Some clinical studies still use the pre-1993 Centers for Disease Control and Prevention (CDC) definition of the stages of HIV disease to describe who is eligible to take part in the trial. For this reason, we have retained this summary of these groups, even though they are no longer used for defining disease stages.

Group I

Acute infection or seroconversion illness.

Group II

Asymptomatic HIV infection.

Group III

Persistent generalised lymphadenopathy.

Group IV.1

Within this category, a person may only be diagnosed as having AIDS (as opposed to non-AIDS symptomatic HIV disease) if one or more of the following diseases is definitively diagnosed, but there must be no evidence of other causes of immunosuppression:

• Candida in the oesophagus, trachea, bronchi or lungs.
• Cryptococcus outside the lungs.
• Cryptosporidiosis with diarrhoea lasting for more than one month.
• Cytomegalovirus outside the liver, spleen or lymph nodes.
• Herpes simplex virus causing prolonged skin problems or involving the lungs or oesophagus.
• Kaposi's sarcoma in a person under the age of 60
• Primary brain lymphoma in a person under 60 years old.
• Lymphoid interstitial pneumonia or pulmonary lymphoid hyperplasia affecting a child younger than 13.
• Widespread Mycobacterium avium intracellulare or M. kansasii.
• Pneumocystis pneumonia.
• Progressive multifocal leukoencephalopathy.
• Toxoplasmosis of the brain.

Group IV.2.A

Regardless of whether any other possible causes of immunodeficiency are present, AIDS is diagnosed if one or more of the diseases listed above or below is confirmed:

• Multiple or recurrent bacterial infections in a child younger than 13.
• Widespread coccidiomycosis.
• HIV encephalopathy.
• Widespread histoplasmosis.
• Isosporiasis with diarrhoea lasting longer than one month.
• Kaposi's sarcoma.
• Primary brain lymphoma.
• Other specific non-Hodgkin's lymphoma.
• Any disseminated mycobacterial infection other than tuberculosis.
• Tuberculosis involving at least one site outside the lungs.
• Recurrent Salmonella septicaemia.
• HIV wasting syndrome.

Group IV.2.B

Regardless of whether any other possible causes of immunodeficiency are present, AIDS is diagnosed if one or more of the diseases listed above or below is diagnosed presumptively:

• Candida of the oesophagus.
• Cytomegalovirus retinitis with loss of vision.
• Kaposi's sarcoma.
• Lymphoid interstitial pneumonia or pulmonary lymphoid hyperplasia affecting a child younger than 13.
• Disseminated mycobacterial disease.
• Pneumocystis pneumonia.
• Toxoplasmosis of the brain.

Group IV.3

If laboratory tests are negative for HIV infection, AIDS can only be diagnosed if: all other causes of immunodeficiency listed earlier are ruled out, and the individual has had either Pneumocystis pneumonia or both an infection listed in section I above and a CD4 count less than 400 cells/mm³.