Glossary

standard deviation (SD) – the standard deviation from a mean average, is a measure of the degree of variation from the mean.

RNA – an abbreviation for the scientific word for genetic material found in some types of viruses. It is the abbreviation for ribonucleic acid. It is very similar to DNA but is single-strand rather than the double-strand in DNA. See DNA.

monotherapy – using only one drug.

revertant mutation – this term is used in two ways.

Firstly when referring to a genetic change that shows the virus is returning from a drug resistant mutation back to a wild-type genotype. This can sometimes take several stages. For example, T215E/D/E and S are revertant mutations that can indicate the drug resistant mutation T215Y is being replaced by wild-type (i.e. T215T).

It can also refer to the fitness of a virus. A revertant mutation can refer to an additional mutation that allows the virus to regain viral fitness (most drug mutations also make the vurs less fit). The second example is called a compensatory mutation as is compensates for the reduced fitness caused by the first mutation.

fixed dose combination (FDC) – several drugs combined in one tablet at a standard dose.