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Validation of the EQ-5D questionnaire in burn injured adults
burns 35 (2009) 723–732
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Validation of the EQ-5D questionnaire in burn injured adults Caisa O¨ster a, Mimmie Willebrand a, Johan Dyster-Aas a, Morten Kildal b, Lisa Ekselius a,* a b
Department of Neuroscience Psychiatry, University Hospital, SE-751 85 Uppsala, Sweden Department of Surgical Sciences, Plastic Surgery and Burn Center, University Hospital, SE-751 85 Uppsala, Sweden
article info
abstract
Article history:
Background: Health-related quality of life (HRQoL) is an important aspect of adaptation after
Accepted 17 November 2008
burn. The EQ-5D is a standardized generic instrument for assessing HRQoL. Its psychometric properties in a group of burn injured individuals are, however, not known.
Keywords:
Methods: Seventy-eight consecutive patients admitted to a burn unit were included in a
Psychometrics
prospective longitudinal study. The participants completed the EQ-5D during acute care,
EQ-5D
and at 3, 6, and 12 months after the burn. At 6 and 12 months after the burn they also
Health-related quality of life
completed the Short-Form 36 Health Survey (SF-36) and the Burn Specific Health Scale-Brief
Burn injury
(BSHS-B).
Outcome assessment
Results: High feasibility of the EQ-5D was demonstrated through a high response rate and a low proportion of missing or invalid answers. The floor and ceiling effects were small. Construct validity was demonstrated through good differentiation between health states and good discrimination of health states over time. The EQ-5D was associated with burn severity and discriminated between clinical subgroups in an expected manner. Criterion validity was demonstrated through significant correlations between the EQ-5D and subscales of the SF-36 and the BSHS-B. Conclusions: The EQ-5D has good psychometric properties, it is short and easy to administer and thus useful in assessment of HRQoL after burn. # 2008 Elsevier Ltd and ISBI. All rights reserved.
1.
Introduction
Being afflicted with an extensive burn is one of the most catastrophic events an individual can experience. A severe burn is a life threatening state and affects all main integrating systems in the body [1]. Acute care involves both pain and stress [2,3]. Furthermore, the incident can have social consequences such as injured relatives, or even loss of family members as well as loss of property. The process of rehabilitation often continues for many years after the burn and involves physical, psychological and social demands [2,4–6]. Even with optimal treatment, scarring is inevitable after deep burns, and permanent changes in appearance and physical function can occur [7,8]. In addition to functional status, patient-based outcome measures
are important aspects of outcome when evaluating processes of rehabilitation and adaptation after burn [6,9–11]. Patient-based outcomes in burned injured adults have been referred to and reported as perceived health, quality of life (QoL) and/or healthrelated quality of life (HRQoL) [11–22]. Health-related quality of life is a subjective measure of well-being, and can be defined as the individual’s perception of physical, mental and social health over time [23]. Assessment of HRQoL comprises the individual’s perception of his or her injury or illness and how this interferes with the ability to live a fulfilling life [24]. Instruments used to measure HRQoL may be diseasespecific or generic. Disease-specific instruments focus on certain aspects of a given disease. The most well known disease-specific
* Corresponding author. ¨ ster), [email protected] (M. Willebrand), E-mail addresses: [email protected] (C. O [email protected] (J. Dyster-Aas), [email protected] (M. Kildal), [email protected] (L. Ekselius). 0305-4179/$36.00 # 2008 Elsevier Ltd and ISBI. All rights reserved. doi:10.1016/j.burns.2008.11.007
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instrument for use in burn care is the Burn Specific Health Scale (BSHS), developed in 1982 [25] and revised several times [26,27]. The latest version is the Burn Specific Health Scale-Brief (BSHSB), which has undergone more psychometrically evaluation than previous versions [28,29]. BSHS-B captures burn-related health in nine subscales, simple abilities, hand function, heat sensitivity, treatment regimens, body image, affect, interpersonal relationships, sexuality and work. Generic HRQoL instruments are designed to reflect a spectrum of core concepts of HRQoL that may apply to different diseases and populations. Generic instruments can also be used to assess the impact of a disease on HRQoL in comparison with the HRQoL of the general population. One such instrument is the widely used Short-Form 36 Health Survey (SF-36), which captures both physical and mental health phenomena in the eight subscales physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional and mental health [30]. SF-36 has also been used in studies of HRQoL after burn [11–15,31]. Another generic instrument is the EQ-5D, which consists of five dimensions: mobility, self-care, usual activities, pain and anxiety/depression. The EQ-5D provides three different measures: a descriptive health profile, a self-rated health status using a Visual Analogue Scale (VAS) and a summarized index [32,33]. The index can be used as the qualitative weight when computing a quality-adjusted life-year. Recently, EQ-5D was used to calculate the total cost of specialized burn care [34]. Van Beeck and colleagues [35] recently proposed the use of EQ-5D in studies on injury-related disability. However, according to a review published in 2006, there is limited use of HRQoL instruments in burn recovery studies [6], and development and evaluation of such instruments is scarce [36]. No previous study has been found that focuses on validation of the EQ-5D in a population of adults with burn injury. Thus, the aim of this study was to analyze the psychometric properties of the generic instrument EQ-5D in the assessment of HRQoL after burns. Based on clinical experience and the burn literature [11,13,14,37] we hypothesized that EQ-5D would show a lower perceived HRQoL in individuals with bigger burns than in individuals with smaller burns but that such differences would fade over time [11,19,20]. Based on previous information [38,39] we further hypothesized that EQ-5D would report lower perceived HRQoL at 12 months in the subgroup with psychiatric morbidity prior to the burn or in those non-working after the burn [15].
2.
Materials and methods
2.1.
Participants
This study is part of an ongoing prospective longitudinal study concerning physical and psychological outcome after burn trauma. The study was conducted at the Uppsala Burn Unit, one of two national burn units in Sweden. Consecutive burn patients admitted to the Burn Unit between March 2000 and March 2006 were included if they were (1) 18 years of age or older, (2) Swedish speaking, (3) without documented mental retardation or dementia, and (4) had 5% total body surface area (TBSA) burned or a length of stay at the Burn Unit of more
than one day. Patients admitted on a temporary basis who had their main care provided elsewhere were not included.
2.2.
Instruments
2.2.1.
EQ-5D
The EQ-5D was developed by the EuroQol Group, an international, cross-disciplinary group that was set up in 1987 to investigate issues related to the evaluation of health. It has been translated to more than 60 languages, is used worldwide [33] and has previously been used in Swedish populations [40,41]. The reliability and validity of EQ-5D have been documented, both in general [32] and in disease-specific populations [42–44]. The EQ-5D descriptive system encompasses five questions covering five dimensions: mobility, self-care, usual activities, pain and anxiety/depression. For each dimension, respondents value their health by reporting whether they are experiencing 1 = ‘‘none’’, 2 = ‘‘moderate’’ or 3 = ‘‘extreme problems’’. A unique EQ-5D health state is defined by combining the responses (1, 2 or 3) on each of the five dimensions. Thus, the best health state is 11111, the worst is 33333 and the total number of different health states is 35 = 243. The EQ VAS is a vertical 20-cm line graded from 0 = ‘‘worst possible health state’’ to 100 = ‘‘best possible health state’’, on which the respondent is asked to mark his or her own current state of health [33]. The EQ-5D health state can also be converted into a weighted index. The conversion into the index is based on norm values obtained in population-based enquiries [45]. The EQ-5D index ranges from 0.594 = ‘‘death or worse than death’’ to 1 = ‘‘full health’’.
2.2.2.
The Short-Form 36 Health Survey (SF-36)
The SF-36 consists of 36 items divided into eight subscales: physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional and mental health. The raw scores of the eight subscales are transformed and the final scores for each category range from 0 (lowest) to 100 (highest) [30]. The SF-36 has demonstrated acceptable validity in a Swedish population [46].
2.2.3.
Burn Specific Health Scale-Brief (BSHS-B)
The BSHS-B is a 40-item questionnaire with nine subscales: simple abilities, hand function, heat sensitivity, treatment regimens, body image, affect, interpersonal relationships, sexuality and work. Responses to the items are made on a five-point scale ranging from 0 = all the time/great difficulty to 4 = never/no difficulty. Mean scores are calculated for each subscale and high scores indicate a good perceived health status [28]. The BSHS-B has shown good internal consistency and intelligible associations with measures of burn severity, socio-demographics [19], personality traits [37] and coping strategies [47,48].
2.2.4. Structured Clinical Interview for DSM-IV axis I disorders (SCID I) The Structured Clinical Interview for DSM-IV axis I disorders (SCID I) [49] is one of the most widely used and thoroughly researched clinical interviews designed to assess psychiatric disorders. In the present study the SCID I was used to assess the presence of lifetime psychiatric disorders prior to the burn.
burns 35 (2009) 723–732
2.3.
Data collection procedure
The participants answered the EQ-5D during acute care (baseline) and at three, 6 and 12 months after the burn. During acute care, a member of the research team administered the questionnaire. This was done as soon as the patient’s medical condition allowed and the patient was devoid of cognitive dysfunction. At 3, 6 and 12 months, data were collected by postal questionnaires. At six and 12 months the SF-36 and BSHS-B questionnaires were also included. Non-responders received one reminder letter and relevant questionnaires. The SCID I was carried out at baseline by trained professionals (authors M.W. and J.D.A). Details of the procedure are found elsewhere [39]. Information about age, gender, burn size and length of stay was obtained from medical records. In order to achieve a valid score for burn size, TBSA and total body area full-thickness burns (TBSA-FT) were re-assessed by two experienced burn surgeons who used all available medical records, including encompassing photographs and the surgeon’s notes, covering the entire time in care. Evaluations were done separately by the two surgeons and a final burn score was established. Before commencing the project a number of co-rating meetings were held to standardize the evaluation. There was a high agreement between two specialists in assessing the size of the burn. The limit of agreement expressed as the absolute difference between the two observers with the greatest difference was 0.5 (95% confidence interval 2.5) percent surface area for the total burn size and 1.7 (95% confidence interval 6.5) percent for the full-thickness burn. Information about working status was obtained by questionnaire at 12 months post burn. The study was performed according to the Helsinki Declaration [50] and was approved by the Uppsala University Ethics committee.
2.4.
Psychometric analyses
Feasibility was examined by: The response rate and the proportion of missing answers for the EQ-5D. Construct validity was examined by:
The ability of the EQ-5D to differentiate between health states as indicated by the distribution of health states and EQ VAS values. This is also indicated by the mean and median values at different time points and by small or moderate floor and ceiling effects, i.e. the proportion of participants scoring the lowest and the highest possible value, respectively. The ability of the EQ-5D to discriminate between health states over time. This is indicated by changes in the response levels in the five EQ-5D dimensions as a function of time after the burn. The ability of the EQ-5D to discriminate between different levels of burn severity and between clinically relevant subgroups. Criterion validity was examined by:
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Correspondence between EQ-5D responses and the relevant subscales of SF-36 and BSHS-B at 12 months. For the EQ-5D descriptive system, median scores for the SF-36 and the BSHS-B were categorized according to the three response levels in the EQ-5D and compared in non-parametric ANOVA. For the EQ-5D index and EQ VAS scores, correspondence was assessed in rank correlation analyses with the subscale scores of the SF-36 and BSHS-B at 6 and 12 months.
2.5.
Statistical analyses
Non-parametric analyses were used since the data were not normally distributed. The statistical analyses included the Mann–Whitney U-test, the Kruskal–Wallis test and, for categorical data, the Chi-square test. Fisher’s exact test was applied when the expected number of observations was less than 5 in each cell. Correlations were assessed by Spearman rank correlation. Statistical significance was set at p < 0.05. In some presentations percentage was applied although the total numbers were small. Missing values for BSHS-B subscales were approximated when 50 of the items in the subscales were completed, using the mean values of the remaining items of the subscale and missing values for the SF-36 subscales were approximated according to the SF-36 guidelines [46]. See Section 3.1 for EQ-5D missing values.
3.
Results
Of the 95 patients who fulfilled the study criteria, two were missed due to administrative reasons and 15 declined participation, leaving 78 participants (82%) for analysis. There were no significant differences between the 78 participants and the 17 non-participants with respect to age, sex, burn size, or length of hospital stay. The 78 participants included 17 females and 61 males with a mean age of 43.6 years (range: 19–89; SD = 15.1). The mean TBSA was 24.3% (SD = 19.7) of which 10.3% (SD = 14.0) comprised fullthickness burns (TBSA-FT). The average length of stay in the Burn Unit was 25.5 days (SD = 31.2). Sixty-two participants had thermal burns, eight had scalds, seven had electrical burns and one had a chemical burn. Twenty burn injuries were occupational and nine were self-inflicted. Fifty-three participants were employed at the time of the burn, five were students, three were unemployed, 10 were on sick leave or had disability pensions, and seven were retired due to age. Forty-eight of the participants had a lifetime psychiatric disorder prior to the burn. During the first 12 months, one participant had emigrated and one had died, leaving 76 participants for analysis at the 12-month follow-up.
3.1.
Feasibility
At baseline all 78 patients filled in the EQ-5D questionnaire. At 3, 6 and 12 months the response rate was 96%, 94% and 89%, respectively. At 6 months the response rate for both SF-36 and BSHS-B was 94%, and at 12 months it was 89% (SF-36) and 92% (BSHS-B).
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The percentage of missing or invalid responses in the EQ5D descriptive system was almost zero at all four assessments (one missing item at 6 months). The only missing item was substituted by the value of the item typical for the participant (i.e. the participant had scored the same value 3 months before and 3 months after the missing value). For the EQ VAS there were three missing or invalid responses at baseline, one at 3 months, and two at 6 and 12 months, respectively. The missing responses for EQ VAS were not substituted. Ten percent of the SF-36 questionnaires had missing or invalid responses at 6 months, and this was the case for 15% at 12 months. For the BSHS-B questionnaire, 11% and 16% had missing or invalid responses at 6 and 12 months, respectively. The majority (70%) of the missing or invalid responses for the SF-36 and the BSHS-B consisted of just one item per instrument. Concerning missing items of the SF-36 and the BSHS-B see Section 2.5.
3.2. The ability of EQ-5D to differentiate between health states The participants’ valuation of health in the EQ-5D descriptive system resulted in 37 different health states at baseline and 27 health states at 12 months. These combinations constitute 14% and 11%, respectively, of all 243 possible health states. The most common health states at baseline were 22321 (n = 6), 22322 (n = 6), 22233 (n = 5) and 33321 (n = 5), and at 12 months the most common were 11111 (n = 13), 11122 (n = 9) and 11222 (n = 7). Almost 40% of the perceived health states at baseline rendered EQ index values below zero. At 12 months this proportion was 3%. The valuation of health on the EQ VAS scale resulted in 27 different values at baseline and 33 at 12 months. Thirty percent of the EQ VAS values were 35 or lower at baseline. At 12 months this proportion was 6% (data not shown). The mean and median scores for the EQ-5D index and the EQ VAS at different time points after burn are shown in Table 1. At baseline 2.6% showed a floor effect in the EQ-5D, i.e. the proportion of participants who scored the worst possible health state, and 4.0% showed the same in the EQ VAS. At 12 months 19.1% showed a ceiling effect in the EQ5D, i.e. the proportion of participants who scored the best health state, and 4.5% showed a ceiling effect on the EQ VAS (Table 1).
3.3.
The ability of EQ-5D to discriminate over time
The distribution of response levels in each dimension in the EQ-5D descriptive system is shown in Fig. 1. At baseline the majority of the participants indicated moderate or severe problems in all dimensions, but this was not so pronounced regarding the dimension anxiety/depression. At 12 months very few reported problems in the dimensions mobility, selfcare and usual activities, but almost half of the participants reported moderate or extreme problems in the dimensions pain and anxiety/depression.
3.4. Discriminative ability between levels of burn severity and between subgroups Individuals with bigger burns reported moderate or extreme problems at baseline to a greater extent than individuals with smaller burns (Table 2). This was significant for all dimensions except anxiety/depression. At 6 months the difference in reporting problems was shown in two dimensions: self-care and pain. At 12 months there were no differences in reporting problems with respect to burn size. Longer length of stay was associated with more problems at 3 and 6 months, and this was significant for all dimensions except usual activities at 6 months (data not shown). At 12 months longer length of stay was associated with more problems in mobility and pain. The non-working group reported more problems in all five dimensions at 12 months (Table 3). Finally, the subgroup with a psychiatric disorder prior to the burn reported more problems regarding the dimension anxiety/depression at all time points and more problems with respect to the dimension usual activities at baseline (only 12-month assessment shown in Table 3).
3.5.
Criterion validity
Table 4 presents the median scores for the relevant SF-36 and BSHS-B subscales at 12 months categorized according to the level of response in the comparable EQ-5D dimensions. Different response levels in the EQ-5D dimensions were significantly associated with median scores in the presented subscales of SF-36 and BSHS-B. A similar pattern was found at 6 months except for a group of participants also scoring extreme problems in the dimension mobility (data not shown). The correlation coefficients between the EQ-5D index and the SF-36 subscales at 6 and 12 months were in the range of
Table 1 – Mean, median and floor/ceiling effects of the EQ-5D index and EQ VAS at different assessment time points. Mean score (SD)
EQ-5D index Median (interquartile range)
Baseline 3 months 6 months 12 months
0.14 0.51 0.54 0.67
(0.37) (0.36) (0.36) (0.28)
0.14 0.66 0.66 0.73
(0.10 to 0.33) (0.30–0.76) (0.26–0.80) (0.62–0.84)
Mean score (SD)
Floor/ceiling effect (%) 2.6/2.6 0/9.7 0/12.3 0/19.1
EQ VAS Median (interquartile range)
48.9 65.9 65.2 70.3
(24.2) (21.5) (22.7) (21.5)
Owing to missing values, comparisons were based on different sample sizes varying between 67 and 78.
50.0 70.0 70.0 72.0
(30.0–70.0) (50.0–85.0) (50.0–83.8) (60.0–88.0)
Floor/ceiling effect (%) 4.0/0 0/1.4 1.4/4.2 1.5/4.5
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Fig. 1 – Distribution of responses to items of the EQ-5D questionnaire at baseline, and at 3, 6 and 12 months, n = 65 (all participants who answered the questionnaire at all assessment time points).
Table 2 – The ability of the EQ-5D to discriminate between different levels of burn severity at different assessment time points. TBSAa Baseline
TBSA-FTb
3 months
6 months 12 months Baseline
LOSc
3 months 6 months 12 months 12 months
EQ-5D dimension Mobility No Moderate Extreme
**
ns 16 (7–32) 14 (4–50) 45 (32–73)
ns 16 (7–31) 43 (6–54) 31d
ns 17 (9–35) 25 (7–59)
***
**
0 (0–7) 3 (1–7) 19 (7–33)
3 (0–7) 9 (1–27) 43 (26–60)
ns 4 (0–9) 10 (1–33) 23d
ns 5 (0–13) 9 (1–33)
*
14 (7–19)d 17 (7–31) 34 (15–52)
Self- Care No Moderate Extreme
***
***
*
***
**
15 (7–24) 31 (14–56) 3 (7–59)
16 (7–33) 30 (16–50) 66e
ns 17 (8–36) 25 (8–52)
***
9 (5–16) 18 (8–34) 30 (14–48)
0 (0–5) 4 (1–12) 9 (3–23)
2 (0–6) 10 (4–33) 24 (6–53)
3 (0–9) 18 (3–28) 57e
ns 5 (1–13) 3 (0–28)
ns 18 (7–29) 23 (9–60)
Usual activities No Moderate Extreme
***
***
***
9 (5–18) 15 (8–24) 34 (16–52)
ns 17 (9–35) 22 (5–42) 24 (16–52)
**
13 (5–18) 11 (6–16) 24 (10–40)
ns 16 (7–30) 17 (9–41) 25 (15–53)
1 (0–5) 2 (0–6) 7 (1–22)
1 (0–5) 4 (1–10) 10 (3–29)
ns 5 (0–7) 3 (1–12) 13 (2–33)
ns 5 (0–11) 5 (0–28) 6 (2–38)
ns 17 (6–27) 24 (9–35) 27 (13–92)
Pain No Moderate Extreme
***
***
*
***
*
12 (7–19) 18 (7–41) 34 (16–53)
2 (0–6) 4 (1–9) 21 (1–31)
0 (0–5) 4 (1–10) 28 (20–43)
4 (0–7) 3 (1–13) 21 (7–31)
ns 5 (0–8) 6 (2–23) 1 (0–20)
*
16 (7–19) 16 (7–35) 52 (32–55)
ns 14 (7– 0) 24 (11–48) 14 (6–43)
*
15 (7–21) 16 (7–31) 36 (16–52)
Anxiety/depression No Moderate Extreme
ns 15 (6–29) 24 (10–46) 24 (17–39)
ns 15 (7–35) 17 (10–36) 30 (15–49)
ns 14 (7–33) 19 (11–41) 17 (10–53)
ns 16 (7–41) 18 (12–35) 17 (7–52)
ns 3 (0–7) 7 (1–25) 2 (1–20)
ns 4 (0–8) 3 (1–27) 14 (5–25)
ns 4 (0–7) 5 (1–20) 9 (2–36)
ns 4 (0–11) 6 (1–18) 9 (3–43)
ns 12 (6–28) 24 (11–34) 19 (11–91)
ns = Not significant. p-value < 0.05, Kruskal–Wallis test, median (interquartile range). ** p-value < 0.01, Kruskal–Wallis test, median (interquartile range). *** p-value < 0.001, Kruskal–Wallis test, median (interquartile range). a Total body surface area burned. b Total body area full-thickness burns. c Length of stay. d n = 1. e n = 2. *
18 (9–27) 43 (6–54)
12 (5–26) 23 (11–46) 11 (4–51)
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Table 3 – The ability of the EQ-5D to discriminate between clinically relevant subgroups. At work 12 months Yes
Preburn psychiatric disorder 12 months No
Yes
No
24 (67) 12 (33) 0
ns 26 (84) 5 (16) 0
26 (72) 9 (25) 1 (3)
ns 1 27 (87) 3 (19) 1 (3)
16 (44) 11 (31) 9 (25)
ns 1 19 (61) 8 (26) 4 (13)
22 (60) 10 (27) 5 (13)
6 (17) 26 (72) 4 (11)
ns 1 10 (32) 20 (64) 1 (3)
11(30) 23 (62) 3 (8)
EQ-5D dimension Mobility No Moderate Extreme Self- Care No Moderate Extreme
**
30 (94) 2 (6) 0 ***1
32 (100) 0 0 **1
Usual activities No Moderate Extreme
25 (78) 7 (22) 0
Pain No Moderate Extreme
15 (47) 17 (53) 0
Anxiety/depression No Moderate Extreme
18 (56) 13 (41) 1(3)
**1
*1
28 (76) 9 (24) 0
31 (84) 6 (16)
**1
12 (33) 20 (56) 4 (11)
8 (26) 19 (61) 4 (13)
22 (60) 14 (38) 1 (2)
x2 test, numbers (percentage), 1Fisher’s Exact Test due to small expected cell counts. ns = not significant. p-value < 0.01. ** p-value < 0.001. *** p-value < 0.05. *
Table 4 – Association between the subscales of the SF-36 and BSHS-B and the relevant EQ-5D dimensions by response level at 12 months. EQ-5D dimension
EQ-5D response level No problem
Mobility Mobility Self-care Self-care Usual activities Usual activities Pain Anxiety/depression Anxiety/depression Anxiety/depression
SF-36 subscale Physical functioning Role functioning Physical functioning Role functioning General health Social functioning Bodily pain Vitality Role emotional Mental health
Mobility Self-care Self-care Usual activities Usual activities Pain Anxiety/depression Anxiety/depression Anxiety/depression
BSHS-B subscale Simple ability Hand function Treatment regimens Simple abilities Work Heat sensitivity Affect Interpersonal relationships Sexuality
83 68 83 55 77 100 100 75 100 88
(74–100) (0–100) (65–100) (0–100) (60–92) (63–100) (84–100) (63–85) (100–100) (83–95)
4.0 4.0 3.0 4.0 3.0 2.6 3.8 4.0 4.0
(3.7–4.0) (3.6–4.0) (2.2–3.8) (3.8–4.0) (2.1–3.9) (1.6–3–6) (3.2–4.0) (3.9–4.0) (3.6–4.0)
Moderate problem 40 0 45 0 68 69 51 40 33 60
(30–58) (0–0) (33–65) (0–13) (50–76) (59–91) (41–74) (30–63) (0–67) (52–72)
3.0 2.8 2.0 4.0 1.5 1.6 2.9 3.5 3.0
(2.0–3.8) (1.2–3.6) (1.1–2.9) (3.3–4.0) (0.8–2.4) (0.6–2.6) (2.3–3.3) (3.0–4.0) (2.3–4.0)
Extreme problem – – 70 0 31 30 22 30 0 24
(70–70) (0–0) (20–64) (1–50) (15–22) (18–45) (0–17) (14–32)
– 3.8 0.8 3.0 0.0 0.3 0.7 2.3 2.0
(3.8–3.8) (0.8–0.8) (1.7–3.7) (0.0–0.8) (0.2–0.7) (0.3–1.8) (0.8–3.1) (0.7–4.0)
py <0.0001 0.004 0.001a 0.017a 0.002 <0.0001 <0.0001 0.002 <0.0001 <0.0001
<0.0001 <0.0001a 0.011a 0.001 <0.0001 0.003 <0.0001 <0.0001 0.019
Data are medians (interquartile range). Comparisons were made with different sample sizes varying from 71 to 72 (owing to missing values). y The Kruskall–Wallis test was used for comparison of distribution between groups. a The categories moderate and extreme problems were collapsed into one category for significance tests when the category extreme problems <5.
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Table 5 – Spearman rank correlations of EQ VAS and the EQ-5D index with subscales of SF-36 and BSHS-B. 6 months
12 months
EQ-5D index
EQ VAS
EQ-5D index
EQ VAS
SF-36 subscale Physical functioning Role functioning Bodily pain General health Vitality Social functioning Role emotional Mental health
0.61 0.73 0.63 0.69 0.78 0.65 0.62 0.62
0.66 0.58 0.53 0.76 0.76 0.69 0.48 0.75
0.58 0.60 0.64 0.57 0.62 0.59 0.57 0.55
0.72 0.67 0.54 0.77 0.63 0.53 0.46 0.46
BSHS-B subscale Simple abilities Heat sensitivity Hand function Treatment regimens Work Body image Affect Interpersonal relationship Sexuality
0.57 0.38 0.34 0.61 0.69 0.57 0.59 0.34 0.33
0.56 0.32 0.33 0.43 0.47 0.42 0.60 0.38 0.36
0.52 0.43 0.41 0.32 0.64 0.41 0.52 0.47 0.26*
0.54 0.41 0.51 0.37 0.45 0.44 0.53 0.50 0.48
Owing to missing values, comparisons were based on different sample sizes varying between 66 and 72. All coefficients are significantly different from zero, all other p-values < 0.01 (except p-value < 0.05). * p-value < 0.05.
0.55–0.78 (Table 5) and the correlations with the BSHS-B subscales ranged from 0.26 to 0.69. The correlation coefficients between the EQ VAS scores and the SF-36 and BSHS-B subscales ranged from 0.32 to 0.77. All coefficients were significantly different from zero.
4.
Discussion
The aim of the present study was to analyze the psychometric properties of the EQ-5D in burn-injured adults. The low proportion of missing or invalid responses for the questionnaires shows that the instrument is well understood and accepted in adults with burns, and indicates good feasibility. The EQ-5D and EQ VAS showed small floor and ceiling effects at all time points. The high proportion of individuals who perceived poor HRQoL at baseline, as indicated by an index below zero (‘‘death or worse than death’’) [45], seems to reflect that a severe burn is a devastating event that affects quality of life in all respects. The mean index values and the VAS scores improved in an expected manner between the first and last assessments. Mean values at 12 months were in line with those reported after other types of injury-related trauma [51–53], but markedly below the Swedish general population index [54]. This study suggests that rehabilitation after burn is a protracted process that continues beyond the first year after the burn, which is in line with previous long-term studies of burn-specific health [19]. Results concerning HRQoL after burns are contradictory. While some suggest that burn survivors as a group do not differ from the general population [12,13,31], others point to burn-specific physical as well as
psychological problems [11,14,15]. Our results lend support to the latter suggestion. In the present study only a small group of participants reported problems at 12 months in the dimensions mobility, self-care and usual activities, whereas almost half of them still perceived problems in the dimensions pain and anxiety/ depression. No comparable studies of EQ-5D in burn patients could be found. However, after other forms of severe trauma, researchers observed a pattern characterized by fewer problems in the anxiety/depression dimension than in our study [53,55]. A reasonable explanation for the high proportion of problems in the anxiety/depression dimension among our burn survivors may be that a group of patients afflicted by burns seems to have a psychiatric history and that such a history constitutes a risk factor for post-burn psychiatric morbidity [38,39]. Moreover, it has recently been demonstrated that the EQ-5D has the ability to identify clinical symptoms of anxiety and/or depression in a population screening [56]. As hypothesized, the EQ-5D distinguished between different levels of burn severity in an expected manner. At baseline, burn size influenced all dimensions of EQ-5D negatively except anxiety/depression, but at 12 months this effect had faded away. Longer length of stay at the Burn Unit influenced almost all dimensions negatively during the first year after burn. At 12 months, longer length of stay was still associated with more problems in the dimensions mobility and pain. This seems logical, as a longer stay in intensive care is often related to complications, which might affect long-term physical function and pain. Furthermore, the group of participants who were not working at 12 months after the burn reported significantly lower HRQoL in all dimensions as compared to those who were working. This is
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compatible with findings reported by others [11,15]. In addition, psychiatric morbidity prior to the burn was only associated with more problems in the dimension anxiety/ depression at 12 months. However, in a previous study using a disease-specific instrument, preburn psychiatric morbidity influenced perceived physical as well as psychological health negatively after the burn [38]. As generic and disease-specific measures capture somewhat different health aspects [23,24], their combined use has been recommended in the evaluation of health outcome after injury [35] and after burn [6]. Associations between the EQ-5D response levels and relevant subscale scores of the generic SF-36 and the disease-specific BSHS-B indicate that the EQ-5D has reasonable criterion validity. Furthermore, the EQ-5D index and the EQ VAS correlated well with all of the SF-36 subscales. Taken together, this may indicate that the EQ-5D reflects a construct of HRQoL that is similar to that of the SF-36. As expected, the correlations between EQ-5D and the subscales of BSHS-B were somewhat lower than for the SF-36. Sexuality and hand function showed the lowest correlations with both the EQ-5D index and the EQ VAS score which indicates that there is a satisfactory divergent validity as it has previously been shown that bad perceived health with respect to the BSHS-B subscales sexuality and hand function are relatively independent of other reported problems [19]. Limitations of the study were the relatively small sample size and that no formal reliability analysis could be done. Another possible limitation was that the three instruments cover different reference periods. Whereas EQ-5D asks about the current health state, SF-36 asks about the last 4 weeks and BSHS-B has no specific time frame. In the rehabilitation period after burn, dynamic changes in HRQoL sometimes occur over several weeks, which might have led to differences in the comparative assessments. In addition, this study was conducted on in-patients, i.e. with a certain burn severity. It can therefore not lend itself to support the use of EQ-5D in small burns that are handled as out-patients only. Furthermore, the results of this study may not apply to other geographical locations and cultural backgrounds even though the instruments are widely used in many countries around the world. Finally, the specific handling of patients during and after the injury at one particular burn unit may have an impact on the perceived HRQoL, which would further limit generalization. However, this issue cannot find an answer in the present study. Strengths of the study include repeated assessments during a period of 12 months, as well as comparisons with generic and disease-specific instruments. The prospective design with the use of a structured interview and validated burn characteristics suggest a high clinical validity.
5.
Conclusion
Overall, the EQ-5D showed good psychometric properties. The descriptive system, the EQ VAS and the EQ index are useful tools for describing aspects of HRQoL after burn injury, and for comparing outcomes with other trauma or diseases.
Further, the EQ-5D is short and easy to administer. Taken together, the results of this study support the use of the EQ-5D in burn injured adults as an adjunct to burn-specific instruments.
Conflict of interest There are no conflicts of interest to declare.
Acknowledgments This research was supported by the Swedish Research Council and the Swedish Council for Working Life and Social Research. The authors would like to thank Professor Bengt Gerdin, Department of Surgical sciences, Plastic surgery and Burn Unit, University Hospital, Uppsala University for valuable comments in previous versions of the manuscript.
references
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available at www.sciencedirect.com
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Validation of the EQ-5D questionnaire in burn injured adults Caisa O¨ster a, Mimmie Willebrand a, Johan Dyster-Aas a, Morten Kildal b, Lisa Ekselius a,* a b
Department of Neuroscience Psychiatry, University Hospital, SE-751 85 Uppsala, Sweden Department of Surgical Sciences, Plastic Surgery and Burn Center, University Hospital, SE-751 85 Uppsala, Sweden
article info
abstract
Article history:
Background: Health-related quality of life (HRQoL) is an important aspect of adaptation after
Accepted 17 November 2008
burn. The EQ-5D is a standardized generic instrument for assessing HRQoL. Its psychometric properties in a group of burn injured individuals are, however, not known.
Keywords:
Methods: Seventy-eight consecutive patients admitted to a burn unit were included in a
Psychometrics
prospective longitudinal study. The participants completed the EQ-5D during acute care,
EQ-5D
and at 3, 6, and 12 months after the burn. At 6 and 12 months after the burn they also
Health-related quality of life
completed the Short-Form 36 Health Survey (SF-36) and the Burn Specific Health Scale-Brief
Burn injury
(BSHS-B).
Outcome assessment
Results: High feasibility of the EQ-5D was demonstrated through a high response rate and a low proportion of missing or invalid answers. The floor and ceiling effects were small. Construct validity was demonstrated through good differentiation between health states and good discrimination of health states over time. The EQ-5D was associated with burn severity and discriminated between clinical subgroups in an expected manner. Criterion validity was demonstrated through significant correlations between the EQ-5D and subscales of the SF-36 and the BSHS-B. Conclusions: The EQ-5D has good psychometric properties, it is short and easy to administer and thus useful in assessment of HRQoL after burn. # 2008 Elsevier Ltd and ISBI. All rights reserved.
1.
Introduction
Being afflicted with an extensive burn is one of the most catastrophic events an individual can experience. A severe burn is a life threatening state and affects all main integrating systems in the body [1]. Acute care involves both pain and stress [2,3]. Furthermore, the incident can have social consequences such as injured relatives, or even loss of family members as well as loss of property. The process of rehabilitation often continues for many years after the burn and involves physical, psychological and social demands [2,4–6]. Even with optimal treatment, scarring is inevitable after deep burns, and permanent changes in appearance and physical function can occur [7,8]. In addition to functional status, patient-based outcome measures
are important aspects of outcome when evaluating processes of rehabilitation and adaptation after burn [6,9–11]. Patient-based outcomes in burned injured adults have been referred to and reported as perceived health, quality of life (QoL) and/or healthrelated quality of life (HRQoL) [11–22]. Health-related quality of life is a subjective measure of well-being, and can be defined as the individual’s perception of physical, mental and social health over time [23]. Assessment of HRQoL comprises the individual’s perception of his or her injury or illness and how this interferes with the ability to live a fulfilling life [24]. Instruments used to measure HRQoL may be diseasespecific or generic. Disease-specific instruments focus on certain aspects of a given disease. The most well known disease-specific
* Corresponding author. ¨ ster), [email protected] (M. Willebrand), E-mail addresses: [email protected] (C. O [email protected] (J. Dyster-Aas), [email protected] (M. Kildal), [email protected] (L. Ekselius). 0305-4179/$36.00 # 2008 Elsevier Ltd and ISBI. All rights reserved. doi:10.1016/j.burns.2008.11.007
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instrument for use in burn care is the Burn Specific Health Scale (BSHS), developed in 1982 [25] and revised several times [26,27]. The latest version is the Burn Specific Health Scale-Brief (BSHSB), which has undergone more psychometrically evaluation than previous versions [28,29]. BSHS-B captures burn-related health in nine subscales, simple abilities, hand function, heat sensitivity, treatment regimens, body image, affect, interpersonal relationships, sexuality and work. Generic HRQoL instruments are designed to reflect a spectrum of core concepts of HRQoL that may apply to different diseases and populations. Generic instruments can also be used to assess the impact of a disease on HRQoL in comparison with the HRQoL of the general population. One such instrument is the widely used Short-Form 36 Health Survey (SF-36), which captures both physical and mental health phenomena in the eight subscales physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional and mental health [30]. SF-36 has also been used in studies of HRQoL after burn [11–15,31]. Another generic instrument is the EQ-5D, which consists of five dimensions: mobility, self-care, usual activities, pain and anxiety/depression. The EQ-5D provides three different measures: a descriptive health profile, a self-rated health status using a Visual Analogue Scale (VAS) and a summarized index [32,33]. The index can be used as the qualitative weight when computing a quality-adjusted life-year. Recently, EQ-5D was used to calculate the total cost of specialized burn care [34]. Van Beeck and colleagues [35] recently proposed the use of EQ-5D in studies on injury-related disability. However, according to a review published in 2006, there is limited use of HRQoL instruments in burn recovery studies [6], and development and evaluation of such instruments is scarce [36]. No previous study has been found that focuses on validation of the EQ-5D in a population of adults with burn injury. Thus, the aim of this study was to analyze the psychometric properties of the generic instrument EQ-5D in the assessment of HRQoL after burns. Based on clinical experience and the burn literature [11,13,14,37] we hypothesized that EQ-5D would show a lower perceived HRQoL in individuals with bigger burns than in individuals with smaller burns but that such differences would fade over time [11,19,20]. Based on previous information [38,39] we further hypothesized that EQ-5D would report lower perceived HRQoL at 12 months in the subgroup with psychiatric morbidity prior to the burn or in those non-working after the burn [15].
2.
Materials and methods
2.1.
Participants
This study is part of an ongoing prospective longitudinal study concerning physical and psychological outcome after burn trauma. The study was conducted at the Uppsala Burn Unit, one of two national burn units in Sweden. Consecutive burn patients admitted to the Burn Unit between March 2000 and March 2006 were included if they were (1) 18 years of age or older, (2) Swedish speaking, (3) without documented mental retardation or dementia, and (4) had 5% total body surface area (TBSA) burned or a length of stay at the Burn Unit of more
than one day. Patients admitted on a temporary basis who had their main care provided elsewhere were not included.
2.2.
Instruments
2.2.1.
EQ-5D
The EQ-5D was developed by the EuroQol Group, an international, cross-disciplinary group that was set up in 1987 to investigate issues related to the evaluation of health. It has been translated to more than 60 languages, is used worldwide [33] and has previously been used in Swedish populations [40,41]. The reliability and validity of EQ-5D have been documented, both in general [32] and in disease-specific populations [42–44]. The EQ-5D descriptive system encompasses five questions covering five dimensions: mobility, self-care, usual activities, pain and anxiety/depression. For each dimension, respondents value their health by reporting whether they are experiencing 1 = ‘‘none’’, 2 = ‘‘moderate’’ or 3 = ‘‘extreme problems’’. A unique EQ-5D health state is defined by combining the responses (1, 2 or 3) on each of the five dimensions. Thus, the best health state is 11111, the worst is 33333 and the total number of different health states is 35 = 243. The EQ VAS is a vertical 20-cm line graded from 0 = ‘‘worst possible health state’’ to 100 = ‘‘best possible health state’’, on which the respondent is asked to mark his or her own current state of health [33]. The EQ-5D health state can also be converted into a weighted index. The conversion into the index is based on norm values obtained in population-based enquiries [45]. The EQ-5D index ranges from 0.594 = ‘‘death or worse than death’’ to 1 = ‘‘full health’’.
2.2.2.
The Short-Form 36 Health Survey (SF-36)
The SF-36 consists of 36 items divided into eight subscales: physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional and mental health. The raw scores of the eight subscales are transformed and the final scores for each category range from 0 (lowest) to 100 (highest) [30]. The SF-36 has demonstrated acceptable validity in a Swedish population [46].
2.2.3.
Burn Specific Health Scale-Brief (BSHS-B)
The BSHS-B is a 40-item questionnaire with nine subscales: simple abilities, hand function, heat sensitivity, treatment regimens, body image, affect, interpersonal relationships, sexuality and work. Responses to the items are made on a five-point scale ranging from 0 = all the time/great difficulty to 4 = never/no difficulty. Mean scores are calculated for each subscale and high scores indicate a good perceived health status [28]. The BSHS-B has shown good internal consistency and intelligible associations with measures of burn severity, socio-demographics [19], personality traits [37] and coping strategies [47,48].
2.2.4. Structured Clinical Interview for DSM-IV axis I disorders (SCID I) The Structured Clinical Interview for DSM-IV axis I disorders (SCID I) [49] is one of the most widely used and thoroughly researched clinical interviews designed to assess psychiatric disorders. In the present study the SCID I was used to assess the presence of lifetime psychiatric disorders prior to the burn.
burns 35 (2009) 723–732
2.3.
Data collection procedure
The participants answered the EQ-5D during acute care (baseline) and at three, 6 and 12 months after the burn. During acute care, a member of the research team administered the questionnaire. This was done as soon as the patient’s medical condition allowed and the patient was devoid of cognitive dysfunction. At 3, 6 and 12 months, data were collected by postal questionnaires. At six and 12 months the SF-36 and BSHS-B questionnaires were also included. Non-responders received one reminder letter and relevant questionnaires. The SCID I was carried out at baseline by trained professionals (authors M.W. and J.D.A). Details of the procedure are found elsewhere [39]. Information about age, gender, burn size and length of stay was obtained from medical records. In order to achieve a valid score for burn size, TBSA and total body area full-thickness burns (TBSA-FT) were re-assessed by two experienced burn surgeons who used all available medical records, including encompassing photographs and the surgeon’s notes, covering the entire time in care. Evaluations were done separately by the two surgeons and a final burn score was established. Before commencing the project a number of co-rating meetings were held to standardize the evaluation. There was a high agreement between two specialists in assessing the size of the burn. The limit of agreement expressed as the absolute difference between the two observers with the greatest difference was 0.5 (95% confidence interval 2.5) percent surface area for the total burn size and 1.7 (95% confidence interval 6.5) percent for the full-thickness burn. Information about working status was obtained by questionnaire at 12 months post burn. The study was performed according to the Helsinki Declaration [50] and was approved by the Uppsala University Ethics committee.
2.4.
Psychometric analyses
Feasibility was examined by: The response rate and the proportion of missing answers for the EQ-5D. Construct validity was examined by:
The ability of the EQ-5D to differentiate between health states as indicated by the distribution of health states and EQ VAS values. This is also indicated by the mean and median values at different time points and by small or moderate floor and ceiling effects, i.e. the proportion of participants scoring the lowest and the highest possible value, respectively. The ability of the EQ-5D to discriminate between health states over time. This is indicated by changes in the response levels in the five EQ-5D dimensions as a function of time after the burn. The ability of the EQ-5D to discriminate between different levels of burn severity and between clinically relevant subgroups. Criterion validity was examined by:
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Correspondence between EQ-5D responses and the relevant subscales of SF-36 and BSHS-B at 12 months. For the EQ-5D descriptive system, median scores for the SF-36 and the BSHS-B were categorized according to the three response levels in the EQ-5D and compared in non-parametric ANOVA. For the EQ-5D index and EQ VAS scores, correspondence was assessed in rank correlation analyses with the subscale scores of the SF-36 and BSHS-B at 6 and 12 months.
2.5.
Statistical analyses
Non-parametric analyses were used since the data were not normally distributed. The statistical analyses included the Mann–Whitney U-test, the Kruskal–Wallis test and, for categorical data, the Chi-square test. Fisher’s exact test was applied when the expected number of observations was less than 5 in each cell. Correlations were assessed by Spearman rank correlation. Statistical significance was set at p < 0.05. In some presentations percentage was applied although the total numbers were small. Missing values for BSHS-B subscales were approximated when 50 of the items in the subscales were completed, using the mean values of the remaining items of the subscale and missing values for the SF-36 subscales were approximated according to the SF-36 guidelines [46]. See Section 3.1 for EQ-5D missing values.
3.
Results
Of the 95 patients who fulfilled the study criteria, two were missed due to administrative reasons and 15 declined participation, leaving 78 participants (82%) for analysis. There were no significant differences between the 78 participants and the 17 non-participants with respect to age, sex, burn size, or length of hospital stay. The 78 participants included 17 females and 61 males with a mean age of 43.6 years (range: 19–89; SD = 15.1). The mean TBSA was 24.3% (SD = 19.7) of which 10.3% (SD = 14.0) comprised fullthickness burns (TBSA-FT). The average length of stay in the Burn Unit was 25.5 days (SD = 31.2). Sixty-two participants had thermal burns, eight had scalds, seven had electrical burns and one had a chemical burn. Twenty burn injuries were occupational and nine were self-inflicted. Fifty-three participants were employed at the time of the burn, five were students, three were unemployed, 10 were on sick leave or had disability pensions, and seven were retired due to age. Forty-eight of the participants had a lifetime psychiatric disorder prior to the burn. During the first 12 months, one participant had emigrated and one had died, leaving 76 participants for analysis at the 12-month follow-up.
3.1.
Feasibility
At baseline all 78 patients filled in the EQ-5D questionnaire. At 3, 6 and 12 months the response rate was 96%, 94% and 89%, respectively. At 6 months the response rate for both SF-36 and BSHS-B was 94%, and at 12 months it was 89% (SF-36) and 92% (BSHS-B).
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The percentage of missing or invalid responses in the EQ5D descriptive system was almost zero at all four assessments (one missing item at 6 months). The only missing item was substituted by the value of the item typical for the participant (i.e. the participant had scored the same value 3 months before and 3 months after the missing value). For the EQ VAS there were three missing or invalid responses at baseline, one at 3 months, and two at 6 and 12 months, respectively. The missing responses for EQ VAS were not substituted. Ten percent of the SF-36 questionnaires had missing or invalid responses at 6 months, and this was the case for 15% at 12 months. For the BSHS-B questionnaire, 11% and 16% had missing or invalid responses at 6 and 12 months, respectively. The majority (70%) of the missing or invalid responses for the SF-36 and the BSHS-B consisted of just one item per instrument. Concerning missing items of the SF-36 and the BSHS-B see Section 2.5.
3.2. The ability of EQ-5D to differentiate between health states The participants’ valuation of health in the EQ-5D descriptive system resulted in 37 different health states at baseline and 27 health states at 12 months. These combinations constitute 14% and 11%, respectively, of all 243 possible health states. The most common health states at baseline were 22321 (n = 6), 22322 (n = 6), 22233 (n = 5) and 33321 (n = 5), and at 12 months the most common were 11111 (n = 13), 11122 (n = 9) and 11222 (n = 7). Almost 40% of the perceived health states at baseline rendered EQ index values below zero. At 12 months this proportion was 3%. The valuation of health on the EQ VAS scale resulted in 27 different values at baseline and 33 at 12 months. Thirty percent of the EQ VAS values were 35 or lower at baseline. At 12 months this proportion was 6% (data not shown). The mean and median scores for the EQ-5D index and the EQ VAS at different time points after burn are shown in Table 1. At baseline 2.6% showed a floor effect in the EQ-5D, i.e. the proportion of participants who scored the worst possible health state, and 4.0% showed the same in the EQ VAS. At 12 months 19.1% showed a ceiling effect in the EQ5D, i.e. the proportion of participants who scored the best health state, and 4.5% showed a ceiling effect on the EQ VAS (Table 1).
3.3.
The ability of EQ-5D to discriminate over time
The distribution of response levels in each dimension in the EQ-5D descriptive system is shown in Fig. 1. At baseline the majority of the participants indicated moderate or severe problems in all dimensions, but this was not so pronounced regarding the dimension anxiety/depression. At 12 months very few reported problems in the dimensions mobility, selfcare and usual activities, but almost half of the participants reported moderate or extreme problems in the dimensions pain and anxiety/depression.
3.4. Discriminative ability between levels of burn severity and between subgroups Individuals with bigger burns reported moderate or extreme problems at baseline to a greater extent than individuals with smaller burns (Table 2). This was significant for all dimensions except anxiety/depression. At 6 months the difference in reporting problems was shown in two dimensions: self-care and pain. At 12 months there were no differences in reporting problems with respect to burn size. Longer length of stay was associated with more problems at 3 and 6 months, and this was significant for all dimensions except usual activities at 6 months (data not shown). At 12 months longer length of stay was associated with more problems in mobility and pain. The non-working group reported more problems in all five dimensions at 12 months (Table 3). Finally, the subgroup with a psychiatric disorder prior to the burn reported more problems regarding the dimension anxiety/depression at all time points and more problems with respect to the dimension usual activities at baseline (only 12-month assessment shown in Table 3).
3.5.
Criterion validity
Table 4 presents the median scores for the relevant SF-36 and BSHS-B subscales at 12 months categorized according to the level of response in the comparable EQ-5D dimensions. Different response levels in the EQ-5D dimensions were significantly associated with median scores in the presented subscales of SF-36 and BSHS-B. A similar pattern was found at 6 months except for a group of participants also scoring extreme problems in the dimension mobility (data not shown). The correlation coefficients between the EQ-5D index and the SF-36 subscales at 6 and 12 months were in the range of
Table 1 – Mean, median and floor/ceiling effects of the EQ-5D index and EQ VAS at different assessment time points. Mean score (SD)
EQ-5D index Median (interquartile range)
Baseline 3 months 6 months 12 months
0.14 0.51 0.54 0.67
(0.37) (0.36) (0.36) (0.28)
0.14 0.66 0.66 0.73
(0.10 to 0.33) (0.30–0.76) (0.26–0.80) (0.62–0.84)
Mean score (SD)
Floor/ceiling effect (%) 2.6/2.6 0/9.7 0/12.3 0/19.1
EQ VAS Median (interquartile range)
48.9 65.9 65.2 70.3
(24.2) (21.5) (22.7) (21.5)
Owing to missing values, comparisons were based on different sample sizes varying between 67 and 78.
50.0 70.0 70.0 72.0
(30.0–70.0) (50.0–85.0) (50.0–83.8) (60.0–88.0)
Floor/ceiling effect (%) 4.0/0 0/1.4 1.4/4.2 1.5/4.5
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Fig. 1 – Distribution of responses to items of the EQ-5D questionnaire at baseline, and at 3, 6 and 12 months, n = 65 (all participants who answered the questionnaire at all assessment time points).
Table 2 – The ability of the EQ-5D to discriminate between different levels of burn severity at different assessment time points. TBSAa Baseline
TBSA-FTb
3 months
6 months 12 months Baseline
LOSc
3 months 6 months 12 months 12 months
EQ-5D dimension Mobility No Moderate Extreme
**
ns 16 (7–32) 14 (4–50) 45 (32–73)
ns 16 (7–31) 43 (6–54) 31d
ns 17 (9–35) 25 (7–59)
***
**
0 (0–7) 3 (1–7) 19 (7–33)
3 (0–7) 9 (1–27) 43 (26–60)
ns 4 (0–9) 10 (1–33) 23d
ns 5 (0–13) 9 (1–33)
*
14 (7–19)d 17 (7–31) 34 (15–52)
Self- Care No Moderate Extreme
***
***
*
***
**
15 (7–24) 31 (14–56) 3 (7–59)
16 (7–33) 30 (16–50) 66e
ns 17 (8–36) 25 (8–52)
***
9 (5–16) 18 (8–34) 30 (14–48)
0 (0–5) 4 (1–12) 9 (3–23)
2 (0–6) 10 (4–33) 24 (6–53)
3 (0–9) 18 (3–28) 57e
ns 5 (1–13) 3 (0–28)
ns 18 (7–29) 23 (9–60)
Usual activities No Moderate Extreme
***
***
***
9 (5–18) 15 (8–24) 34 (16–52)
ns 17 (9–35) 22 (5–42) 24 (16–52)
**
13 (5–18) 11 (6–16) 24 (10–40)
ns 16 (7–30) 17 (9–41) 25 (15–53)
1 (0–5) 2 (0–6) 7 (1–22)
1 (0–5) 4 (1–10) 10 (3–29)
ns 5 (0–7) 3 (1–12) 13 (2–33)
ns 5 (0–11) 5 (0–28) 6 (2–38)
ns 17 (6–27) 24 (9–35) 27 (13–92)
Pain No Moderate Extreme
***
***
*
***
*
12 (7–19) 18 (7–41) 34 (16–53)
2 (0–6) 4 (1–9) 21 (1–31)
0 (0–5) 4 (1–10) 28 (20–43)
4 (0–7) 3 (1–13) 21 (7–31)
ns 5 (0–8) 6 (2–23) 1 (0–20)
*
16 (7–19) 16 (7–35) 52 (32–55)
ns 14 (7– 0) 24 (11–48) 14 (6–43)
*
15 (7–21) 16 (7–31) 36 (16–52)
Anxiety/depression No Moderate Extreme
ns 15 (6–29) 24 (10–46) 24 (17–39)
ns 15 (7–35) 17 (10–36) 30 (15–49)
ns 14 (7–33) 19 (11–41) 17 (10–53)
ns 16 (7–41) 18 (12–35) 17 (7–52)
ns 3 (0–7) 7 (1–25) 2 (1–20)
ns 4 (0–8) 3 (1–27) 14 (5–25)
ns 4 (0–7) 5 (1–20) 9 (2–36)
ns 4 (0–11) 6 (1–18) 9 (3–43)
ns 12 (6–28) 24 (11–34) 19 (11–91)
ns = Not significant. p-value < 0.05, Kruskal–Wallis test, median (interquartile range). ** p-value < 0.01, Kruskal–Wallis test, median (interquartile range). *** p-value < 0.001, Kruskal–Wallis test, median (interquartile range). a Total body surface area burned. b Total body area full-thickness burns. c Length of stay. d n = 1. e n = 2. *
18 (9–27) 43 (6–54)
12 (5–26) 23 (11–46) 11 (4–51)
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Table 3 – The ability of the EQ-5D to discriminate between clinically relevant subgroups. At work 12 months Yes
Preburn psychiatric disorder 12 months No
Yes
No
24 (67) 12 (33) 0
ns 26 (84) 5 (16) 0
26 (72) 9 (25) 1 (3)
ns 1 27 (87) 3 (19) 1 (3)
16 (44) 11 (31) 9 (25)
ns 1 19 (61) 8 (26) 4 (13)
22 (60) 10 (27) 5 (13)
6 (17) 26 (72) 4 (11)
ns 1 10 (32) 20 (64) 1 (3)
11(30) 23 (62) 3 (8)
EQ-5D dimension Mobility No Moderate Extreme Self- Care No Moderate Extreme
**
30 (94) 2 (6) 0 ***1
32 (100) 0 0 **1
Usual activities No Moderate Extreme
25 (78) 7 (22) 0
Pain No Moderate Extreme
15 (47) 17 (53) 0
Anxiety/depression No Moderate Extreme
18 (56) 13 (41) 1(3)
**1
*1
28 (76) 9 (24) 0
31 (84) 6 (16)
**1
12 (33) 20 (56) 4 (11)
8 (26) 19 (61) 4 (13)
22 (60) 14 (38) 1 (2)
x2 test, numbers (percentage), 1Fisher’s Exact Test due to small expected cell counts. ns = not significant. p-value < 0.01. ** p-value < 0.001. *** p-value < 0.05. *
Table 4 – Association between the subscales of the SF-36 and BSHS-B and the relevant EQ-5D dimensions by response level at 12 months. EQ-5D dimension
EQ-5D response level No problem
Mobility Mobility Self-care Self-care Usual activities Usual activities Pain Anxiety/depression Anxiety/depression Anxiety/depression
SF-36 subscale Physical functioning Role functioning Physical functioning Role functioning General health Social functioning Bodily pain Vitality Role emotional Mental health
Mobility Self-care Self-care Usual activities Usual activities Pain Anxiety/depression Anxiety/depression Anxiety/depression
BSHS-B subscale Simple ability Hand function Treatment regimens Simple abilities Work Heat sensitivity Affect Interpersonal relationships Sexuality
83 68 83 55 77 100 100 75 100 88
(74–100) (0–100) (65–100) (0–100) (60–92) (63–100) (84–100) (63–85) (100–100) (83–95)
4.0 4.0 3.0 4.0 3.0 2.6 3.8 4.0 4.0
(3.7–4.0) (3.6–4.0) (2.2–3.8) (3.8–4.0) (2.1–3.9) (1.6–3–6) (3.2–4.0) (3.9–4.0) (3.6–4.0)
Moderate problem 40 0 45 0 68 69 51 40 33 60
(30–58) (0–0) (33–65) (0–13) (50–76) (59–91) (41–74) (30–63) (0–67) (52–72)
3.0 2.8 2.0 4.0 1.5 1.6 2.9 3.5 3.0
(2.0–3.8) (1.2–3.6) (1.1–2.9) (3.3–4.0) (0.8–2.4) (0.6–2.6) (2.3–3.3) (3.0–4.0) (2.3–4.0)
Extreme problem – – 70 0 31 30 22 30 0 24
(70–70) (0–0) (20–64) (1–50) (15–22) (18–45) (0–17) (14–32)
– 3.8 0.8 3.0 0.0 0.3 0.7 2.3 2.0
(3.8–3.8) (0.8–0.8) (1.7–3.7) (0.0–0.8) (0.2–0.7) (0.3–1.8) (0.8–3.1) (0.7–4.0)
py <0.0001 0.004 0.001a 0.017a 0.002 <0.0001 <0.0001 0.002 <0.0001 <0.0001
<0.0001 <0.0001a 0.011a 0.001 <0.0001 0.003 <0.0001 <0.0001 0.019
Data are medians (interquartile range). Comparisons were made with different sample sizes varying from 71 to 72 (owing to missing values). y The Kruskall–Wallis test was used for comparison of distribution between groups. a The categories moderate and extreme problems were collapsed into one category for significance tests when the category extreme problems <5.
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Table 5 – Spearman rank correlations of EQ VAS and the EQ-5D index with subscales of SF-36 and BSHS-B. 6 months
12 months
EQ-5D index
EQ VAS
EQ-5D index
EQ VAS
SF-36 subscale Physical functioning Role functioning Bodily pain General health Vitality Social functioning Role emotional Mental health
0.61 0.73 0.63 0.69 0.78 0.65 0.62 0.62
0.66 0.58 0.53 0.76 0.76 0.69 0.48 0.75
0.58 0.60 0.64 0.57 0.62 0.59 0.57 0.55
0.72 0.67 0.54 0.77 0.63 0.53 0.46 0.46
BSHS-B subscale Simple abilities Heat sensitivity Hand function Treatment regimens Work Body image Affect Interpersonal relationship Sexuality
0.57 0.38 0.34 0.61 0.69 0.57 0.59 0.34 0.33
0.56 0.32 0.33 0.43 0.47 0.42 0.60 0.38 0.36
0.52 0.43 0.41 0.32 0.64 0.41 0.52 0.47 0.26*
0.54 0.41 0.51 0.37 0.45 0.44 0.53 0.50 0.48
Owing to missing values, comparisons were based on different sample sizes varying between 66 and 72. All coefficients are significantly different from zero, all other p-values < 0.01 (except p-value < 0.05). * p-value < 0.05.
0.55–0.78 (Table 5) and the correlations with the BSHS-B subscales ranged from 0.26 to 0.69. The correlation coefficients between the EQ VAS scores and the SF-36 and BSHS-B subscales ranged from 0.32 to 0.77. All coefficients were significantly different from zero.
4.
Discussion
The aim of the present study was to analyze the psychometric properties of the EQ-5D in burn-injured adults. The low proportion of missing or invalid responses for the questionnaires shows that the instrument is well understood and accepted in adults with burns, and indicates good feasibility. The EQ-5D and EQ VAS showed small floor and ceiling effects at all time points. The high proportion of individuals who perceived poor HRQoL at baseline, as indicated by an index below zero (‘‘death or worse than death’’) [45], seems to reflect that a severe burn is a devastating event that affects quality of life in all respects. The mean index values and the VAS scores improved in an expected manner between the first and last assessments. Mean values at 12 months were in line with those reported after other types of injury-related trauma [51–53], but markedly below the Swedish general population index [54]. This study suggests that rehabilitation after burn is a protracted process that continues beyond the first year after the burn, which is in line with previous long-term studies of burn-specific health [19]. Results concerning HRQoL after burns are contradictory. While some suggest that burn survivors as a group do not differ from the general population [12,13,31], others point to burn-specific physical as well as
psychological problems [11,14,15]. Our results lend support to the latter suggestion. In the present study only a small group of participants reported problems at 12 months in the dimensions mobility, self-care and usual activities, whereas almost half of them still perceived problems in the dimensions pain and anxiety/ depression. No comparable studies of EQ-5D in burn patients could be found. However, after other forms of severe trauma, researchers observed a pattern characterized by fewer problems in the anxiety/depression dimension than in our study [53,55]. A reasonable explanation for the high proportion of problems in the anxiety/depression dimension among our burn survivors may be that a group of patients afflicted by burns seems to have a psychiatric history and that such a history constitutes a risk factor for post-burn psychiatric morbidity [38,39]. Moreover, it has recently been demonstrated that the EQ-5D has the ability to identify clinical symptoms of anxiety and/or depression in a population screening [56]. As hypothesized, the EQ-5D distinguished between different levels of burn severity in an expected manner. At baseline, burn size influenced all dimensions of EQ-5D negatively except anxiety/depression, but at 12 months this effect had faded away. Longer length of stay at the Burn Unit influenced almost all dimensions negatively during the first year after burn. At 12 months, longer length of stay was still associated with more problems in the dimensions mobility and pain. This seems logical, as a longer stay in intensive care is often related to complications, which might affect long-term physical function and pain. Furthermore, the group of participants who were not working at 12 months after the burn reported significantly lower HRQoL in all dimensions as compared to those who were working. This is
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compatible with findings reported by others [11,15]. In addition, psychiatric morbidity prior to the burn was only associated with more problems in the dimension anxiety/ depression at 12 months. However, in a previous study using a disease-specific instrument, preburn psychiatric morbidity influenced perceived physical as well as psychological health negatively after the burn [38]. As generic and disease-specific measures capture somewhat different health aspects [23,24], their combined use has been recommended in the evaluation of health outcome after injury [35] and after burn [6]. Associations between the EQ-5D response levels and relevant subscale scores of the generic SF-36 and the disease-specific BSHS-B indicate that the EQ-5D has reasonable criterion validity. Furthermore, the EQ-5D index and the EQ VAS correlated well with all of the SF-36 subscales. Taken together, this may indicate that the EQ-5D reflects a construct of HRQoL that is similar to that of the SF-36. As expected, the correlations between EQ-5D and the subscales of BSHS-B were somewhat lower than for the SF-36. Sexuality and hand function showed the lowest correlations with both the EQ-5D index and the EQ VAS score which indicates that there is a satisfactory divergent validity as it has previously been shown that bad perceived health with respect to the BSHS-B subscales sexuality and hand function are relatively independent of other reported problems [19]. Limitations of the study were the relatively small sample size and that no formal reliability analysis could be done. Another possible limitation was that the three instruments cover different reference periods. Whereas EQ-5D asks about the current health state, SF-36 asks about the last 4 weeks and BSHS-B has no specific time frame. In the rehabilitation period after burn, dynamic changes in HRQoL sometimes occur over several weeks, which might have led to differences in the comparative assessments. In addition, this study was conducted on in-patients, i.e. with a certain burn severity. It can therefore not lend itself to support the use of EQ-5D in small burns that are handled as out-patients only. Furthermore, the results of this study may not apply to other geographical locations and cultural backgrounds even though the instruments are widely used in many countries around the world. Finally, the specific handling of patients during and after the injury at one particular burn unit may have an impact on the perceived HRQoL, which would further limit generalization. However, this issue cannot find an answer in the present study. Strengths of the study include repeated assessments during a period of 12 months, as well as comparisons with generic and disease-specific instruments. The prospective design with the use of a structured interview and validated burn characteristics suggest a high clinical validity.
5.
Conclusion
Overall, the EQ-5D showed good psychometric properties. The descriptive system, the EQ VAS and the EQ index are useful tools for describing aspects of HRQoL after burn injury, and for comparing outcomes with other trauma or diseases.
Further, the EQ-5D is short and easy to administer. Taken together, the results of this study support the use of the EQ-5D in burn injured adults as an adjunct to burn-specific instruments.
Conflict of interest There are no conflicts of interest to declare.
Acknowledgments This research was supported by the Swedish Research Council and the Swedish Council for Working Life and Social Research. The authors would like to thank Professor Bengt Gerdin, Department of Surgical sciences, Plastic surgery and Burn Unit, University Hospital, Uppsala University for valuable comments in previous versions of the manuscript.
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