Modular update to NICE manuals EQ-5D-5L value set: Evidence review document

The EQ-5D is a generic health-related quality of life questionnaire, meaning it can be used across a wide range of diseases, conditions and populations, rather than being specific to one illness. It asks people to rate their degree of impairment in 5 areas ('dimensions'): mobility, self-care, usual activities, pain/discomfort and anxiety/depression. There are 2 versions used in adults: the original 3-level version (3L), introduced in 1990, and the newer, more sensitive 5-level version (5L), released in 2009 (Devlin and Brooks 2017). The levels refer to the number of multiple-choice options (indicating the extent of problems) for each dimension. For ease of reading, the terms 'EQ-5D-3L' and '3L' are used interchangeably, and 'EQ-5D-5L' and '5L' are also used interchangeably.

A mathematical model called a 'value set' converts EQ-5D questionnaire responses to a utility value, where 0 represents dead and 1 represents perfect health. A value set is produced by collecting the public's views about the relative importance of the 5 aspects of health-related quality of life measured by the EQ-5D questionnaire (also known as the 'descriptive system'), and what matters most to them, in a 'valuation study'. People's perceptions of health states vary across cultures and are affected by demographic differences, so value sets are country specific.

Utility values are used in economic models to combine estimates of health-related quality of life with length of life. We express this combination as quality-adjusted life years (QALYs). NICE looks at the extra cost of a new treatment compared with the extra QALYs it provides. This gives us the incremental cost‑effectiveness ratio (ICER), which tells us how much it costs to gain 1 extra QALY. ICERs help us judge whether a treatment offers value for money for the NHS.

Through the severity modifier, NICE committees can give extra weight to the health benefits of a treatment when it is used for a particularly severe condition (referred to from here as 'severity weighting'). A treatment qualifies for severity weighting if the condition it treats is expected to cause a large loss in a person's future QALYs, compared with the future QALYs someone in the general population without the condition would be expected to experience. This loss may be measured as either total QALYs lost (absolute shortfall, AS) or a proportion of the QALYs the person would be expected to experience without the condition (proportional shortfall, PS). The treatment is eligible for severity weighting if either the AS or the PS reaches 1 of the cutoffs set by NICE (see table 6.1 of NICE's technology appraisal and highly specialised technologies guidance manual [PMG36]). When this happens, the QALYs gained from that treatment are multiplied by either 1.2 or 1.7, depending on which cutoff has been reached. Increases in AS or PS, or both, can mean a treatment qualifies for higher severity weighting, which would make the treatment more cost effective (that is, it has a lower ICER).