Eurosurveillance - Volume 13, Issue 36, 04 September 2008

Although all the assays for recent infections have shown limitations, they have been already used in many circumstances to estimate either HIV incidence or, at least, the proportion of recent infection in various populations. Even if they cannot be recommended for routine use worldwide because of insufficient data on their performance to provide precise incidence in different populations, a few studies have already illustrated their usefulness.

The Serological Testing Algorithm for Recent HIV Seroconversion (STARHS) is a generic term for several laboratory techniques that can be used to differentiate recent from long standing infections with human immunodeficiency virus-1 (HIV-1). There are several other approaches that identify acute seroconverters, but STARHS methods are distinguished by their ability to identify infections that occurred during an extended period of 4-6 months prior to sampling. While the STARHS techniques have been employed on an individual basis, their main usefulness lies in the potential of estimating the rate of acquisition of new HIV infection, or incidence, in a population by application to cross-sectional sero-surveys. This is substantially simpler and less expensive than cohort studies. As such, STARHS techniques facilitate the timely monitoring of the impact on HIV incidence of factors such as interventions, demographic factors and behavioural patterns. The major STARHS techniques currently available are described. Furthermore, the principles behind the methods used are discussed and the limitations of the current assays and the confounding factors that may affect assay specificity are described. A model algorithm for the application of a STARHS assay is shown. Finally, we outline recommendations for laboratory quality systems that will improve the efficiency of STARHS testing, reproducibility of results and reliability of incidence estimates.

Since the 1990s, the development of laboratory-based methods has allowed to estimate incidence of human immunodeficiency virus (HIV) infections on single samples. The tests aim to differentiate recent from established HIV infection. Incidence estimates are obtained by using the relationship between prevalence, incidence and duration of recent infection. We describe the principle of the methods and typical uses of these tests to characterise recent infection and derive incidence. We discuss the challenges in interpreting estimates and we consider the implications for surveillance systems. Overall, these methods can add remarkable value to surveillance systems based on prevalence surveys as well as HIV case reporting. The assumptions that must be fulfilled to correctly interpret the estimates are mostly similar to those required in prevalence measurement. However, further research on the specific aspect of window period estimation is needed in order to generalise these methods in various population settings.

New systems of surveillance to better monitor the dynamics of HIV are needed. A national surveillance of new HIV diagnoses which included the collection of dried serum spots (DSS) to identify recent infections (<6 months) using an EIA-RI assay was implemented in 2003 in France. The collection of DSS is based on the voluntary participation by both patients and microbiologists. Multivariate analysis was used to identify factors associated with recent infection (RI). Between July 2003 and December 2006, 14,155 cases newly diagnosed for HIV were reported. A minority of patients refused the collection of DSS (3.3%) and the rate of participation of laboratories was 80%. The test was performed for 10,855 newly diagnosed HIV cases, the overall proportion of RI was 23.1% (95% CI, 22.3%-23.9%). The proportion of RI was higher among men who have sex with men (MSM) (42.8%) than among heterosexuals (16.3%). Among heterosexuals, it varied by current nationality: 27% among French versus 8.4% among Africans. The risk of RI was greater for MSM (aOR=1.8), those of French nationality (aOR=3.9), those with high-economic status (aOR=1.2), those tested after a risk exposure (aOR=1.4), those tested for HIV three or more times during their lifetime (aOR=2.5). The risk of RI decreased with age. A nation-wide implementation of RI monitoring is feasible. The information on RI is very useful for renewing prevention messages, particularly among population in which HIV transmission is on going, such as MSM.

Portugal has been the western European country with the highest rate of notified acquired immunodeficiency syndrome (AIDS) cases since 1999 and human immunodeficiency virus (HIV) infection cases since 2000. Nonetheless, exact information on the magnitude and trends of recently acquired infections is missing. In a cross-sectional study we aimed to determine HIV prevalence, the proportion of recently acquired infections and the incidence among patients attending a Sexually Transmitted Infections (STI) clinic and among HIV positive cases tested at the AIDS Reference Laboratory (ARL), by using the Avidity Index (AI) of antibodies to identify recent HIV-1 seroconversions. Demographic and behavioural data were collected. At the STI clinic 253 patients were enrolled, 16 were found to be HIV infected (14 HIV-1, 2 HIV-2) and a prevalence of 6.3% was obtained. Four recent HIV-1 infections were identified and the HIV-1 incidence was 3.3% per year. At the ARL, 332 newly diagnosed cases of HIV-1 infection were studied, 59 (17.8%) were recent infections and an annual incidence of 4.1% was estimated. These findings support STI clinics as key sentinel sites for recently acquired HIV infections and illustrate the viability of testing for recent HIV infections in these settings and reinforce the value of this method in the surveillance for better monitoring current trends of the HIV/AIDS epidemic in Portugal.

Serological methods exist that allow differentiating between recent and long-standing infections in persons infected with HIV. During a pilot study in Berlin between 2005 and 2007 methodologies have been evaluated. In a cross-sectional study blood samples, demographic, laboratory, clinical and behavioural data based on a KABP survey were collected from patients with newly diagnosed HIV infections. The BED-CEIA was used to determine recency of infection. Recent HIV infections contributed 54% (CI [95%]: 45; 64) in MSM and 16% (CI [95%]: 0; 39) in patients with other transmission risks (p=0.041). Proportions of recent infections were significantly higher in MSM ≤30 years (p=0.019). The mean age was 33.9 (median 34 years) in recent compared with 38.6 years (median: 38 years) in long-standing infections (p=0.011). High-risk behaviour indicated through very low condom use in recently HIV infected MSM could be identified. The results of the pilot study support expectations that the modified application of the method may contribute to improving HIV prevention efforts in Germany. On this basis the Robert Koch Institute implemented a countrywide HIV incidence study to complement HIV surveillance in early 2008. The study is funded by the German Ministry of Health. Data on recent HIV infections and current HIV transmission risks are collected. Design, methods and impact are described in detail.

The recent development of serological assays for human immunodeficiency virus (HIV) that are able to distinguish recent from long-standing infection has generated an important tool for HIV surveillance. In the European Union (EU), a number of different serological assays are being used, and there is the danger that that HIV incidence estimates in different countries, or even within a country, may not be comparable.

On 3 August 2008, the United States (US) Centers for Disease Control and Prevention (CDC) in Atlanta released for the first time estimates for HIV incidence based on a STARHS (serological testing algorithm for recent HIV seroconversion).