FAQs

CDC developed a new RTRI that can diagnose HIV infection and distinguish recent from long-term infection in a single lateral flow format. Absence or presence of a line is used to determine whether an individual has a recent infection or long-term infection, respectively. These tests are similar in concept to a HIV rapid diagnostic test but includes a third line that detects only long-term infection. Absence of this third line is indicative of recent infection. These tests can be performed in HTS, and results are available within 20 minutes. In contrast, laboratory-based test for recent infection (e.g. LAg-Avidity enzyme immunoassay [EIA]) are conducted in a central laboratory, require collection and transport of a blood specimen, and can take days to process and return results.

Based on RTRI evaluation, a recent HIV infection is one that was acquired approximately within the past 12 months. Although “mean time” for recent infection detection is about 6 months, there is distribution of recent infection around the mean, which can vary from 3 months to >9 months. Therefore, at the individual level, it is appropriate to characterize recent infection as having acquired HIV within the past 12 months.

Persons with recent HIV infection may have a higher viral load and thus be more infectious and likely to transmit HIV. The identification of recent infection provides an opportunity to describe the HIV epidemic, identify ongoing or recent transmission, and intervene to stop further transmission. However, it will also be important to better understand characteristics of persons who are diagnosed with long-term infection as this may inform missed opportunities for HIV testing.

A transmission cluster is a group of HIV-infected persons (diagnosed or undiagnosed) who have a direct epidemiological connection related to recent or ongoing transmission in a population. Transmission clusters should signal a public health response to improve health outcomes and prevent infections by initiating testing activities, link or re-link HIV-positive persons into care, and provide prevention interventions for HIV-uninfected persons in the network.

The proportion of newly diagnosed persons with recent infection will vary by population and setting. Published data are only available from a few European countries where an HIV test for recent infection (TRI) has been incorporated into routine HIV case surveillance. In France, 23% of newly diagnosed HIV-positive persons tested recent, with a higher proportion of recent infections among younger age groups and MSM (Semaille, 2008. Euro Surveillance). In the United Kingdom, 15% of newly diagnosed HIV-positive persons tested recent, and higher proportions were observed among newly diagnosed MSM, at 22% (Aghaizu, 2014. Euro Surveillance). Unpublished data from Nicaragua indicate that 13% of persons testing HIV-positive in 205 sites were recently infected using a RTRI and viral load testing in 2018. Although number of newly diagnosed cases should go down, the proportion testing recent may increase over time as we reach epidemic control due to early diagnosis of HIV infection.

RTRIs are similar to HIV rapid diagnostic tests and can be performed by trained health facility staff within HTS as a supplemental test for persons who are newly confirmed HIV-positive through the national HIV testing algorithm. The test should not be performed by untrained person or individual client.

RTRI technology has been commercialized by two manufacturers (Figure 1) as:
1) Asante HIV-1 Rapid Recency Assay by Sedia Biosciences (Portland, OR) and
2) Swift Recent Infection Assay (RIA) by Maxim Biomedical (Rockville, MD).
Asante Rapid Recency Assay is available as 100 tests or 20 tests per kit. Swift RIA is available as 20 tests per kit. In addition, quality control specimens are available from Maxim that includes three specimens with HIV-negative, recent and long-term status.  

Both RTRIs have undergone extensive in-house evaluation and validation at CDC. In addition, Asante has been evaluated independently in outside laboratories (Maxim Swift evaluation ongoing). In all settings, the test performed well with acceptable criteria for both HIV diagnosis and recent infection detection. 

Figure 1. Rapid Tests for Recent Infection

Asante HIV-1 Rapid Recency Assay
Maxim Recent Infection Assay

Both RTRIs are based on the same principle of using limiting antigen to distinguish recent or long-term infections (LT line) and use the same antigen as LAg-Avidity EIA but in a rapid lateral low format. The performance of the test in distinguishing recent or long-term infection is similar to the LAg assay at normalized optical density (ODn) cutoff of 2.0 corresponding to mean duration of recent infection (MDRI) of 6 months[1],[2].


[1]Parekh B, Detorio M, Shanmugam V, Yufenyuy E, Dobbs T, Kim A, Nkengasong J. Performance evaluation of Asante Rapid Recency Assay for HIV diagnosis and detection of recent infection: potential for surveillance and prevention. Poster session presented at: IAS Conference on HIV Science; 2017 July 23-26; Paris, France. Available at: http://www.ias2017.org/Portals/1/Files/IAS2017_LO.compressed.pdf

[2]Agyemang E., et al. Performance of a novel point-of-care HIV recency test among newly diagnosed pregnant adolescent girls and young women — Malawi, 2017. International AIDS Conference 2018 abstract number THPEC 200, 2018

A RITA is a combination of laboratory tests and laboratory/clinical information used to classify an HIV infection as recent or long-term infection. To screen out false recent results of individuals on ART or elite controllers, viral load testing can be used in combination with the RTRI for final confirmation of recent infection status. Persons who test recent on the RTRI should have a blood specimen collected for viral load testing, if possible (see next question). Those who test recent on the RTRI and have a viral load ≥1,000 copies/mL will be considered as a confirmedrecent case (Figure 2).

Figure 2. Recent Infection Testing Algorithm with Viral Load Testing in Routine HIV Testing Services 

If a client tests recent on the RTRI, further confirmation is advised, if feasible, through viral load testing. If returning RTRIresults to clients, the counselling session should emphasize that a recent test result is preliminary and requires additional testing for confirmation and that the final confirmed test result will be returned once available. Note that a long-term test result on the RTRI does not require confirmation and can be returned during the counselling session as the final result. Implementation of the RITA with viral load testing is not required in settings where viral load testing is not readily available. Countries should determine whether viral load testing for all individuals testing recent on the rapid test is reasonable in their context.

The RTRI was developed for the detection of recent HIV-1 infection. The long-term line of the test includes only HIV-1 specific antigen. Therefore, the RTRI cannot be used to detect recent infections among HIV-2 positive persons.If used in geographical areas where HIV-2 is prevalent (or if HIV-2 infection is suspected), it is important to perform type-specific diagnosis using Geenius or similar test before final recent infection classification can be made. However, the diagnostic verification line or test line does detect both HIV-1 and HIV-2.

Similar to other incidence assays, the RTRI may misclassify some persons as recent (e.g., absence of long-term line on RTRI) who have had HIV for a longer duration of time. The proportion false recent (PFR) may be affected by various factors listed below. To control for these factors, the addition of viral load testing in a RITA can minimize false-recent cases but may not capture all false-recent cases.

  • PLHIV on ART: All persons on ART should be excluded from RTRI testing. A proportion of persons on ART will misclassify as “recent” due to declining antibody avidity when viral load is suppressed for longer duration. If a person has a lapse in ART or develops drug resistance and experiences viral rebound, he/she could test as recent on the RITA.
  • Elite Controllers: Some persons with long-term infection may test recent in the absence of ART even after years of infection due to naturally low viral load resulting in low-avidity antibodies. Though this is a rare occurrence (<1% of HIV-infected persons), the proportion of elite controllers is expected to be higher in older epidemics than younger epidemics. 
  • HIV-2 positive persons:As described earlier, the HIV diagnostic verification line does not distinguish between HIV-1 and 2 but includes both antigens. The long-term line includes only HIV-1-specific antigen, to which HIV-2 antibody would not bind. Therefore, all HIV-2 positive persons will be classified as HIV-1 recent infection irrespective of duration of their infections. If the RTRI is used in geographical areas where HIV-2 is prevalent or if HIV-2 infection is suspected, it is important to perform type-specific diagnosis before final recent infection classification can be made. Dually infected persons can be tested on RTRI with interpretation similar to HIV-1 infected persons.
  • HIV-1 subtypes: Misclassification may vary by HIV-1 subtypes and may be higher in certain subtypes than others (e.g., clade D virus). Ongoing evaluations are being conducted to confirm the PFR among persons infected for >1 year across different subtype infections. However, the impact of subtype variation should have little or no impact for the intended use of the assay. 

No. The RTRI does not detect acute HIV infection before antibody response. Persons who have acute HIV infection do not have HIV antibodies and will test HIV-negative by a national HIV testing algorithm comprised of HIV antibody tests.  Thus, in countries where the national HIV testing algorithm includes HIV antibody tests, persons with acute infection will not be detected and will not be referred for recent infection testing by the RTRI. 

No, the test should not be performed using DBS. The RTRI should be performed using whole blood or plasma.

This may happen, but it will be very rare. If it does occur, the RTRI should be repeated and the results recorded. The national HIV testing algorithm is always the final HIV result. The quality of HIV testing should be reviewed and ensured.  

A faint third line (long-term line) should be interpreted as long-term. The RTRI is not a diagnostic test. Different interpretations of a faint third line (long-term line) are acceptable. The third line (long-term line) measures the evolving antibody avidity and a person could truly be at the transition between recent and long-term infection and therefore the test may show a faint third line (long term line). Neither interpretation is wrong, keeping in mind that HIV status does not change irrespective of recency status. 

The primary objective of this surveillance system is to monitor recent infections among newly diagnosed PLHIV and identify, in real-time, geographic areas with high probability of recent transmission. Identification and investigation of potential recent transmissions will enable the public health response to be efficient and targeted to those at highest risk of transmitting and acquiring HIV infection. At the population-level, data from the surveillance system will be used to monitor trends in recent infection among newly diagnosed PLHIV by person, place, and time to inform epidemic control efforts.

First, only newly diagnosedHIV-positive persons should be tested for recent infection. If the person was diagnosed previously and/or on ART, they should not be tested for recent infection. To meet the objectives of a recent infection surveillance system, a census of newly diagnosed PLHIV is required to identify any and all recent transmission in area under surveillance. However, the test should be performed only on persons aged 15 years and older.  Most HIV-positive cases <15 years of age are likely to have been acquired perinatally and not likely to be newly infected.

Since national coverage of the surveillance system may not be feasible in the first year of implementation, COP 2018 funding should prioritize saturation of PEPFAR focus districts. Since the objective of this surveillance system is to serve as a signal for trends in new infections, all new diagnoses should be captured to the extent possible.

Persons using PrEP who test HIV-positive are eligible for testing for recent infection.  PrEP may affect development of HIV antibodies but if the person is identified as HIV-positive on routine diagnostic tests, they should be tested on RTRI. To the extent possible, information on PrEP history should be captured.

A data analysis template has been developed for countries to consider including in their RTRI data analysis plans. The template includes table shells for the HTS_RECENT MER indicator by disaggregates; descriptive analysis of recent infection by select demographic characteristics and HIV-positivity yield among partners by index case RTRI result; complex analysis including identification of risk factors for recent infection and geospatial analysis.  

Although the primary objective of the recent infection surveillance system does not include HIV incidence estimation, surveillance data may be used to estimate national and sub-national HIV incidence as a secondary objective. Importantly, the system will only include populations that access HIV testing services, thus complex weighting will be required to adjust for individual testing probabilities and missing information for populations that do not access testing. Additional data are needed for HIV incidence estimation: number receiving HIV testing, number of HIV negatives, number of known HIV positives, and number testing recent by RITA.

Recent infections indicate ongoing HIV transmission and early HIV diagnosis. Local context is critical to consider in the interpretation of trends, including: the proportion of PLHIV diagnosed and on ART, HIV program’s HIV testing efforts, and persons’ HIV testing patterns. A change in the number or proportion of persons testing recent may not always mean a change in HIV incidence. For example, an increase in the proportion testing recent may mean: new HIV infections are increasing, program has increased testing efforts and diagnosed more PLHIV early, and/or persons at risk are appropriately retesting frequently.

Countries that are currently implementing HIV recent infection testing in routine HIV testing services are Malawi, Zambia (ANC); Rwanda, Ethiopia, Guatemala, Nicaragua, Honduras, and El Salvador (HTS); Rwanda (HTS), and Vietnam (HTS). Best practices from the Central America pilot is publicly available on the PEPFAR Solutions Platform (Emerging Technologies).  

There are no concerns for use in PEPFAR given that the test is not used for clinical management nor will standard of care for newly diagnosed persons change based on recent infection status. Moreover, the new test is not part of the national testing algorithm. It will be used for real-time surveillance of new infections among persons who are confirmed HIV-positive per national testing guidelines and response efforts. There are plans for the RTRI to go through the WHO prequalification process for HIV diagnosis and recent infection testing, though this process is expected to take some time since currently recent infection testing is not part of the WHO prequalification portfolio.

Some country regulating bodies may require registration of the RTRI prior to routine use, and registration requirements may differ based on the intended use (e.g., research vs. routine service). We recommend that you review your country’s registration requirements well ahead of planned implementation (including timeline for registration, costs of registration, and technical requirements) to ensure there is sufficient time to complete this process before the activity is rolled out. In some countries, a waiver of registration may be granted for research purposes.

Given that the test has been extensively evaluated and validated in CDC and other independent laboratories (e.g., NICD, South Africa), in-country validation of the RTRI is notrequired. Validation of this test requires well-characterized bank of specimens with known HIV status (positive or negative) and recent infection status (recent or long-term) which most countries lack. The HQ team cannot support any further validation of the RTRI in country in terms of protocol development, reagent and kits, or data analysis. However, we will continue to assist in review of programmatic data generated during implementation to monitor performance of the test and success of implementation. HQ can also provide a verification panel and assist with in-country verification of the RTRI if needed.      

Yes. Because of the “research use” label of the RTRI, any CDC-funded activities that include the RTRI must be implemented under a research protocol and will require local IRB approval. Protocol templates for HIV recent infection surveillance are available for countries to adapt and reference for their local institutional review board (IRB) protocol submissions. Country teams are encouraged to submit their protocols to the local IRB at least 6 months prior to planned implementation to ensure there is sufficient time to obtain IRB approval (or Ministry of Health approval, if local IRB review is not indicated) and CDC research approval before the activity begins. Note that Ministries of Health may include recency testing as part of routine program activities per national HIV guidelines and policy, and therefore not require local IRB approval for the activity. In this case, if any portion of the activity is funded by CDC, a CDC research protocol is still required, along with documentation of MOH approval of the activity. Under a research designation, all or part of the consent process may be waived with opt-out options, if the activity meets criteria for being minimal risk to participants as per 45 CRF 45.116(f)(3).

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