Perceptions of individuals living with spinal cord injury toward preference-based quality of life instruments: a qualitative exploration

Table 1 Key properties of the six preference-based HRQoL instruments discussed by focus group participants ^a

Instrument	Dimensions/domains within the descriptive system	Number of items used to derive a health state valuation	Number of unique health states^b
15D [10]	15: mobility, vision, hearing, breathing, sleeping, eating, speech, elimination, usual activities, mental function, discomfort and symptoms, depression, distress, vitality, sexual activity	15 questions, each with 5 levels of response	More than 30 billion
AQoL-8D [11]	8: independent living, senses, pain, mental health, happiness, self worth, coping, relationships	35 questions, with between 4 and 6 levels of response	More than 60 trillion
EQ-5D-5L [12]	5: mobility, self-care, usual activities, pain/discomfort, anxiety/depression	5 questions, each with 5 levels of response	3125
HUI [13]	6: sensation, mobility, emotion, cognition, self-care, pain	15 questions, with between 4 and 6 levels of response^c	8,000
QWB-SA [14]	5: acute and/or chronic symptoms, self-care, mobility, physical functioning, performance of usual activity	At least 71 questions, with varying response formats^d	1,215
SF-6D (SF-36v2) [15]	6: physical functioning, role limitations, social functioning, pain, mental health, vitality	11 (of 36) questions, with between 3 and 6 levels of response^e	18,000

^aAll preference-based HRQoL measures provide scores that are interpretable on a 0–1 scale, where 0 = health state equivalent to death and 1 = full health. Discussion sequences were as follows: HUI, EQ-5D-5L, 15D, AQoL-8D, QWB-SA, SF-36v2 (focus group 1); 15D, AQoL-8D, QWB-SA, SF-36v2, HUI, EQ-5D-5L (focus group 2); QWB-SA, SF-36v2, HUI, EQ-5D-5L, 15D, AQoL-8D (focus group 3).
^b‘Number of unique health states’ refers to the total number of different ways to complete the instrument. For example, for the EQ-5D-5L there are 5⁵ possible response combinations (5x5x5x5x5 = 3125).
^cAlthough there are 15 items contained in the descriptive system of the Health Utilities Index, scoring algorithms for the HUI Mark 2 (HUI2) and HUI Mark 3 (HUI3) are based on different subsets of these items (12 items and 13 items, respectively).
^dDirect communication with the instrument developers.
^eThe SF-6D can be derived from both the 12-item (SF-12) and 36-item (SF-36) Short Form health surveys; the respective descriptive systems comprise 7 of 12 items and 11 of 36 items. The SF-6D is validated only when derived from the larger 12-item or 36-item Short Form health surveys. It is not appropriate to administer only those items that are used in the derivation of SF-6D utility scores and, therefore, participants were asked to consider the SF-36v2 in its entirety.