Assessment of extent of disablement
15. For the purposes of paragraph 1(b) of Schedule 8 (disabilities to be taken into account in assessing the extent of the claimant's disablement) and of regulation 11 of the Benefit Regulations (which further defines the principles of assessment of disablement), an injury or disease other than the relevant disease shall be treated as having been received or contracted before the relevant disease if it was received or contracted on or before the date of onset, and as having been received or contracted after the relevant disease if it was received or contracted after that date.