Table 3.

Quality-of-life (QOL) measures used in the included studies

Quality-of-life measurement [reference]	Number of items	Instrument description	Scoring system	Studies which used measure in this review
Global quality-of-life measure
Index of Well-Being [54]	9	A validated measure of well-being. Comprises 8 specific items about the individual’s perception of their life. The final item measures their overall satisfaction with life. Each item is rated on a 7-point rating system with a positive aspect on one end and a negative aspect at the other end	The first 8 items have a mean weighted at 1.0 which is added to the score for the last item weighted at 1.1. The total possible scores range from 2.1 (lowest life satisfaction) to 14.7 (highest life satisfaction)	[33]
Short-version of The World Health Organization QoL assessment (WHOQOL-BREF) [55]	26	The WHOQOL-BREF is a shortened version of the WHOQOL-100 which provides a detailed assessment of QOL but may be too lengthy for practical use. 24 items derived from the WHOQOL-100 are used to assess four domains including an individuals’ perception of their physical health (7 items), psychological health (4 items), social relationships (3 items), and their environment (8 items). Two additional questions assess the overall QOL and general health	The items are used to derive a mean score for their respective domain. The additional items are rated on a 5-point Likert scale (1- least score to 5-highest score). The mean score for each domain is transformed in two stages. First, the mean score is multiplied by 4 to derive a score ranging from 4 to 20 which is comparable with the WHOQOL-100 score. Second, the domain scores are converted to a 0-100 scale with higher scores implying better QOL	[41]
Multidimensional Index of Life Quality (MILQ) [56]	35	The MILQ is a validated, patient self-reported instrument that assesses 9 domains, namely, physical, cognitive, and social functioning; physical and mental health; productivity, financial status, intimacy, and relationship with health professionals	Each item is scored on a 7-point Likert scale from 1 (very dissatisfied) to 7 (very satisfied). All subscores of the MILQ are scored with a range from 4 to 28. The composite score ranges from 8 to 24, and is derived as a weighted sum of an individuals’ global QOL	[35]
Health-related quality-of-life measure
The 36-item Medical Outcomes Study Questionnaire (SF-36) [57]	36	A standardized measure of generic health-related QOL with close-ended structured questions. There are 8 dimensions, 4 of which comprise the Physical Component Score (PCS) including measures of limitation in physical functioning, physical health problems with resultant role limitations, bodily pain, and general health perceptions. The other 4 dimensions which comprise the Mental Component Score (MCS) include vitality, social functioning, emotional problems with resultant role limitations, and general mental health	Each respective dimension transformed into 0–100 scale. Higher scores indicate better QOL	[33, 34, 36, 40]
The 12-item Short Form of the Medical Outcomes Study Questionnaire (SF-12) [58]	12	Valid measure which assesses two dimensions of QOL: physical health component (measures of general health, pain assessment, fatigue, physical functioning, and interference of role performance due to physical health limitations), and a mental health component (measures of emotional well-being, vitality, social functioning, and role interference due to emotional health limitations)	Items are measured on different scales including ‘yes’/’no,’ ‘not at all’/‘very much.’ A mean score is generated for each component ranging from 0 to 100. The subscales are normed on the general adult US population with a mean (SD) of 50 (10). Higher scores indicates better HRQOL	[27–30]
RAND 36-item health survey [59]	36	The items in the RAND Health survey were adapted from the 36-item Medical Outcomes Study Questionnaire (SF-36), although having a simpler scoring system. Eight domains are assessed, namely, bodily pain (2 items), energy/fatigue (4 items), physical functioning (10 items), role limitations from physical health problems (4 items), emotional well-being (5 items), role limitations due to emotional problems (3 items), social functioning (2 items), and general health perceptions (5 items). A single item measures perceived change in health	Each item is scored from 0 to 100 (higher scores indicate more favorable health). The items in each domain are averaged to create 8-scale scores	[39]
Disease-specific quality-of-life measure
Minnesota Living with Heart Failure Questionnaire (MLHF) [60]	21	A validated Likert-type instrument created for assessing health-related QOL among patients diagnosed with heart failure. Measures the effect of heart failure on physical and emotional dimensions of life. The physical items include symptoms such as fatigue, swelling, shortness of breath, role functioning with difficulty performing work or social activities. The emotional items assess worry, depression, and losing self-control	Each item is rated from 0 (did not) to 5 (very much prevented me from living as I wanted). Higher scores on the physical and emotional subscales imply lower quality of life	[33, 37]
Quality of Life after Acute Myocardial Infarction (QLMI) [61]	25	Validated and reliable disease-specific instrument which consists of two subscales: The Limitations (QOL Lim) subscale which assesses the frequency of physical symptoms and how much it interferes with daily life, and the Emotional subscale (QOL Em) which assesses patients’ self-esteem, emotional well-being, and ability to manage their illness	The scores range from 1 (all of the time) to 7 (none of the time) with a mean response to all 25 items. Higher scores indicate better QOL	[31, 32]
Kansas City Cardiomyopathy Questionnaire (KCCQ)-QOL subscale [62]	3	The QOL subscale of the self-reported KCCQ is a validated measure which assesses how heart failure impacts patient’s overall QOL. Two items address QOL, while the third item assesses depression	Scored from 0 to 100 with a higher score indicating better QOL	[38]