Phys. Ther. Korea 2023; 30(1): 32-40
Published online February 20, 2023
https://doi.org/10.12674/ptk.2023.30.1.32
© Korean Research Society of Physical Therapy
Bongsam Choi1 , PT, MPH, PhD, Heesu Kim2
, PT, BS, Sunhwi Bang3
, KMD, Byunggwan Kim4
, PT, Jaekwang Shim5
, PT, PhD
1Department of Physical Therapy, College of Health and Welfare, Woosong University, 2Department of Rehabilitation, The Graduate School of Health and Welfare, Woosong University, Daejeon, 3Hwirim Korean Medicine Hospital, Busan, 4Rehabilitation Center, Bomunsan Ecologic Nursing Hospital, 5Rehabilitation Center, Teunteun Convalescent Hospital, Daejeon, Korea
Correspondence to: Heesu Kim
E-mail: heesukimpt@gmail.com
https://orcid.org/0000-0002-1684-5636
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Equating is a statistical procedure used to create a common measurement scale across two instruments. Item-level information should be taken into consideration so that scores can communicate interchangeably across the instruments. Objects: To investigate a common measurement scale across two health-related quality of life questionnaires (HRQOL) applied to various cancer survivors who underwent palliative care in healthcare institutions.
Methods: A total of 139 cancer survivors who underwent palliative care were recruited from two rehabilitation hospitals and an oriental medicine hospital. Participants consisted of various cancer survivors who presented to the sites for palliative care. They were asked to fill out Korean versions of the World Health Organization Quality of Life (WHOQOL-BREF) and EuroQOL-5 dimension (EQ-5D) questionnaires following the palliative care. For the item level comparison, the Rasch rating scale model was used to investigate how participants regarded individual test items of two instruments in relation to item difficulty calibrations.
Results: All items except the three items fit the Rasch model. One item (anxiety/depression) of the EQ-5D and two items (dependence on medical aids and negative feelings) of the WHOQOL- BREF are misfit. The WHOQOL-BREF targets the survivors well, while the EQ-5D is able to target the survivors with lower HRQOL levels with some ceiling effects. By inspecting the item difficulty calibrations of the two instruments, five items of the WHOQOL-BREF are selected as common items in relation to the EQ-5D. These five items are considered compatible with each other. Differential item functioning (DIF) analysis reveals that the healthcare item of the WHOQOL-BREF vs the self-care item of the EQ-5D exhibits significant DIF.
Conclusion: Findings suggest that one paired item should be taken into consideration when equating the WHOQOL-BREF and the EQ-5D applied to cancer survivors who underwent palliative care.
Keywords: Cancer survivors, Outcome assessment, Palliative care, Psychometrics, Quality of life
Phys. Ther. Korea 2023; 30(1): 32-40
Published online February 20, 2023 https://doi.org/10.12674/ptk.2023.30.1.32
Copyright © Korean Research Society of Physical Therapy.
Bongsam Choi1 , PT, MPH, PhD, Heesu Kim2
, PT, BS, Sunhwi Bang3
, KMD, Byunggwan Kim4
, PT, Jaekwang Shim5
, PT, PhD
1Department of Physical Therapy, College of Health and Welfare, Woosong University, 2Department of Rehabilitation, The Graduate School of Health and Welfare, Woosong University, Daejeon, 3Hwirim Korean Medicine Hospital, Busan, 4Rehabilitation Center, Bomunsan Ecologic Nursing Hospital, 5Rehabilitation Center, Teunteun Convalescent Hospital, Daejeon, Korea
Correspondence to:Heesu Kim
E-mail: heesukimpt@gmail.com
https://orcid.org/0000-0002-1684-5636
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Equating is a statistical procedure used to create a common measurement scale across two instruments. Item-level information should be taken into consideration so that scores can communicate interchangeably across the instruments. Objects: To investigate a common measurement scale across two health-related quality of life questionnaires (HRQOL) applied to various cancer survivors who underwent palliative care in healthcare institutions.
Methods: A total of 139 cancer survivors who underwent palliative care were recruited from two rehabilitation hospitals and an oriental medicine hospital. Participants consisted of various cancer survivors who presented to the sites for palliative care. They were asked to fill out Korean versions of the World Health Organization Quality of Life (WHOQOL-BREF) and EuroQOL-5 dimension (EQ-5D) questionnaires following the palliative care. For the item level comparison, the Rasch rating scale model was used to investigate how participants regarded individual test items of two instruments in relation to item difficulty calibrations.
Results: All items except the three items fit the Rasch model. One item (anxiety/depression) of the EQ-5D and two items (dependence on medical aids and negative feelings) of the WHOQOL- BREF are misfit. The WHOQOL-BREF targets the survivors well, while the EQ-5D is able to target the survivors with lower HRQOL levels with some ceiling effects. By inspecting the item difficulty calibrations of the two instruments, five items of the WHOQOL-BREF are selected as common items in relation to the EQ-5D. These five items are considered compatible with each other. Differential item functioning (DIF) analysis reveals that the healthcare item of the WHOQOL-BREF vs the self-care item of the EQ-5D exhibits significant DIF.
Conclusion: Findings suggest that one paired item should be taken into consideration when equating the WHOQOL-BREF and the EQ-5D applied to cancer survivors who underwent palliative care.
Keywords: Cancer survivors, Outcome assessment, Palliative care, Psychometrics, Quality of life
Table 1 . Fit statistics of the EQ-5D in descending order of difficulty.
EQ-5D | Difficulty | Infit MnSq | Infit ZSTD | Outfit MnSq | Outfit ZSTD |
---|---|---|---|---|---|
EQ-5D 4 pain/discomfort | 52.94 | 0.84 | –1.2 | 0.85 | –1.1 |
EQ-5D 3 usual activities | 51.33 | 0.74 | –2.2 | 0.64 | –2.9 |
EQ-5D 1 mobility | 44.25 | 0.97 | –0.1 | 1.12 | 0.6 |
EQ-5D 5 anxiety/depression | 43.37 | 1.66 | 4.1 | 1.53 | 3.5 |
EQ-5D 2 self-care | 32.87 | 0.64 | –2.0 | 0.46 | –1.8 |
EQ-5D, EuroQOL-5 dimension; MnSq, mean square standardized residuals; ZSTD, Z score standardized..
Table 2 . Fit statistics of the WHOQOL-BREF in descending order of difficulty.
WHOQOL | Difficulty | Infit MnSq | Infit ZSTD | Outfit MnSq | Outfit ZSTD |
---|---|---|---|---|---|
WHOQOL 4 Dependence of medical aids | 53.39 | 1.59 | 4.7 | 1.89 | 6.4 |
WHOQOL 21 Sexual activity | 53.20 | 0.98 | –0.1 | 1.03 | 0.3 |
WHOQOL 18 Work capacity | 51.74 | 0.88 | –1.1 | 0.84 | –1.4 |
WHOQOL 14 Leisure activity | 51.54 | 1.10 | 0.9 | 1.08 | 0.7 |
WHOQOL 12 Financial support | 50.49 | 1.08 | 0.7 | 1.13 | 1.0 |
WHOQOL 16 Sleep and rest | 50.09 | 1.30 | 2.6 | 1.43 | 3.4 |
WHOQOL 11 Bodily image | 49.31 | 0.93 | –0.6 | 0.93 | –0.6 |
WHOQOL 5 Positive feeling | 48.80 | 0.86 | –1.3 | 1.03 | 0.3 |
WHOQOL 10 Energy for daily life | 48.77 | 0.82 | –1.6 | 0.80 | –1.6 |
WHOQOL 13 Accessibility of information | 48.08 | 0.96 | –0.3 | 0.95 | –0.4 |
WHOQOL 17 Activities of daily living | 47.68 | 0.70 | –3.0 | 0.73 | –2.6 |
WHOQOL 8 Security | 47.16 | 0.82 | –1.5 | 0.81 | –1.5 |
WHOQOL 23 Home environment | 46.96 | 1.02 | 0.2 | 1.05 | 0.5 |
WHOQOL 19 Self-esteem | 46.88 | 0.70 | –2.8 | 0.70 | –2.8 |
WHOQOL 15 Mobility | 45.93 | 0.87 | –1.2 | 0.84 | –1.3 |
WHOQOL 9 Physical environment | 45.84 | 0.92 | –0.6 | 0.90 | –0.7 |
WHOQOL 22 Social support | 44.02 | 1.16 | 1.3 | 1.16 | 1.2 |
WHOQOL 7 Concentration | 43.51 | 1.07 | 0.6 | 1.06 | 0.5 |
WHOQOL 3 Pain | 43.39 | 1.22 | 1.8 | 1.41 | 2.7 |
WHOQOL 20 Personal relationship | 42.22 | 0.81 | –1.6 | 0.81 | –1.6 |
WHOQOL 6 Personal belief | 41.90 | 1.09 | 0.8 | 1.07 | 0.5 |
WHOQOL 26 Negative feeling | 40.47 | 1.30 | 2.1 | 1.56 | 3.3 |
WHOQOL 24 Health care | 39.63 | 0.95 | –0.3 | 0.93 | –0.5 |
WHOQOL 25 Transport | 39.06 | 0.88 | –0.9 | 0.88 | –0.9 |
WHOQOL-BREF, World Health Organization Quality of Life; MnSq, mean square standardized residuals; ZSTD, Z score standardized..
Table 3 . Item difficulty of the WHOQOL-BREF in descending order of difficulty.
Item | Difficulty (logits) | Difficulty (logits) | Item |
---|---|---|---|
EQ-5D 4 | 52.94 | 58.52 | WHOQOL 18 |
EQ-5D 3 | 51.33 | 56.99 | WHOQOL 12 |
EQ-5D 1 | 44.25 | 49.82 | WHOQOL 9 |
EQ-5D 5 | 43.37 | 45.08 | WHOQOL 3 |
EQ-5D 2 | 32.87 | 39.59 | WHOQOL 24 |
WHOQOL-BREF, World Health Organization Quality of Life; EQ-5D, EuroQOL-5 dimension..