In a previous update we described the window periods of different HIV tests in BC. In this update we will focus on pooled nucleic acid amplification testing (pooled NAAT), which can detect HIV an average of 10-12 days after infection.
This technology combines samples from HIV antibody-negative specimens into pools which are then tested for the presence of the HIV virus. If positive, the pools are broken down to isolate the positive sample.
Since 2009, the BCCDC and the BC Public Health Reference Microbiology Laboratory have conducted a pilot study where pooled NAAT is used for HIV tests ordered from six clinics serving gay, bisexual and other men who have sex with men (MSM) in Vancouver. At the same time, community social marketing campaigns aimed to increase awareness of acute HIV and the importance of testing early after a potential exposure or starting a new relationship.
The findings from this study have now been published in the journal AIDS, with the key findings summarized below.(1)
Summary of evidence
All HIV antibody negative blood specimens from males over 18 years from the six clinics were entered into the pooled NAAT testing algorithm from April 2009 to March 2012. This was accompanied by two social marketing campaigns developed by the Health Initiative for Men (a community-based gay men’s health organization; see example image below).
We used provincial surveillance and testing data to compare the three years before and after the implementation of pooled NAAT.
Introducing pooled NAAT resulted in an increased rate of diagnosis of acute HIV, with 25 men being diagnosed who would otherwise have received a negative test result if pooled NAAT hadn’t been in place. This meant pooled NAAT led to an 11.5% increase in new diagnoses, which is higher than in other studies and thought to be due to the community-based social marketing campaigns.
Supporting evidence for the impact of the campaigns included a gradual increase in the frequency of HIV testing among MSM at the six study clinics, and a shift to earlier diagnosis of HIV seen among MSM newly diagnosed with HIV.
Implications for practice
Implementing pooled NAAT led to an increased capacity for detecting acute HIV at these six clinic sites. As individuals with acute HIV infection have high viral loads and risk of transmission to others, diagnosis in the acute stage (as typically accompanied by behaviour change) can help prevent new HIV infections. This is particularly critical for MSM, who in BC in 2012 comprised 63% of all new HIV diagnosis in the province.
The findings also suggest an important role for community-based social marketing campaigns to promote awareness and uptake of new HIV testing technologies.
On the basis of this study, the BC Public Health Reference Microbiology Laboratory has committed to continuing pooled NAAT at these six clinics, and to see how pooled NAAT can be rolled out to other testing sites in BC.
- Mark Gilbert, Darrel Cook, Malcolm Steinberg, Michael Kwag, Wayne Robert, Glenn Doupe, Mel Krajden, Michael Rekart. Targeting screening and social marketing to increase detection of acute HIV infection in men who have sex with men in Vancouver, British Columbia. AIDS, October 23, 2013: 27(16): 2649-2654. http://journals.lww.com/aidsonline/Abstract/2013/10230/Targeting_screening_and_social_marketing_to.16.aspx
- SmartSexResource STI Updates: Understanding the window periods of HIV tests
For more information
For more information about and findings from the CIHR Team in the Study of Acute HIV Infection in Gay Men, please visit the study website: http://acutehivstudy.com
Dr. Mel Krajden, Associate Medical Director, BC Public Health Microbiology and Reference Laboratory
Darrel Cook, Clinical Prevention Services, BCCDC
Michael Kwag, Clinical Prevention Services, BCCDC