CD4 count

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 …


ChemSex is a common term used by gay men
 for drug use that includes at least one of these three recreational drugs: meth, meph and G. Methamphetamine (crystal/crystal meth/Tina/meth). Mephedrone (meph/drone). GHB/GBL* (G, Gina). Differences between ChemSex and recreational drugs.

Compassionate use

Compassionate use programmes enable people with life-threatening, long-lasting or seriously disabling illnesses to use drugs that have not yet been authorised. This is usually only for drugs that are near to drug approval, especially for people who would be excluded …

compensatory mutation

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 …

clinical cut-off (CCO)

clinical cut-off (CCO) – a test result that is associated with an impact on clinical care. With resistance tests a lower CCO is the level below which a drug is still sensitive or active. This is often set at a …


codon – the word for the junction on genetic material (DNA or RNA) occupied by three nucleotides (or bases) to form an amino acid. In HIV it is most used when refering to drug resistance. There is an amino acid …

confirmatory test

confirmatory test – a second test to double-check the results of a previous one. For example, if your viral load is usually undetectable and then becomes detectable, you need a second confirmatory test. This is to check that the detectable …


cotrimoxazole is combination two antibiotics (trimethoprim and sulfamethoxazole). Tradenames include Septrin and Bactrim. Abbreviations for this combination include SXT, TMP-SMX, TMP-SMZ or TMP-sulfa. Cotrimoxazole is commonly used in HIV care as a prophylaxis against PCP and toxoplasmosis. Everyone with a …


chorioamnionitis is an inflammation of the membranes that surround the foetus (called the chorion and the amnion). Chorioamnionitis is usually caused by a bacterial infection.


cryoglobulinemia – increased blood levels of abnormal proteins called cryoglobulins that can inflame blood vessels and thicken blood.


cirrhosis – severe scarring of the liver (see fibrosis) that makes it difficult for the liver to carry out its functions


coinfection – having more than one infection, eg HIV and TB, or HIV and hepatitis C.

Cubic millimitre

cubic millimitre (mm3) – a measure of a volume. Same as microlitre (µL) and million parts per litre (106/L). Practically, a drop of blood.


Ctrough – another word for Cmin.


CSF – cerebral spinal fluid – the fluid that circulates around the brain and spinal column.


C-section – Caesarean section, procedure to deliver a baby that involves making a cut through the abdominal wall to surgically remove the infant from the uterus.


cryptococcus (crypto) – a fungal infection. Can cause meningitis.


cross-resistance – when resistance to one drug causes resistance to other similar drugs. This commonly happens for every class or family of HIV drugs: nukes, NNRTIs, PIs, integrase inhibitors, and some entry inhibitors.

Cross-over study

cross-over study – where patients in a study ‘roll-over’ to a second related study. For example, this can be after a fixed period in a study (ie after 48 weeks) or after another event (for example, not having a treatment …


compartment – place in the body that has barriers limiting both HIV and HIV drugs from moving freely. Key sites include the brian, the genital tract and some organs. Also called sanctuary sites.

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