Big increases in diagnosis rates of acute HIV infection (AHI) can be achieved with the use of targeted pooled nucleic acid amplification testing (NAAT), research published in AIDS shows. The study was conducted in Vancouver and focused on diagnoses of acute infection among gay and other men who have sex with men (MSM). The rate of AHI diagnoses increased significantly after NAAT was introduced. It was accompanied by social marketing campaigns, which informed gay men about the benefits of this testing technology and the importance of early detection of HIV infection.
“If pooled NAAT had not been in place, 46% of men with AHI would have been given a negative test result,” comment the authors. “We…postulate that two social marking campaigns…contributed to our high diagnostic yield.”
Acute HIV infection is characterised by a high viral load, increasing an individual's infectiousness. Modelling studies suggest that up to 50% of new HIV infections have their source in individuals with acute infection.
However if individuals are diagnosed, behaviour change frequently occurs. Moreover there is the opportunity to offer prevention interventions such as partner notification, behavioural support and early antiretroviral therapy. The identification of people with acute HIV infection is therefore a public health priority.
NAAT is a potential tool to achieve this goal. This form of testing can usually detect infections 7 to 15 days after the infection occurs. This compares to 20 to 30 days for third-generation enzyme immunoassay (EIA) testing. Targeted use of NAAT for communities with a high risk of HIV has been shown to be cost-effective.
Investigators in Vancouver wanted to see if the introduction of NAAT testing increased the detection of acute HIV infection among MSM. They also examined the possible impact of two social marketing campaigns targeted at gay men and focusing on new testing technologies and acute infection.
The study population consisted of men accessing HIV testing at six clinics. These clinics were selected because large numbers of MSM are diagnosed there.
NAAT testing was introduced at these clinics in April 2009. The authors compared the volume of HIV tests and rates of diagnoses at these clinics in the three years before (April 2006 to March 2009) and after (April 2009 to March 2012) the implementation of NAAT testing.
Two social marketing campaigns were implemented during the study period. The first ran between December 2009 and February 2010 and focused on raising awareness of rapid testing and NAAT among gay men. The second ran between June and August 2010 and was targeted at gay men having risky sex or entering new relationships. It was intended to raise awareness of acute infection and the increased risk of transmission at this stage (rather than, for example, describing seroconversion symptoms).
A total of 18,393 HIV tests were performed in the period before NAAT was introduced; 218 patients tested HIV positive, including 19 individuals with acute HIV infection.
There were 21,967 HIV tests post-implementation; 217 individuals with HIV were diagnosed, including 54 with AHI.
The AHI diagnosis rate increased from 1.03 per 1000 men pre-NAAT to 1.84 per 1000 men after NAAT was introduced. This increase was significant (p = 0.003). One third of all acute infections were diagnosed at a single clinic, located in a community gay men's health agency.
The investigators focused on the 54 cases of acute infection identified after the introduction of NAAT. They found that 25 (46%) of these individuals were non-reactive using third-generation EIA testing. Therefore, the addition of pooled NAAT achieved a 11.5% increase in the overall diagnostic yield.
The investigators believe the detection of these additional men was of public health significance. “The early diagnosis of 25 men in our study potentially avoided 25 new cases of HIV among MSM in Vancouver,” suggest the authors.
There was a significant increase in the volume of HIV tests conducted after the introduction of NAAT (p = 0.023). There was evidence of repeat testing, with an increase in the number of prior HIV tests reported (p = 0.002). Diagnosis rates of both acute and non-acute infections increased (p = 0.015).
“Our findings suggest a positive impact of social marketing, which may be related both to the sustained nature of the social marketing, and our emphasis on the nature of AHI and promoting availability of an ‘early test’ soon after a potential exposure,” write investigators.
They conclude, “Our findings confirm the introduction of pooled NAAT in targeted settings with high HIV diagnoses rates is effective at increasing diagnostic yield and suggests that the implementation of AHI social marketing campaigns may promote earlier diagnosis and more frequent HIV testing.”
Gilbert M et al. Targeted screening and social marketing to increase detection of acute HIV in men who have sex with men in Vancouver, British Columbia. AIDS 27: 2649-54, 2013. (Full-text article available here).