HIV infection

Last updated: Monday, 13, December, 2010
Key Information Appropriate Tests
Diagnosis

HIV antibodies/antigen combination assay, with consent and after counselling.

A positive test should be repeated on a further specimen for confirmation.

A negative test does not exclude infection.

Seroconversion usually occurs within 1 month but may be delayed up to 3 months, even following a high risk exposure.

HIV antigen (p24) has only limited sensitivity; HIV-1 RNA (viral load) may be of use during this 'window period'.
Initial assessment FBC; lymphocyte typing (absolute CD4, CD8 counts); syphilis serology; hepatitis B virus testing, hepatitis C virus testing, cytomegalovirus antibodies, toxoplasma antibodies, HIV-1 antigen, HIV RNA (viral load).
Monitoring

FBC; lymphocyte typing - CD4 and CD8 levels indicate degree of immunosuppression.

HIV-1 RNA provides a measure of viral load and is particularly useful in following the response to therapy.

Beta-2-microglobulin is of limited value HIV drug resistance studies.
Criteria for HIV infection Either repeatedly positive tests for HIV antibody supported by a positive confirmatory test or direct identification of HIV by virus isolation.
CDC classification (original)

Group I
  • Acute mononucleosis syndrome
 See under Lymphocytosis

Group II
  • Asymptomatic infection

Group III
  • Persistent generalised lymphadenopathy
 See Lymphadenopathy

Group IV
  • AIDS and 'AIDS related complex'
 See Category C below and AIDS
CDC staging system (1993)
Category A
  • Acute seroconversion illness
  • Asymptomatic patients
  • Progressive generalised lymphadenopathy
 See Lymphadenopathy
Category B

Symptomatic HIV disease
  • Bacillary angiomatosis
 Cat scratch disease antibodies.
  • Vaginal Candidiasis
 Persistent or poorly responsive to therapy. See Candidiasis
  • Oral Candidiasis
 See Candidiasis
  • Cervical dysplasia
 See Cervical lesion
  • Cervical carcinoma in-situ
 See Cervical lesion
  • Constitutional symptoms
  • Fever >38.5ºC
 See Pyrexia of unknown origin
  • Diarrhoea >1 month
  • Oral hairy leukoplakia
  • Herpes zoster infection

On two occasions or involving more than one dermatome.

See Varicella zoster infection
  • Immune thrombocytopenia
 FBC; platelet antibodies. See Thrombocytopenia
  • Pelvic inflammatory disease
  • Peripheral neuropathy
Category C See AIDS for listing of AIDS defining illnesses.
AIDS surveillance case definition Basis for notification of AIDS.

CD4 count <0.2 x 109/L

 This criterion is used by the CDC but has not been adopted in Australasia.

Category C patients

Any patient with HIV infection and an AIDS defining illness is included in the Australasian AIDS surveillance case definition.

See AIDS