9.3.5. Quantitation controls
A number of controls are required for quantifying the amount of virus in a sample. These can be broadly divided into “external reference standards”, which are used to quantify the absolute amount of target in each reaction, and “internal reference standards”, which are used to correct the quantitative data for unique differences between individual samples. The BEEBOOK paper on molecular methods (Evans et al., 2013) describes in detail the function, preparation and application of these standards.