HIV i-Base

Selected words and phrases

CD4 count – number of CD4 cells in a cubic millimetre of blood. CD4 counts results are given as a number that can be anywhere from 0 to over 2000 (rarely).

The range for an HIV-negative person is usually quoted as 430 – 1690. This means 95% of HIV-negative people have a value somewher between 430 and 1690, but a few people have normal levels above or below this. A ‘normal’ CD4 count for an HIV-positive person getting above 500. This is an ideal goal and many people remain well and healthy with CD4 counts that are below this.

Test results are given in medical report in one of three main formats. ie a CD4 count of 350 can be written as:

  • 350 cells/mm3 (cells per cubic millimetre); or
  • 350 cells/μL (cells per microlitre); or
  • 350 Χ 106 cells/L (times 10 to the power of 6, cells per litre)

See: Units of measure.

UK guidelines recommend starting treatment before your CD4 count drops below 350.

US guidelines recommend starting before your CD4 count drops below 500.

There are circumstances where starting treatment at higher CD4 counts are recommended. These include high viral load, during pregnancy, if coinfected with hepatitis B or C or with tuberculosis (TB), in older people (more than 50 years old) and if other health concerns are present (ie heart disease, kidney disease. diabetes etc), or to reduce the risk of transmission to HIV-negative sexual partners.

X-ray – an abbreviation for x-radiation. An X-ray lung scan is a common way to look for evidence of TB infection. X-rays can also diagnose bone fractures.

abstract – in research, a short summary of a study (usually about 350 words)

mucosal lining is the moist, inner lining of some organs and body cavities (such as the nose, mouth, vagina, lungs, and stomach). Glands in the mucosa make mucous, a thick, slippery fluid. A mucosal lining is also called a mucous membrane.

compensatory mutation – this refer to an additional mutation, usually in the context of the fitness of a virus. For example, the mutations that stop a drug form working often stop the virus from reproducing as well. Additional mutations that return the virus to it’s former fitness are called compensatory mutations. They compensate for the reduced viral fitness. See revertant mutation.