In resource-poor countries and communities, sometimes medical facilities and testing is unavailable, and it isn’t possible to decide the appropriate time to begin treatment on the basis of test results. The World Health Organization has developed a disease staging system for HIV infection which is not dependent on testing.

WHO disease staging system for HIV Infection and Disease in Adults and Adolescents

Clinical Stage I:

•  Asymptomatic
• Generalized lymphadenopathy

Performance scale 1: asymptomatic, normal activity

Clinical Stage II:

• Weight loss, < 10% of body weight
• Minor mucocutaneous manifestations (seborrheic dermatitis, prurigo, fungal nail infections, recurrent oral ulcerations, angular cheilitis)
• Herpes zoster within the last five years
• Recurrent upper respiratory tract infections (i.e. bacterial sinusitis)

And/or performance scale 2: symptomatic, normal activity

Clinical Stage III:

• Weight loss, > 10% of body weight
• Unexplained chronic diarrhoea > 1 month
• Unexplained prolonged fever (intermittent or constant), > 1 month
• Oral candidiasis (thrush)
• Oral hairy leucoplakia
• Pulmonary tuberculosis
• Severe bacterial infections (i.e. pneumonia, pyomyositis)

And/or performance scale 3: bedridden < 50% of the day during last month

Clinical Stage IV:

• HIV wasting syndromeⁱ
• Pneumocystis carinii pneumonia
• Toxoplasmosis of the brain
• Cryptosporidiosis with diarrhoea > 1 month
• Cryptococcosis, extrapulmonary
• Cytomegalovirus disease of an organ other than liver, spleen or lymph node (e.g. retinitis)
• Herpes simplex virus infection, mucocutaneous (>1 month) or visceral
• Progressive multifocal leucoencephalopathy
• Any disseminated endemic mycosis
• Candidiasis of esophagus, trachea, bronchi
• Atypical mycobacteriosis, disseminated or lungs
• Non-typhoid Salmonella septicemia
• Extrapulmonary tuberculosis
• Lymphoma
• Kaposi's sarcoma
• HIV encephalopathyⁱⁱ

And/or performance scale 4: bedridden > 50% of the day during last month

Footnotes:

1. HIV wasting syndrome: weight loss of > 10% of body weight, plus either unexplained chronic diarrohea (> 1 month) or chronic weakness and unexplained prolonged fever (> 1 month).
2. HIV encephalopathy: clinical findings of disabling cognitive and/or motor dysfunction interfering with activities of daily living, progressing over weeks to months, in the absence of a concurrent illness or condition other than HIV infection which could explain the findings

 From AVERT.org