Key recommendations
- After potential exposure to HIV, people should have baseline and follow-up testing for HIV, STIs and other BBVs as outlined in Table 4.
- Where HIV testing results are indeterminate, repeat HIV testing should occur one to two weeks later.
- When baseline HIV Ag/Ab result is positive and the HIV WB result is delayed, negative or indeterminate:
- assess for HIV seroconversion symptoms
- seek immediate advice from or referral to an HIV specialist
- add one recommended third drug to two-drug PEP regimen or continue three-drug PEP regimen
- provide or refer for psychological support.
- Advise patient they may be at risk of transmitting HIV and provide advice on actions that can be taken to reduce the risk of onward transmission.
- If two-week HIV Ag/Ab result remains positive or the HIV WB result is delayed, negative or indeterminate follow advice of HIV specialist or specialist laboratory who may recommend testing for HIV pro-viral DNA, which is not Medicare subsidised nor widely available.
- After potential exposure to HIV, people should have baseline and follow-up testing for HIV, STIs and other BBVs as outlined in Table 4.
- Where HIV testing results are indeterminate, repeat HIV testing should occur one to two weeks later.
- When baseline HIV Ag/Ab result is positive and the HIV WB result is delayed, negative or indeterminate:
- assess for HIV seroconversion symptoms
- seek immediate advice from or referral to an HIV specialist
- add one recommended third drug to two-drug PEP regimen or continue three-drug PEP regimen
- provide or refer for psychological support.
- Advise patient they may be at risk of transmitting HIV and provide advice on actions that can be taken to reduce the risk of onward transmission.
- If two-week HIV Ag/Ab result remains positive or the HIV WB result is delayed, negative or indeterminate follow advice of HIV specialist or specialist laboratory who may recommend testing for HIV pro-viral DNA, which is not Medicare subsidised nor widely available.
After a potential exposure to HIV, people should have baseline and follow-up testing for HIV, STIs and other BBVs.
Table 4 sets out the recommended routine testing schedule for those who are prescribed PEP.
Table 4. Laboratory assessment of people who are prescribed PEP
| Test | Baseline | Week 4-6i | Week 12 |
|---|---|---|---|
| HIV (HIV Ag/Ab test) a | X | X | X |
| Hepatitis B (HBV) (HBsAg, Anti-HBs and Anti-HBc) b,c | X | X |
|
| Hepatitis C Hepatitis C (HCV) antibody ± HCV RNA Qual PCR d | X X | X | X |
| Chlamydia and gonorrhoea e | X | X | X |
| Syphilis serology f | X | X | X |
| EUC (including eGFR) h | X | See h | |
| Pregnancy test g | X | X |
a 4th generation HIV antigen/antibody combination test
b HBsAg –HBV surface antigen; Anti-HBs – HBV surface antibody; Anti-HBc – HBV core antibody
c See section: Management of possible exposure to other conditions: HBV
d HCV RNA Qual PCR – Qualitative HCV RNA polymerase chain reaction (PCR) – reflex testing by laboratories following positive HCV Ab test should occur at baseline only if history of past HCV; consider PCR at 4-6 weeks for all occupational exposures, for medico-legal purposes including sexual assault, or for percutaneous exposures if source HCV status is positive or unknown
e See section: Management of possible exposure to other conditions: STIs
f Chemiluminescent Microparticle Immunoassay (CMIA) or Enzyme Immunoassay (EIA); if reactive, laboratories generally perform reflex confirmatory testing and Rapid Plasma Reagin (Venereal Disease Research Laboratory) (RPR [VDRL]) staging
gAssess for risk of pregnancy, perform BHCG serology and consider emergency contraception
hRepeat EUC if abnormal at baseline and/or clinically indicated; eGFR should ideally be calculated using the Cockcroft Gault method73
i At a week-4 visit, assess for transition directly to HIV PrEP.
Follow-up of indeterminate HIV test results 74,75
Although rare, indeterminate HIV test results may occur. These results most commonly occur when the fourth generation HIV screening test is reported as reactive, and the definitive diagnostic HIV western blot (WB) is negative or indeterminate. This situation is complex and requires the input of a laboratory with expertise in HIV testing and may require additional or different tests.
Circumstances in which this situation may occur include:
- true biological false-positive result on the fourth generation HIV Ag/Ab test
- early and evolving HIV infection.
When a baseline HIV Ag/Ab result is positive and an HIV WB result is delayed, negative or indeterminate, the clinician should undertake the following:
- assess for HIV seroconversion symptoms most commonly (in order of decreasing prevalence): fever, fatigue, myalgia, skin rash, headache, pharyngitis, cervical adenopathy, arthralgia, night sweats, and diarrhoea76
- seek immediate advice from or referral to an HIV specialist to minimise the potential risk of developing antiretroviral resistance if taking two-drug PEP74
- add one of the recommended third PEP drugs to two-drug PEP regimens; or continue three-drug PEP regimens
- refer for or provide psychological support
- advise the patient they may be at risk of transmitting HIV and provide advice on actions that can be taken to reduce the risk of onward transmission including condom use and sterile injecting paraphernalia.
Commencing antiretroviral therapy early during acute HIV infection has been found to delay the development of both positive HIV antibodies and HIV WB tests.77 Therefore, a 28-day course of PEP also has the potential to delay seroconversion. In such situations, it is recommended, first, to repeat the HIV test.
A high HIV VL usually occurs in early HIV infection. Low VL test results (usually below 3000 copies/mL) have been reported among people without HIV infection.78 Low-level HIV viraemia using quantitative HIV VL RNA has also been observed among people exposed to HIV who were taking PEP and did not acquire HIV, which may represent aborted infection rather than a false-positive test.79
If, at two weeks, the HIV Ag/Ab result remains positive, and there is a delay with the HIV WB result, or it is negative or indeterminate, follow the advice of an HIV specialist or HIV specialist laboratory that may recommend testing for HIV pro-viral DNA (Note: this test is not Medicare subsidised nor widely available).
