Decreasing Proportion of Recent Infections among Newly Diagnosed HIV-1 Cases in Switzerland, 2008 to 2013 Based on Line-Immunoassay-Based Algorithms

PLoS One. 2015 Jul 31;10(7):e0131828. doi: 10.1371/journal.pone.0131828. eCollection 2015.

Abstract

Background: HIV surveillance requires monitoring of new HIV diagnoses and differentiation of incident and older infections. In 2008, Switzerland implemented a system for monitoring incident HIV infections based on the results of a line immunoassay (Inno-Lia) mandatorily conducted for HIV confirmation and type differentiation (HIV-1, HIV-2) of all newly diagnosed patients. Based on this system, we assessed the proportion of incident HIV infection among newly diagnosed cases in Switzerland during 2008-2013.

Methods and results: Inno-Lia antibody reaction patterns recorded in anonymous HIV notifications to the federal health authority were classified by 10 published algorithms into incident (up to 12 months) or older infections. Utilizing these data, annual incident infection estimates were obtained in two ways, (i) based on the diagnostic performance of the algorithms and utilizing the relationship 'incident = true incident + false incident', (ii) based on the window-periods of the algorithms and utilizing the relationship 'Prevalence = Incidence x Duration'. From 2008-2013, 3'851 HIV notifications were received. Adult HIV-1 infections amounted to 3'809 cases, and 3'636 of them (95.5%) contained Inno-Lia data. Incident infection totals calculated were similar for the performance- and window-based methods, amounting on average to 1'755 (95% confidence interval, 1588-1923) and 1'790 cases (95% CI, 1679-1900), respectively. More than half of these were among men who had sex with men. Both methods showed a continuous decline of annual incident infections 2008-2013, totaling -59.5% and -50.2%, respectively. The decline of incident infections continued even in 2012, when a 15% increase in HIV notifications had been observed. This increase was entirely due to older infections. Overall declines 2008-2013 were of similar extent among the major transmission groups.

Conclusions: Inno-Lia based incident HIV-1 infection surveillance proved useful and reliable. It represents a free, additional public health benefit of the use of this relatively costly test for HIV confirmation and type differentiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Algorithms
  • Cross-Sectional Studies
  • Epidemiological Monitoring*
  • Female
  • HIV Antibodies / blood*
  • HIV Infections / diagnosis
  • HIV Infections / epidemiology*
  • HIV Infections / virology
  • HIV-1 / immunology
  • HIV-2 / immunology
  • Humans
  • Immunoassay / methods
  • Male
  • Switzerland / epidemiology

Substances

  • HIV Antibodies

Grants and funding

This study was financed by contracts 07.005822, 09.001294, 10.001983 and 11.005726 with the Swiss Federal Office of Public Health (SFOPH); see: http://www.bag.admin.ch/org/index.html?lang=en. Even though one of the authors (MDG) is an employee of the SFOPH, the funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Institut Dr. Viollier AG, Clinique de la Source, and Labor Synlab Luzern provided support in the form of salaries for authors DC, CA & MB respectively, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.