Various Repeatability Metrics Found in the Literature
| Parameter | Symbol | Definition | Comment |
| Difference | d | SUV2 – SUV1 | Test–retest difference in units of original data |
| Relative difference | D | 100 × d/[0.5 × (SUV1 + SUV2)] | Test–retest difference expressed as percentage of mean |
| SD of D | DSD | SD of D over all subjects | SD of d would be used if analysis were performed in original units |
| Within-subject coefficient of variation | wCV | DSD/√2 | Reflects repeatability of a single measurement |
| Repeatability coefficient | RC | 1.96 × √2 × wCV | Reflects 95% limits of repeatability for difference between two measurements under assumption that D is normally distributed |
| Mean absolute percentage difference | MAPD | Mean of |D| over all subjects | |D| indicates absolute value of D |