HIV diagnosis and management, including post exposure prophylaxis and seroconversion illness

Last updated: March 2014


Screening antigen/antibody assay

A positive screen using a fourth generation HIV screening assay provides a presumptive diagnosis.

Western Blot

  • A positive Western Blot assay confirms diagnosis.
  • An indeterminate Western Blot assay correlated with the clinical presentation provides a presumptive diagnosis and must be followed up with repeat testing to demonstrate band evolution.

HIV Viral Load

Is not routinely used as a screening test to diagnose HIV.


  • Treatment of HIV infection is best conducted under specialist or GP specialist care
  • Prior to referral a detailed examination and initial investigations should be ordered

Initial clinical assessment

  • Standard full detailed history which should also include
    • Date of last HIV test
    • HIV acquisition and transmission risk behaviour and contacts
    • History of any Tuberculosis risk exposure
    • Vaccination history
    • Mental health assessment
  • Assessment for current symptoms that require separate investigation
  • Examination as clinically indicated
  • Referral for specialist review
    • HIV specialist
    • Psychology and support services as necessary

Initial investigations

  • Bloods for
    • FBC, EUC, LFT, HIV Viral load
    • HIV Genotype
    • T Cells (CD4 subsets)
    • Syphilis
    • Hepatitis A, B, C serology
    • EBV, CMV, HSV, VZV, Toxoplasma
    • HLA B5701
  • STI testing
  • Pap smear if required
  • Mantoux or Quantaferon Gold +/- CXR as needed

Partner notification

Partner Notification is required and should be conducted by a specialist partner notification officer or experienced HIV clinician

The health advisor should provide information on support services.

Follow up

Patients should be seen for follow up to:

  • review test results
  • confirm appointments with specialists
  • assess mental state
  • review contact tracing
  • review health status.

Patients with HIV are encouraged to maintain a relationship with their usual GP and to continue regular STI screening at recommended intervals

HIV post exposure prophylaxis

Non occupational Post Exposure Prophylaxis following a possible exposure to HIV should be managed in accordance with local and national guidelines.

HIV Seroconversion (primary HIV infection)

Discuss all cases of suspected HIV seroconversion with a senior doctor.

Seroconversion is a highly infectious stage and may be the only clinical presentation before AIDS.


Primary HIV infection (PHI) is the clinical syndrome associated with the development of HIV antibodies.

Clinical diagnosis

PHI occurs in 80% of individuals 2 to 4 weeks after HIV infection. Therefore suspect if high-risk exposure within 2 months and if clinical symptoms include any of the following:

  • rash
  • fever
  • sweats
  • sore throat
  • generalised lymphadenopathy
  • myalgia
  • mucocutaneous ulceration
  • diarrhoea.

Rarer presentations include aseptic meningitis, weight loss or an AIDS-defining infection such as PJP.

Laboratory diagnosis

Serological HIV antibody test 4th generation or combo test (HIV Ab with page 24 Ag)

If initial test negative & you suspect PHI it is essential to bring back in 7 days for a repeat test.

Note: a second negative HIV test at one week confidently excludes that particular clinical presentation as a seroconversion illness, a 3 month window period test is still needed to exclude asymptomatic seroconversion.

Differential diagnosis

Secondary syphilis, other acute viral infections (EBV/ CMV/ HSV)


Patients may rarely require admission for symptom control, discuss with a senior doctor.

Some symptoms associated with seroconversion may need HIV treatment.


Abstain from all sex until results are known (consider highly infections).

Further information

For further information on HIV diagnosis and management including post exposure prophylaxis contact Adelaide Sexual Health Centre.


These guidelines are based on review of current literature, current recommendations of the United States Centers for Disease Control and Prevention, World Health Organization, the British Association for Sexual Health and HIV and local expert opinion.

They are written primarily for use by Adelaide Sexual Health Centre staff and some flexibility is required in applying them to certain private practice situations.