requirements for HIV to be consistent with those proposed for hepatitis C tests. To support this, CDC staff reiterated their willingness to continue conducting performance evaluations and comparisons of tests that come to the US market. Although quantitative HIV NATs were not included in the reclassification process, it has been stated by FDA staff that additional meetings would not be needed for FDA to reclassify them. The FDA also reiterated their willingness to work with manufacturers seeking to add a diagnostic use claim to their quantitative HIV NATs before the reclassification process is concluded. Although the FDA presented on the proposed reclassification on the first and last days of the conference, the implications of this change were discussed in multiple conference sessions.

LABORATORY HIV TESTING ALGORITHM

Several conference presentations described data on the performance of the newer tests in the currently recommended laboratory HIV testing algorithm or described advances that support this algorithm.^9–12 The CDC and the Association of Public Health Laboratories support a shared service model that provides US public health laboratories access to testing with a qualitative HIV-1 NAT¹³ and has recently expanded its service by offering testing with a HIV-2 NAT to resolve HIV-2 indeterminate or HIV indeterminate results.¹⁴ This service expansion was built on experience testing with a quantitative HIV-2 NAT as a part of the clinical care of HIV-2–infected patients from New York State.¹⁵

The federal EHE initiative emphasizes the need for routine HIV testing in clinical settings and increased testing frequency among people with ongoing risk to diagnose HIV as soon as possible after infection. Prompt diagnosis followed by linkage to care and treatment during acute or early HIV infection is necessary to interrupt transmission to others during a time of high levels of viremia. Therefore, it is encouraging that the widespread adoption of the laboratory HIV testing algorithm has increased detection of acute HIV infection (AHI),^16,17 with an analysis of national data¹⁶ showing that detection of AHI was at least 6 times as high (3.1%) as the yield with the previously used algorithm (0.5%). Efforts to increase testing frequency could have also contributed to the observed increase in AHI diagnoses among new HIV diagnoses from 4.9% in 2010 to 13.6% in 2017 in New York City.¹⁷

The laboratory HIV testing algorithm includes the recommendation for follow-up with an HIV-1/HIV-2 antibody differentiation testing after a reactive screening result. However, an examination of national surveillance data found extremely low numbers of HIV-2 diagnoses despite a significant increase in the use of HIV-1/HIV-2 antibody differentiation tests.¹⁸ Similarly, an analysis of clinical data reported in this journal issue by Wesolowski et al¹⁹ supported these findings and prompted discussion among attendees about the need for an HIV-1/HIV-2 antibody differentiation step in the US algorithm. Data exploring an alternative algorithm where a reactive antigen/antibody screening assay is followed by a quantitative HIV NAT^20,21 led to considerations for reversing the second and third steps of the algorithm. Conducting HIV or HCV NAT after serology,^20,21 especially when antibody screening and NAT confirmation are performed with the same sample, raised questions about the potential for contamination. This did not seem to be a problem in one analysis of paired serologic and molecular testing of the same sample also reported in this issue.²²

IMPROVING ACCESSIBILITY OF HIV TESTING

Making HIV testing more accessible and engaging people with HIV in treatment are 2 important components of the federal EHE initiative. POC HIV tests have proven to be a convenient and effective option in settings where more sensitive laboratory-based testing is not possible or practical, with the added benefit of providing expedient results. Understanding the inherent limitations²³ and the performance characteristics of POC tests when using unprocessed whole blood or oral fluid specimens²⁴ can help programs design a successful rapid testing program. In this regard, Antle²⁵ described a successful approach to HIV outreach testing that combines POC testing and prompt delivery of results with the use of client navigators to provide onsite linkage to care and prevention services. The implementation of a 2-test rapid testing algorithm, also known as rapid-rapid algorithm, is another approach that can reduce the time to diagnose HIV and potentially shorten the time between HIV testing and engagement in care.^26,27 The feasibility of this method was demonstrated in low-prevalence settings,²⁶ as well as among a high-risk population, in the context of anonymous venue-based testing and linkage.²⁷

Novel uses of existing tools to improve access to testing include the distribution of rapid HIV self-tests, the self-collection of samples for laboratory testing, and the use of web-based or mobile technologies to engage populations that might otherwise not be tested.^28,29 At least 3 different HIV self-tests are approved for sale and distribution in Europe and have received the Conformité Européenne CE; (French for European Conformity) marking. By contrast, in the US there is only one FDA-approved HIV self-test. However, data presented at the conference showed promising results on the performance and ease of use of an FDA-approved rapid test repackaged for self-test use.³⁰ Nevertheless, not including self-tests in the reclassification process of HIV tests might prolong the approval process for additional HIV self-tests and delay their entry into the US market. A discussion panel on self-testing and self-collection of samples for HIV and STIs²⁹ highlighted some opportunities provided by these modalities. Data presented from a CDC-funded 2-arm randomized clinical trial³¹ evaluating the use and impact of providing HIV self-tests to Internet-recruited men who have sex with men showed increased awareness of HIV infection in the self-testing arm. An example of the implementation of a local HIV self-testing program was provided by the New York City Department of Health and Mental Hygiene, which incorporated an HIV self-testing program^29,32,33 into their existing suite of testing approaches. A web-based ordering program (iwantthekit.org) that provides self-collection kits to collect vaginal, penile, and/or rectal samples for STI testing now also provides free HIV self-tests. Users of this service reported great acceptability of self-collection and self-testing and provided positive feedback about the program overall.²⁹

Another potential method for the self-collection of samples for laboratory testing is with dried blood spots (DBS). The only FDA-approved protocol to test DBS samples for HIV does not follow the current laboratory HIV testing algorithm and includes the use of 2 tests that are not widely available, the Avioq HIV-1 Microelisa System (Avioq, Inc.), followed by a Western Blot as a confirmatory test. Furthermore, the manufacturing of the only FDA-approved DBS self-collection kit for HIV testing, the Home Access HIV-1 Test System (Home Access Health Corporation), was discontinued in 2019. Promising data were provided in several presentations describing feasibility and performance evaluations of modified protocols that allow for the use of other assays that follow the laboratory HIV testing algorithm with self-collected³⁴ or tester-collected DBS.^35,36 Kim et al.³⁷ described the feasibility and acceptability of using DBS collection administered by health care workers for reaching Canada’s indigenous communities and the validation of HIV and HCV testing using DBS samples. This successful program highlights a potential opportunity to use this strategy in the rural US and other underserved communities.

BUILDING MOMENTUM FOR THE AVAILABILITY OF MOLECULAR TECHNOLOGIES

Several molecular technologies in use outside the US could prove to be valuable tools for HIV testing efforts if, and when, they become available.³⁸ In the US, only one qualitative HIV-1 NAT is approved for diagnostic use. Quantitative HIV NATs are indicated for the monitoring of HIV disease progression and are not currently approved for diagnostic use in the US, despite performance data supporting this intended use.^{20–22,39–42} This situation leaves laboratories providing both diagnostic and monitoring services with the choice to either maintain 2 methods (a qualitative HIV NAT for diagnosis and a quantitative HIV NAT for disease monitoring) or to perform an in-house validation of a quantitative HIV NAT for diagnostic use. One hospital laboratory presented on a validation of a quantitative HIV NAT (FDA-approved for HIV-1 monitoring only, CE-marked for HIV-1 diagnosis and monitoring) so it could be used for diagnosis.³⁹ Once validated, its implementation not only was a viable option for both HIV-1 diagnosis and monitoring of their patient population but also allowed for the repurposing of 13% (600 sq ft) of their laboratory space and reduced hands-on-time for staff performing HIV diagnostic testing.³⁹

Quantitative or qualitative POC NATs, including those used with unprocessed whole blood, are currently only available outside the US.^{39–41,43,44} POC NATs have been successfully evaluated and implemented in Kenya for early diagnosis of HIV in infants.⁴³ At the conference, the performance evaluation of one POC HIV NAT showed that it can be run on unprocessed whole blood to detect HIV-1 RNA and/or DNA. This assay shows promise as evidenced by the high degree of concordance with other HIV viral load assays.⁴¹ Violette et al.⁴² confirmed the high specificity of a POC HIV NAT platform used in an STI clinic in Seattle, suggesting that POC HIV NATs have the potential to improve HIV prevention by having a role in preexposure prophylaxis (PrEP) initiation and monitoring among people who are presumed to be HIV negative. Other opportunities created by qualitative and quantitative HIV POC NATs mentioned at the conference included the resolution of discordant results in rapid-rapid algorithms, POC diagnosis of AHI, and real-time clinical monitoring of patients receiving HIV antiretroviral therapy.³⁹

The FDA approval or clearance of these molecular technologies, if done expeditiously, could be used to favorably affect the outcomes of the federal EHE initiative. However, it will be important to determine how to best integrate POC HIV NATs and quantitative HIV NATs that can be used for both diagnosis and monitoring into the laboratory HIV testing algorithm.^38,39

OTHER EMERGING TESTING ISSUES

A variety of emerging issues related to HIV testing were also presented. First, testing in the context of PrEP introduces the potential for new opportunities and challenges.³⁸ For example, implementation of CDC PrEP guidelines has led to an increase in STI testing⁵ which may lead to an STI control opportunity.⁷ Increased uptake of HIV testing and subsequent PrEP initiation might increase the number of ambiguous or false HIV test results due to the low positive predictive value of all HIV tests among people using PrEP.⁴⁵ These situations could be resolved promptly with NATs performed on whole blood^44,46 or testing for cell-associated virus to overcome the possibility of delayed seroconversion and minimize delaying a possible HIV diagnosis.

Second, within the context of the EHE initiative, there might be renewed interest in the use of recency assays to differentiate persons who have been infected in the last year (true incident infections) from persons who have been infected for several years. Preliminary evaluation data of a lateral flow rapid recency assay showed acceptable performance for its use in population level incidence surveillance.⁴⁷ However, having an FDA-approved recency assay available in the US will require guidance to establish a standardized definition of “recency” and proposals outlining the data that will be needed to validate a recency claim.

Third, effectively achieving sustained viral suppression could be aided by a molecular technology that combines the qualitative detection of virus expression to assess viral suppression with the detection of drug resistance using a simplified multiplex PCR method.⁴⁸ This technology has been shown to simplify the process for monitoring both viremia and resistance in resource-constrained HIV care systems. This combination of detection of both viremia and resistance could become an invaluable tool for the US if it evolves into a POC NAT format.

Finally, Rowlinson et al.⁴⁹ demonstrated the feasibility of using next-generation sequencing for HIV genotyping and resistance determination in a public health laboratory. More widespread use of next-generation sequencing technology in both clinical and public health laboratories has the potential to improve appropriate antiretroviral therapy initiation, detection of molecular clusters, and transmission pattern identification. However, this promising approach will require modernizing and coordinating laboratory and surveillance infrastructure to ensure its effectiveness.

INTEGRATED TESTING FOR MULTIPLE PATHOGENS

Increasing rates of STIs (syphilis, gonorrhea, and chlamydia) nationally, increasing coinfection of HIV with STIs and hepatitis C, and overlapping risks for all 3 pathogens highlight the need for better integration of HIV, STI, and hepatitis C testing.^50,51 Approximately half of public health laboratories surveyed by the Association of Public Health Laboratories in 2017 report conducting both HIV and hepatitis C testing,^4,50,52 where 66% of health departments supporting HIV testing report also supporting hepatitis C testing according to the 2019 National HIV Prevention Inventory Survey.^50,53 An example of integrated testing was presented by the North Carolina Department of Health and Human Services, where they leveraged the existing HIV prevention infrastructure to implement risk-based hepatitis C testing throughout the state.⁵⁴ Similarly, the Massachusetts Department of Public Health and the Kentucky State Public Health Laboratory implemented integrated, laboratory-based HIV, STI, and hepatitis C testing for publicly supported agencies.⁵⁰

Integrated testing in clinical settings has the potential to enhance the efficiency of case finding and to improve linkage to care. This approach requires coordination within the health care setting and stakeholder investment, and a focus on sustainability to achieve success.⁵⁰ As described by Larios et al. in this issue of the journal, researchers from the emergency department in one hospital in Miami-Dade County, Florida, responded to a syphilis outbreak and successfully averted cases of congenital syphilis by enhancing their routine HIV/HCV infection testing model with a testing algorithm to test high-risk, HIV-negative patients for syphilis.⁵⁵

Outside the laboratory, integrated testing can take the form of a multiplex rapid test, such as one that detects HIV and syphilis.^56,57 However, no such test is currently FDA-approved for use in the US. Once approved, multiplex rapid tests could be an important addition to the diagnostic toolbox for multiple pathogens. Compared with currently available rapid tests, they can potentially expedite the screening process by providing simultaneous results for multiple pathogens with one test and optimize workflow by using a single sample. This in turn facilitates more timely access to testing for multiple pathogens in remote or resource-limited settings, where quality and timely medical care can be challenging.^7,56

CONCLUSIONS

Discussions during the conference revolved around the major themes of reclassification of HIV and hepatitis C diagnostic tests, the relevance of the conference to the EHE initiative, and the integration of HIV, STI, and hepatitis C testing to further increase test accessibility and effectiveness.

The EHE initiative’s emphasis on diagnosing all people with HIV as early as possible renewed determination among attendees to continue supporting accessible, high-quality HIV testing. In this regard, the collaboration between laboratories and testing programs⁵⁸ will be of utmost importance as different testing strategies are implemented in the first 5 years (phase I) of the EHE initiative in the geographic hotspots accounting for more than half of new HIV diagnoses in 2016 and 2017.³ The guidance and support provided by laboratories is essential for the development of strong testing programs to maintain high quality in all testing modalities, from laboratory-based molecular testing to self-testing in the client’s home.

However, additional HIV-1 and HIV-2 antibody assays, quantitative and qualitative POC HIV and HCV NATs, quantitative HIV and HCV NATs with an intended use for diagnosis, HCV core antigen or HCV POC NAT tests, HIV self-tests, and HIV recency assays will be needed to end the HIV and HCV epidemics in the US. We anticipate that the reclassification of HIV and hepatitis C diagnostic tests to class II devices will encourage the introduction of new technologies in the US. Future conferences will continue to collect and disseminate data to support modifications to the HIV and hepatitis C testing algorithms and continue to focus on diagnosing HIV, STIs and hepatitis C as early as possible to effectively link infected persons to care and treatment and those testing negative to appropriate prevention services.