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HIV — CD4 Thresholds & OI Recognition

CD4 staging, OI risk & recognition clues

Field: Infectious DiseasesCode: ID-04AUpdated: June 2026Reference: ASHM / CDC-NIH Adult OI Guidelines
Opportunistic infection (OI) risk rises sharply once CD4 falls below 200 cells/mm³. Starting and maintaining ART is the best prevention — suppression restores CD4 and reduces OI risk. Test for HIV in anyone presenting with an unexplained or unusual infection.

CD4 thresholds & OI risk

Risk rises sharply once CD4 falls below 200.

>500
Normal range. OI risk very low. Routine GP follow-up; annual VL if stable on ART.
350–500
Mild immunosuppression. Monitor; ensure ART adherence; no specific prophylaxis required.
200–350
Begin watching closely. Vaccinate; screen for latent TB; review adherence at each visit.
100–200
PCP, TB & cryptococcus risk rise — start co-trimoxazole prophylaxis; specialist input.
<100
Severe immunosuppression. MAC, CMV & toxoplasma risk. All indicated prophylaxis; urgent review.

Key OIs — recognition clues

  • PCP (CD4 <200): subacute SOB, dry cough, fever, desaturation on exertion.
  • Toxoplasmosis (CD4 <100): headache, focal neurology, ring-enhancing CNS lesions on imaging.
  • Cryptococcal meningitis (CD4 <100): headache, fever, neck stiffness, raised ICP.
  • CMV retinitis (CD4 <50): floaters, visual loss — urgent ophthalmology review.
  • MAC (CD4 <50): fever, night sweats, diarrhoea, raised LFTs, pancytopenia.
  • Oesophageal candida (CD4 <100): dysphagia, odynophagia; oral thrush usually present.

Safety

  • A first presentation of an OI can be the first sign of undiagnosed HIV — test broadly in unexplained or unusual infections.
  • Interpret CD4 alongside viral load; a falling CD4 with detectable VL suggests adherence failure or resistance — needs specialist input.

Red flags / refer

  • Any suspected opportunistic infection in a person with HIV and low CD4 — refer same day.
  • New neurological signs: headache, focal deficit, confusion, fever.
  • Visual changes (floaters, vision loss) or severe/subacute dyspnoea with desaturation.

ID-04A v1.0 · Reviewed Jun 2026 · Review Jun 2027

Companion sheet: ID-04B (OI prophylaxis, TB co-infection & vaccination). See also ID-01/02 (diagnosis & ART) and ID-03 (STI screening). Verify against ASHM/hiv.guidelines.org.au and the CDC/NIH Adult OI Guidelines before prescribing prophylaxis.