HIV “recency tests” used to estimate new cases and monitor HIV spread
A test that indicates how recently a patient was infected with HIV is known as a “recency” test. Researchers who looked at how the global healthcare sector uses these tests said that besides tracking actual infections, the tests may be useful for HIV prevention planning and estimating new cases in larger populations.
The researchers have therefore called for more widespread use of recency tests to monitor the spread and control of HIV.
In general, recency tests or ‘recency assays’ can be used to test for many things. It might be used for following up on how someone might have got infected (contact tracing), or for identifying areas with high infections. But these tests have not been scientifically verified for such purposes.
In this work, researchers reviewed how HIV recency tests are being used globally, as a step towards verifying their use for disease monitoring.
They interviewed people working with the World Health Organisation (WHO) and the United Nations (UN) about the use of recency tests in HIV testing programmes. The WHO and UN are big institutions that oversee health issues around the world.
They also searched for available documents on the topic, published between 2010 and 2021.
They found 90 relevant documents.
Of these, 65 used recency tests to check for new HIV infections. The researchers said that among the 65 studies that had used recency tests to estimate new cases, some did that in large national surveys, while others used them to estimate new cases in large and high risk populations. The researchers said the 65 studies provided strong evidence, because they had shown that the recency tests were very effective.
The researchers said the other 25 studies used the test for general HIV monitoring purposes. Evidence from these studies was generally weak because those studies only reported on what was done, but did not validate findings related to effectiveness of recency tests when used for these purposes.
The researchers further said, out of the 25 studies, 16 (64%) used what they got from recency tests to estimate new HIV infections in the larger general population. While the other 9 used recency test results for other analysis, for example, to do molecular genetic analyses. In molecular genetic analysis, scientists used genetic molecules like DNA to study differences that could put some individuals at more risk than others.
The researchers said they found 2 studies that used genetic information to study how different sexual behaviours affected spread of HIV.
They also said among those 25, they found some researchers who used recency tests to report on new HIV cases in routine HIV programmes, and others who informed targeted prevention planning in another long-term study.
Finally, the researchers said the use of recency tests for other purposes might increase now that the government of the United States of America had started a programme that funds poor countries with HIV, and it required that recency tests be done together with the usual HIV tests.
They cautioned that some of the recency tests they reviewed were no longer used because of their poor performance. The researchers also said some other relevant documents were not included in this review as they were only found after the review had been completed.
This work was done by researchers from South Africa, the USA and Switzerland.
HIV assays designed to detect recent infection, also known as "recency assays,"are often used to estimate HIV incidence in a specific country, region, or subpopulation, alone or as part of recent infection testing algorithms (RITAs). Recently, many countries and organizations have become interested in using recency assays within case surveillance systems and routine HIV testing services, and in measuring other indicators beyond incidence, generally referred to as "non-incidence surveillance use cases."
To identify best methodological and field implementation practices for the use of recency assays to estimate HIV incidence and trends in recent infections for key populations or specific geographic areas, we undertook: 1) a global Call for Information released from WHO/UNAIDS; and 2) a systematic review of the literature to: (a) assess the field performance characteristics of commercially available recency assays, (b) understand the use of recency testing for surveillance in programmatic and laboratory settings, and (c) review methodologies for implementing recency testing for both incidence estimation and non-incidence use cases.
Among the 90 documents ultimately reviewed, 65 (88%) focused on assay/algorithm performance or methodological descriptions, with high-quality evidence of accurate age- and sex- disaggregated HIV incidence estimation at national or regional levels in general population settings, but not at finer geographic levels for prevention prioritization. The remaining 25 documents described field-derived incidence (n=14) and non-incidence (n=11) use cases, including integrating RITAs into routine surveillance and assisting with molecular genetic analyses, but evidence was generally weaker or only reported on what was done, without validation data or findings related to effectiveness of recency assays when used for these purposes.
HIV recency assays have been widely validated for estimating HIV incidence in age- and sex-specific populations at national and sub-national regional levels; however, there was a lack of evidence validating the accuracy and effectiveness of using recency assays for nonincidence surveillance use cases. The evidence identified through this review will be used in forthcoming technical guidance on the use of HIV recency assays for surveillance use cases by WHO and UNAIDS; further evidence on methodologies and effectiveness of non-incidence use cases is needed.
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