of the above groups in the preceding 10 weeks People who have been newly diagnosed with, or have been treated for, syphilis, gonorrhoea, chlamydia, or genital ulcers in the preceding 10 weeks A child who is 18 months old or younger and born to a mother known to be infected with, or at increased risk for, HIV, HBV or HCV infection A child who has been breastfed within the preceding 6 months, and the mother is known to be infected with, or at increased risk for, HIV, HBV or HCV infection When a deceased potential organ donor’s medical/behavioural history cannot be obtained or risk factors cannot be determined When a deceased potential organ donor’s blood specimen is haemodiluted so that testing for HIV, HBV, and HCV infection is less reliable April 2021 version 1.5 14 If a donor has recently been infected with HIV, HBV or HCV, it is possible that the donor may still be in the eclipse or window period of infection (see Table 2.3) and transmission may still occur despite negative results on serology and NAT. The degree of residual infection risk associated with a specific donor is influenced by the nature of the donor’s risk behaviour(s) and how recently the risk behaviour(s) occurred in relation to the time of donor testing.13 Higher underlying incidence in an at-risk group or longer eclipse/window periods correspond with a higher residual risk of an undetected infection. Table 2.3: Window and eclipse periods* for pathogen testing. Modified from Humar.14 *Window period = the interval from infection to ability to detect that infection by serological testing; elipse period = the interval after infection for which infection cannot be detected by either NAT or serological testing. Table 2.4 lists the estimated risks of undetected HIV, HBV or HCV infection in Australian donors by risk behaviour type, based on Australian epidemiological data.15 The estimates shown are preliminary, with final results expected to be published in 2019. These estimates of residual risk are based upon the best available local evidence, but are limited where the underlying data were sparse – notably in the case of commercial sex workers and high risk partners. Data on the incidence of HBV in Australia are not available, therefore residual risk estimates were derived from estimates of the prevalence of hepatitis B core antibody (HBcAb) and hepatitis B surface antigen (HBsAg) in each risk group. It is also important to note that these residual risk estimates are based on historical data. Improvements in the treatment of HIV, HBV and HCV (especially HCV) and corresponding reductions in incidence, and/or improvements in testing (resulting in shorter eclipse and window periods), would result in lower residual infection risks. The risk of an undetected HIV infection is low in all cases. Donors with the highest residual risk, men who have recently had sex with men, have an estimated 1 in 1621 residual risk of undiagnosed HIV based on a negative enzyme immunoassay (EIA) result alone, and a 1 in 5092 residual risk based on a negative EIA + NAT. For recent intravenous drug users, prisoners, commercial sex workers and increased risk partners, the risk of undiagnosed HIV is less than 1 in 10,000. Risk of undetected HCV is highest among recent IVDU (past 10 weeks), among whom the residual risk of HCV is 1 in 31 based on a negative EIA result alone, and 1 in 299 based on a negative EIA + NAT. The residual risk of HCV is similar among the prison population: 1 in 45 based on EIA alone, and 1 in 344 based on EIA + NAT. The risk of undetected HBcAb (i.e. likely past HBV infection) is highest for recent IVDU: 1 in 103 based on a negative EIA, and 1 in 205 for a negative EIA + NAT. The risk of undetected HBsAg (i.e. active HBV infection) is also highest for recent IVDU: 1 in 1216 based on EIA alone, and 1 in 2430 based on a negative EIA + NAT. It should be noted that the underlying risk behaviours within each risk factor category are not homogenous. The residual risks reported in Table 2.4 represent conservative estimates of the infectious risks associated with donors in each risk category, however the actual risk of undetected infection in a given test-negative donor may be significantly lower depending on their history. For example, residual risks of HCV among IVDU may be lower for IVDU participating in needle exchange programs and receiving opioid substitution, compared to IVDU not participating in these programs.16 For all donors, test results should be interpreted in the context of the donor’s personal history, and the residual risk estimates given in Table 2.4 should be used as a guide but not as a definitive numbers. Pathogen Standard serology Nucleic acid testing HIV 17 – 22 days 5 – 6 days HBV 35 – 44 days 20 – 22 days HCV ~70 days 3 – 5 days April 2021 version 1.5 15 Table 2.4: Residual riska of undiagnosed HIV, HBV or HCV infection for Australian donors at increased risk, by risk factor and testing strategy. Adapted from Waller et al.15 a Residual infection risk is the predicted rate of undetected infection in donors who test negative for HIV, HCV or HBV, depending on risk factor and testing strategy, calculated as RR = 1 – e(-incidence)*(eclipse period or serological window) bIncidence estimates are based on a systematic review and meta-analysis of studies from 2000-2017 reporting original estimates of Australian HIV, HCV or HBV prevalence or incidence. Incidence rates and confidence intervals were