PEP Guidelines

Laboratory Assessment and Follow-up

After potential exposure to HIV, individuals should have baseline and follow-up testing for HIV and other infections (depending on mode of exposure). Table 4 sets out the recommended schedule of testing for individuals who are prescribed PEP.

Table 4: Laboratory evaluation of individuals who are prescribed PEP

TestBaseline (Week 0)Week 2Week 6AWeek 12
HIV serology
(HIV Ab/Ag)		XXX
Hepatitis B serology
(HBsAg, Anti-HBs and Anti-HBc)B		XX
Hepatitis C serology
(HCV Ab)C		XX
STI screenDXXX
Syphilis serologyXXX
UECXEX
Pregnancy testFXX

Legend

A. HIV testing is best performed at week 6, which is 2 weeks after cessation of PEP. However, where a patient is directly transitioning onto PrEP, perform HIV testing at the end of the PEP course at week 4.
Patients who are not prescribed PEP do not need further HIV testing beyond week 6.53
B. HBV surface antigen; HBV surface antibody; HBV core antibody.
PEP can be safely commenced in people with HBV (HBsAg positive). Seek specialist consultation in regard to safely ceasing PEP in those with HBV https://ashm.org.au/initiatives/b-referred/
Individuals with evidence of prior immunity to HBV (Anti-HBs >10 mIU/mL) will require no further follow-up. Non-immune individuals (Anti-HBs <10 mIU/mL) should be offered immunisation and follow-up to 6 months
C. Where HCV Ab positive, and reflex HCV PCR testing is not available, recall patient for HCV PCR testin g. Patientspotentially at risk of HCV acquisition require baseline and follow-up testing for HCV.
D. Only required for sexual exposures. Conduct a full STI screen from all relevant sites as per Hx
E. Seek specialist input for recommendation of alternative PEP drugs if eGFR<60
F. If clinically indicated. Consider emergency contraception

Follow-up of indeterminate HIV test results54,55

Although uncommon, indeterminate HIV test results may occur. This situation is complex and requires the input of a laboratory with expertise in HIV testing and may require additional or different tests.

When a baseline HIV Ag/Ab result is positive and confirmatory testing is delayed, or indeterminate, the clinician should recall the individual and:

  • 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 diarrhoea)57
  • add the recommended third PEP drug to two-drug PEP regimens to minimise the risk of developing antiretroviral resistance
  • continue three-drug PEP regimens
  • seek immediate advice from, or refer to, an HIV specialist and/or discuss with the virologist or microbiologist at the testing laboratory
  • advise the individual that they have a reactive initial test that still requires confirmation
  • advise the individual that 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.
    refer to or provide psychological support

Commencing antiretroviral therapy early during acute HIV infection has been found to delay the development of both positive HIV antibodies and HIV WB tests.58 Therefore, a 28-day course of PEP also has the potential to delay seroconversion. In such situations, it is recommended to follow the advice of a specialist laboratory with regard to tests required to confirm a diagnosis of acute HIV.

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