A transmission hotspot 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 hotspots 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.

If a client tests RTRI recent, VL is advised, if feasible. If returning RTRI results to clients, the counselling session should emphasize that a RTRI recent test result is preliminary that requires VL and that the final RITA result will be returned once available. Note that a RTRI long-term result does not require VL testing 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.

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. A generic protocol template for HIV recent infection surveillance is 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 local IRB approval 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).

Given that the test has been evaluated and validated in ILB/CDC and other independent laboratories (e.g., NICD, South Africa), in-country validation of the RTRI is neither required nor recommended. 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), including longitudinal panels from seroconverting persons, which most countries lack. The HQ team cannot support any further validation of the RTRI in country.

However, we will continue to assist in review of programmatic data generated during implementation to monitor performance of the test and progress of implementation. HQ can also provide a verification panel and assist with in-country verification of the RTRI, if needed.

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.

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. 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.

The primary objective of using RTRI in HTS settings is recent infection surveillance to identify new infections in real-time for targeted prevention and accelerate epidemic control. It is not intended nor ideal for estimation of HIV-1 incidence because: 1) population being tested in HTS setting is not representative of all individuals at risk and not appropriate for estimating incidence, 2) RTRI tests are performed by several testers and results are interpreted visually resulting in less accuracy compared to lab-based LAg-Avidity EIA. Therefore, we do not recommend use of RTRI data for estimation of incidence. Well planned surveys, such as population-based national HIV surveys, ANC surveys, or key-population surveys with appropriate sampling design are best suited for estimation of incidence, which permits collection and testing of specimens in the central laboratory using LAg-Avidity EIA.

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; and more complex analysis including identification of risk factors for recent infection and geospatial analysis.

Persons using PrEP who test HIV-positive (new diagnosis) 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.

The primary objective of this surveillance system is to monitor recent infections among newly diagnosed PLHIV and identify, in real-time, specific population and geographic locations with high probability of recent transmission.

Identification and investigation of populations and geographic locations with 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 cases by person, place, and time to inform epidemic control efforts.

Any visible line, even if weak, should be interpreted as present. The long-term line measures the evolving antibody avidity and a person could truly be at the transition point between recent and long-term infection. In this case, the test may show a faint long-term line which may be interpreted differently by different testers. Neither interpretation is wrong, keeping in mind that HIV status does not change irrespective of recency status. Recency classification is for surveillance purposes and is not used for diagnosis or clinical management.

Although this may happen, it should be very rare. In rare cases when it does occur, you may take the following steps: 1) repeat the national algorithm to confirm HIV-positive status (if retesting for verification not done), and 2) if confirmed HIV-positive, RTRI should be repeated and the results recorded. Irrespective of RTRI results, the national HIV testing algorithm is always the final HIV result. It is important to review inconclusive results in the context of total number of HIV- positives tested. From the review of >60,000 HIV-positive samples tested by Asante in multiple countries, almost 99.8% were confirmed as HIV-positive and classified either as long-term or recent with only 0.2% with inconclusive results.

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

No. The RTRI does not detect acute HIV infection before antibody response. Persons who have an acute HIV infection do not have HIV antibodies and will test HIV-negative by a national HIV testing algorithm based on HIV antibody tests. Thus, in countries where the national HIV testing algorithm is based on antibody detections, persons with acute infection will not be detected and will not be referred for recent infection testing by the RTRI. In countries using both Ag/Ab combo tests (e.g. Determine Ag/Ab Combo), only antibody positive specimens should be referred to RTRI.

Yes. As pointed out earlier, individuals can transition from recent to LT status at varying time periods (3 to >9 months) after infection. This means some individuals who transition early but are still within 12 months of infection will classify as LT. The assay is designed to identify individuals who are still in “recency” status with weak antibodies but cannot identify those who may have transitioned to LT status. However, this individual-level misclassification is less consequential for recent infection surveillance, which uses RTRI to help detect trends in recent infections at the population-level.

Similar to other incidence assays, the RTRI may misclassify some persons as recent who have had HIV for a longer duration of time. The proportion false recent may be affected by factors such as duration of ART or weak antibody development among elite controllers. The addition of viral load testing in a RITA can minimize false-recent cases as stated earlier.

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 a similar test before final recent infection classification can be made. However, the diagnostic verification line of Asante does detect both HIV-1 and HIV-2.

Recency classification can also be improved by additional considerations such as advanced HIV disease, low CD4, prior HIV diagnosis and prior/long-term ARV use or detection, if available. However, if an HIV diagnosis and ARV initiation occurred in the previous 4 weeks, this should not affect recency classification because it takes more than 4 weeks for ARVs to affect antibody avidity.

A RITA is a combination of laboratory tests used to classify an HIV infection as recent or long- term. RITA helps to reduce false recent classification when individuals are on ART or elite controllers. If a client tests recent on the RTRI, viral load (VL) testing should be conducted to improve accuracy of classification. The addition of VL reduces potential false recent cases due to extended ART or weak antibody responses in elite controllers.

Viral load testing is most useful in combination with the RTRI for final determination of recent infection status. Persons who test recent on the RTRI (RTRI-recent) should have a blood specimen collected for viral load testing. Those who test recent on the RTRI and have a viral load ≥1,000 copies/mL should be classified as RITA-recent (Figure 2).

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

A proportion of persons on ART will misclassify as “recent” due to declining antibody avidity when viral load is suppressed for longer duration. Similarly, some elite controllers may be misclassified due to weak immune response because of low viral load. Addition of VL in RITA helps exclude persons on ART already or are elite controllers.

Both RTRI and LAg-Avidity EIA, developed in ILB/CDC, use the same gp41 multi-subtype protein and are based on the same principle of using limiting antigen to distinguish recent from long-term infections. However, the LAg-EIA is a laboratory-based assay requiring specialized equipment while RTRI is a rapid test in lateral flow format. The performance of RTRI in distinguishing recent from long-term infection is similar to the LAg assay at normalized optical density (ODn) cutoff of 2.0 corresponding to the 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

Currently RTRI technology has been commercialized by one manufacturer as Asante HIV-1 Rapid Recency Assay (Sedia Biosciences, Portland, OR; www.sediabio.com). Asante Rapid Recency Assay is available as 100 tests or 20 tests per kit. Asante Rapid Recency Assay has undergone extensive in-house evaluation and validation in CDC. In addition, Asante has been evaluated independently in other laboratories. In all settings, the test performed well with acceptable performance for both HIV diagnosis compared to EIA/WB algorithm and recent infection detection, compared to LAg-Avidity EIA. 

Figure 1. Rapid Tests for Recent Infection [Asante HIV-1 Rapid Recency Assay]

Asante HIV-1 Rapid Recency Assay

C=control line, V=positive verification line, LT=long-term line

The International Laboratory Branch (ILB)/CDC is working with additional manufacturers to transfer this technology successfully. When RTRI kits from new manufacturers are validated and approved, additional notification will be shared.

RTRIs can be performed by trained health facility staff within HTS as an additional test for persons who are newly diagnosed as HIV-positive through the national HIV testing algorithm. The test should not be performed by untrained person or individual client.
The proportion of newly diagnosed persons with recent infection will vary by population, setting and over time. Published data are only available from a few European countries where an HIV test for recent infection 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. As stated earlier, these proportions are expected to change with time.
This proportion may be affected by the fraction of individuals testing HIV-positive who are in fact re-testers and may not be “newly diagnosed.” Current data from countries implementing routine recent infection surveillance, suggest that as many as 30%-50% of HTS clients may be re- testers. Re-testers who go undetected as such, can elevate the denominator and can reduce proportion classified as recent substantially. Appropriate pre-test counseling, and if available, unique ID and case surveillance systems can identify re-testers who should not be tested with RTRI and thereby improve accuracy of recent infection surveillance.
Persons with recent HIV infection may have a higher viral load and ongoing high-risk behavior. Therefore, they are more likely to transmit HIV. The identification of recent infections provides an opportunity to identify and characterize populations with ongoing transmission, understand transmission dynamics, and develop targeted public health interventions to stop further transmission. This approach can accelerate epidemic control when recent infections are detected through surveillance among routine HIV programs and prompt real-time public health response. It is also important to better understand characteristics of persons who have long-term infections as this may inform missed opportunities for HIV testing and treatment.
Based on evaluation of a commercialized RTRI (Asante), a recent HIV infection is one that was acquired approximately within the past 12 months with a mean duration of 6 months. Although “mean time” for recent infection detection is about 6 months, there is a distribution around the mean, which can vary from 3 months to >9 months. Therefore, at the individual level, it is appropriate to interpret recent infection as having acquired HIV within the past 12 months.

The Centers for Disease Control and Prevention (CDC) developed a new rapid test that can simultaneously diagnose HIV infection and distinguish recent from long-term infection in a simple lateral flow format. This test is similar to a HIV rapid diagnostic test but includes an additional line that detects only long-term infection. Absence or presence of the third line is indicative of whether an individual has a recent infection or long-term infection, respectively. Due to its simplicity, this test can be performed in HTS and results are available within 20 minutes.

For further questions or assistance, please contact Recency Surveillance Co-Leads:
Bharat Parekh, bsp1@cdc.gov
Monita Patel, cwa3@cdc.gov
Helen Dale, ffg4@cdc.gov

  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