Discordant hepatitis C serological testing in Australia and the implications for organ transplant programs.

Background: Discordant and equivocal hepatitis C (HCV) serology testing is problematic for making decisions regarding deceased organ donor (DOD) transplant allocation based on allograft infection status.

Objectives: This study aimed to analyse the prevalence and follow-up testing of discordant HCV tested patients from an Australian population at increased risk of HCV infection, with prevalence modelling for the Australian DOD population.

Study Design: De-identified patient discordant HCV serology results (primary chemiluminescent microparticle immunoassay and secondary Bio-Rad MonoLisa HCV Ag/Ab Ultra assay) were retrospectively identified in a general referral laboratory between May 2008 and August 2011. Prior and follow-up serology testing was reviewed. Discordant result prevalencewas calculated using Bayes' theorem for the DOD population using Australian DOD rates and HCV seroprevalence.

Results: The tested population had a 6.6% HCV seroprevalence. The rate of discordant serotesting was 0.54%, with no cases identified as having definite HCV infection at follow-up. Two patients had evidence of definite HCV seropositivity before the index discordant test. Modelling for the Australian DOD population of 337 per year estimated a discordant test prevalence of 1.8 per year.

Conclusions: Discordant HCV serotesting may occur for 1 of 185 patients tested in higher risk populations. The majority of such tests represent falsely reactive tests although a small number may reflect partial seroreversion. Amongst Australian DOD, this represents 1 or 2 discordant cases per year. It is likely that if this discordant sample were from a donor with no blood borne virus risk factors, and was concurrently RNA negative, that HCV infectious risk would be extremely low.