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Phys. Ther. Korea 2020; 27(4): 233-240
Published online November 20, 2020
https://doi.org/10.12674/ptk.2020.27.4.233
© Korean Research Society of Physical Therapy
Exploring Concurrent Validity and Item Level Analysis for Two Korean Versions of Health-Related Quality of Life Instrument: EQ-5D vs. WHOQOL-BREF
Bongsam Choi 
, PT, MPH, PhD
Department of Physical Therapy, College of Health and Welfare, Woosong University, Daejeon, Korea
Correspondence to: Bongsam Choi
E-mail: bchoi@wsu.ac.kr
https://orcid.org/0000-0002-0165-4941
Abstract
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Background: Cross-culturally adapted questionnaires may not be comparable to their original version.
Objects: To examine concurrent validity of two health-related quality of life (HRQOL) instruments for the Korean versions of EuroQOL-5 Dimension (EQ-5D) and the abbreviated version of the World Health Organization Quality of Life (WHOQOL-BREF) instrument.
Methods: A total of 139 cancer survivors from two rehabilitation institutes was recruited. All participants were registered for palliative rehabilitation care. Both instruments were concurrently administered by health care providers following the second bout of the rehabilitation cares. Rasch partial credit model and Spearman’s correlation analysis were used to investigate: 1) dimensionality, 2) hierarchical item difficulty, and 3) concurrent validity using correlations between two instruments.
Results: For the WHOQOL-BREF, all items except negative feeling, pain, dependence of medical aid, were found to be acceptable, while all items of EQ-5D were acceptable. There was an evidence of negative correlations between EQ-5D and 4 domains of WHOQOL-BREF. Two correlations were strong (EQ-5D vs. physical health domain, ρ = –0.610, 95% CI = –0.716 to –0.475) and moderate (EQ-5D vs. psychosocial domain, ρ = –0.402, 95% CI = –0.546 to –0.236). Other two correlations were weak (EQ-5D vs. social relationship and environmental domains, ρ = –0.242, 95% CI = –0.401 to –0.075 and ρ = –0.364, 95% CI = –0.514 to –0.207, respectively). Item difficulty calibrations of the two measurements were ranged from –0.84 to 0.86 for the EQ-5D and –1.07 to 1.06 for the WHOQOL-BREF.
Conclusion: The study provides some supports for the concurrent validity of the two Korean versions of HRQOL instrument, with evidences of weak to strong correlations between the EQ- 5D and four domains of the WHOQOL-BREF applied to various cancer survivors. Additionally, the cancer survivors appeared to have more of a tendency to view the EQ-5D items as being slightly more challenging than the WHOQOL-BREF items.
Keywords: Cancer survivors, Palliative care, Patient outcome assessment, Quality of life
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ARTICLE
Phys. Ther. Korea 2020; 27(4): 233-240
Published online November 20, 2020 https://doi.org/10.12674/ptk.2020.27.4.233
Copyright © Korean Research Society of Physical Therapy.
Exploring Concurrent Validity and Item Level Analysis for Two Korean Versions of Health-Related Quality of Life Instrument: EQ-5D vs. WHOQOL-BREF
Bongsam Choi , PT, MPH, PhD
Department of Physical Therapy, College of Health and Welfare, Woosong University, Daejeon, Korea
Correspondence to:Bongsam Choi
E-mail: bchoi@wsu.ac.kr
https://orcid.org/0000-0002-0165-4941
Abstract
Background: Cross-culturally adapted questionnaires may not be comparable to their original version.
Objects: To examine concurrent validity of two health-related quality of life (HRQOL) instruments for the Korean versions of EuroQOL-5 Dimension (EQ-5D) and the abbreviated version of the World Health Organization Quality of Life (WHOQOL-BREF) instrument.
Methods: A total of 139 cancer survivors from two rehabilitation institutes was recruited. All participants were registered for palliative rehabilitation care. Both instruments were concurrently administered by health care providers following the second bout of the rehabilitation cares. Rasch partial credit model and Spearman’s correlation analysis were used to investigate: 1) dimensionality, 2) hierarchical item difficulty, and 3) concurrent validity using correlations between two instruments.
Results: For the WHOQOL-BREF, all items except negative feeling, pain, dependence of medical aid, were found to be acceptable, while all items of EQ-5D were acceptable. There was an evidence of negative correlations between EQ-5D and 4 domains of WHOQOL-BREF. Two correlations were strong (EQ-5D vs. physical health domain, ρ = –0.610, 95% CI = –0.716 to –0.475) and moderate (EQ-5D vs. psychosocial domain, ρ = –0.402, 95% CI = –0.546 to –0.236). Other two correlations were weak (EQ-5D vs. social relationship and environmental domains, ρ = –0.242, 95% CI = –0.401 to –0.075 and ρ = –0.364, 95% CI = –0.514 to –0.207, respectively). Item difficulty calibrations of the two measurements were ranged from –0.84 to 0.86 for the EQ-5D and –1.07 to 1.06 for the WHOQOL-BREF.
Conclusion: The study provides some supports for the concurrent validity of the two Korean versions of HRQOL instrument, with evidences of weak to strong correlations between the EQ- 5D and four domains of the WHOQOL-BREF applied to various cancer survivors. Additionally, the cancer survivors appeared to have more of a tendency to view the EQ-5D items as being slightly more challenging than the WHOQOL-BREF items.
Keywords: Cancer survivors, Palliative care, Patient outcome assessment, Quality of life
Fig 1.
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Table 1 . Fit statistics of the WHOQOL-BREF in descending order of difficulty.
Items Difficulty (logits) Infit MnSq ZSTD Outfit MnSq ZSTD WHOQOL 26 Negative feeling (Psy) 1.06 2.29 8.5 2.59 9.9 WHOQOL 12 Financial support (E) 0.72 1.10 1.0 1.09 0.8 WHOQOL 14 Leisure activity (E) 0.69 1.13 1.2 1.11 1.0 WHOQOL 18 Work capacity (P) 0.64 0.95 –0.5 0.93 –0.6 WHOQOL 3 Pain (P) 0.58 2.88 9.9 3.11 9.9 WHOQOL 10 Energy for daily life, 1.83 (P) 0.50 0.83 –1.6 0.83 –1.6 WHOQOL 11 Bodily image (Psy) 0.40 0.80 –1.9 0.80 –1.9 WHOQOL 5 Positive feeling (Psy) 0.29 0.79 –2.0 0.80 –1.9 WHOQOL 13 Accessibility of information (E) 0.17 0.79 –2.0 0.78 –2.1 WHOQOL 16 Sleep and rest (P) 0.15 1.09 0.8 1.10 0.9 WHOQOL 21 Sexual activity (S) 0.12 0.75 –2.4 0.76 –2.3 WHOQOL 8 Security (E) 0.10 0.63 –3.8 0.63 –3.8 WHOQOL 9 Physical environment (E) –0.01 0.65 –3.6 0.65 –3.5 WHOQOL 15 Mobility (P) –0.04 1.03 0.3 1.02 0.2 WHOQOL 17 Activities of daily living (P) –0.07 0.64 –3.6 0.65 –3.6 WHOQOL 7 Concentration (Psy) –0.13 0.84 –1.5 0.86 –1.3 WHOQOL 19 Self-esteem (Psy) –0.19 0.64 –3.6 0.64 –3.7 WHOQOL 4 Dependence of medical aids (P) –0.41 1.83 6.0 1.98 6.9 WHOQOL 6 Personal belief (Psy) –0.56 0.99 0 1.00 0.1 WHOQOL 22 Social support (S) –0.60 0.76 –2.3 0.77 –2.2 WHOQOL 20 Personal relationship (S) –0.71 0.66 –3.4 0.66 –3.3 WHOQOL 23 Home environment (E) –0.80 0.73 –2.6 0.75 –2.3 WHOQOL 25 Transport (E) –1.00 0.65 –3.4 0.66 –3.3 WHOQOL 24 Health care (E) –1.07 0.77 –2.1 0.76 –2.2 WHOQOL-BREF, abbreviated version of the World Health Organization Quality of Life; MnSq, mean square standardized residuals; ZSTD, Z score standardized; Psy, psychosocial domain; E, environmental domain; P, physical heath domain; S, Social Relationship domain..
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Table 2 . Fit statistics of the EQ-5D in descending order of difficulty.
Items Difficulty (logits) Infit MnSq ZSTD Outfit MnSq ZSTD EQ-5D 5 anxiety/depression 0.86 1.15 1.3 1.13 1.1 EQ-5D 3 usual activities 0.17 0.78 –1.9 0.77 –2.0 EQ-5D 4 pain/discomfort 0.00 0.92 –0.6 0.93 –0.5 EQ-5D 2 self-care1 –0.19 0.94 –0.4 0.90 –0.8 EQ-5D 1 mobility –0.84 1.21 1.7 1.19 1.5 EQ-5D, EuroQOL-5 dimension; MnSq, mean square standardized residuals; ZSTD, Z score standardized..
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Table 3 . Spearman’s correlation coefficients between scores of EQ-5D and 4 domain scores of WHOQOL-BREF.
HRQOL Instruments and Domains WHOQOL- Physical Health WHOQOL- Psychosocial WHOQOL- Social Relationship WHOQOL- Environmental EQ-5D –0.610** (–0.716 to –0.475) –0.402** (–0.546 to –0.236) –0.242** (–0.401 to –0.075) –0.364** (–0.514 to –0.207) WHOQOL-Physical Health 0.580** (0.431 to 0.705) 0.477** (0.326 to 0.616) 0.575** (0.432 to 0.698) WHOQOL-Psychosocial 0.561** (0.417 to 0.671) 0.705** (0.599 to 0.790) WHOQOL-Social Relationship 0.555** (0.432 to 0.674) Values are presented as Spearman's correlation coefficient (95% confidence intervals). EQ-5D, EuroQOL-5 dimension; WHOQOL-BREF, abbreviated version of the World Health Organization Quality of Life. **p < 0.01..