The percentage degree of WPI is drawn from Impairment Tables in Division 1 of the DRCA PI Guide. Only figures specified in the relevant tables can be used. See Chapter 5 for information on calculation using the DRCA PI Guide.    

In cases where the DRCA PI Guide cannot be used, the percentage degree of WPI may be determined by reference to the American Medical Association (AMA) Guides. See Chapter 5.5 for more information.    

Only values specified in the DRCA PI Guide can be used for determining the amount of compensation to be paid. Generally this means that amounts are multiples of 5 and, with the exception of hearing loss under Table 7.1, are whole integers. If a WPI for a hearing loss needs to be combined to determine a combined WPI rating (CWPI), R&C ISH will convert the WPI for the hearing loss to a whole integer prior to the calculation of the CWPI.

Note however that since the Canute decision multiple conditions should be assessed individually as to whether they meet the Act's definition of an injury, and since the Fellowes and Robson decisions impairment from each injury must be assessed separately and compensated independently even where they result in the same functional loss. The decisions highlight the need to give careful consideration on the basis of the medical evidence, as to whether each condition is a distinct and separate injury/disease (as defined in the DRCA).  Impairment arising from each injury must individually meet the appropriate threshold for permanent impairment compensation to be payable for that injury.