Source National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Sydney, New South Wales. Rdeacon@nchecr.unsw.edu.au
Understanding patterns of newly acquired hepatitis C virus (HCV) infection is fundamental to assessing the impact of prevention and treatment interventions. However, identifying newly acquired cases is difficult, usually requiring documented testing before and after exposure. As the proportion of cases identified as newly acquired by current New South Wales surveillance methodologies is significantly lower than that identified nationally, the impact on the identification of newly acquired cases of systematic reporting of past negative HCV test results from notifying laboratories was assessed. HCV notifications data for 2007 from two New South Wales laboratories were analysed. Cases with a negative HCV antibody test within the past 24 months were classified as newly acquired.
These were linked to the NSW Department of Health (NSW Health)-identified cases to assess the effectiveness of accessing laboratory data. The laboratories accounted for approximately half of all new HCV notifications in 2007. Of the 2,206 newly diagnosed cases, 21 (1.0%) were newly acquired, 18 of which had not been identified under the current surveillance system, increasing the total number of newly acquired cases to 83 from 65. This increased the yield by 28% and increased the proportion of newly acquired cases from 65/4,192 (1.6%) to 83/4,196 (2.0%). Laboratory-identified cases were significantly more likely than NSW Health-identified cases to be aged 30 years or over. Combined with current reporting mechanisms, laboratory data on previous HCV test results have the potential to increase the number of newly acquired cases identified through the New South Wales surveillance system and to enhance the identification of cases among those aged 30 years or more.