Comparison of WHOQOL-BREF and SF-36 in patients with HIV infection
Ping-Chuan Hsiung1, Chi-Tai Fang2,4, Yu-Yin Chang3, Mao-Yen Chen2& Jung-Der Wang2,3,4 1
School of Nursing, College of Medicine, National Taiwan University; 2Department of Internal Medicine, National Taiwan University Hospital; 3College of Public Health, National Taiwan University (E-mail: [email protected]);4Garden of Mercy Foundation, Taiwan, ROC
Accepted in revised form 8 April 2004
Abstract
The purpose of the study was to evaluate the reliability and validity of the two generic instruments, the WHOQOL and the SF-36, for assessing health-related quality of life in 224 patients with HIV infection. The internal consistency ranged from 0.75 to 0.86 across the WHOQOL-BREF domains and from 0.72 to 0.93 across the SF-36 scales. The scores of all WHOQOL-BREF domains and SF-36 scales correlated positively with the measure of happiness, Sat-HRQOL and self-perceived health status, and correlated negatively with the number and intensity of symptoms. Patients with higher CD4 cell counts scored significantly higher on G4 (general health), three WHOQOL-BREF domains, seven SF-36 scales, and PCS (physical component summary). Patients with fewer symptoms and with less intensity of symptoms had significantly higher scores on all four domains of WHOQOL-BREF, eight scales, PCS, and MCS (mental component summary) of the SF-36 scale. The correlations between the physical, psychological, and social domains of the WHOQOL-BREF and PF (physical functioning), MH (mental health), and SF (social functioning) of the SF-36 were 0.51, 0.75, and 0.54, respectively. There is also good correlation between PCS of the SF-36 and the physical domain of the WHOQOL-BREF (r¼ 0.48), and between MCS and all four domains of the WHOQOL-BREF (r range¼ 0.60–0.75). The WHOQOL-BREF domains showed fewer floor or ceiling effect than the SF-36 scales. We concluded that both the WHOQOL-BREF and the SF-36 are reliable and valid health related quality-of-life instruments in patients with HIV infection.
Key words: HIV infections, Quality of life, SF-36, WHOQOL-BREF
Introduction
Effective treatment of patients with human immunodeficiency virus (HIV) with highly active antiretroviral therapy (HAART) has decreased morbidity and mortality in these patients [1]. Since April 1997, patients with HIV infection in Taiwan have been able to receive HAART subsidized by the National Health Insurance program. With effective pharmaceutical treatment, patients are able to strive for more fulfilling and meaningful lives.
As a result, in addition to focusing on disease outcomes, the personal and social well being of patients become crucial aspects in characterizing
patient-centered outcomes. Quality of life (QOL) measures are one means to provide valuable information about patients both in clinical trials and for cost-effectiveness analysis for HIV disease [2–14]. Several QOL instruments have been applied in the evaluation of HIV-infected patients, includ-ing multiple versions of the Medical Outcome Study (MOS) [15–18], the Quality of Well-Being Scale [19], the HIV-QL31 [20], the HAT-QOL [21], the AIDS-HAQ [22], the HOPES [23], the MQoL-HIV [24], the FAHI [25], and the World Health Organization Quality of Life Instrument (WHO-QOL) [26]. Each questionnaire has its unique construct and advantages. The WHOQOL is a cross-cultural instrument developed for use across
patient groups in various countries [27] and encompasses physical, psychological, social and environment domains [28]. However, the reliability and validity of the WHOQOL have not yet been compared with other instruments in HIV-infected patients. This study aimed at comparing the reli-ability and validity of the generic WHOQOL-BREF [26, 29, 30] and the MOS Short Form-36 (SF-36) [18, 31–33], another well-established gen-eric health-related QOL instrument that has been used with success in patients with HIV infection in various Asian countries.
Methods
Subject
After our pilot study consisting a sample of 136 HIV-infected patients [26] was completed, another 224 HIV-infected patients were recruited from the outpatient clinic of Taipei Municipal Venereal Disease Control Institute (VDCI), the inpatient unit of National Taiwan University Hospital (NTUH), and a mid-way shelter run by the Gar-den of Mercy Foundation (GMF). The VDCI and NTUH provide integrated and comprehensive therapy and services for the majority of patients with HIV infection in Taiwan. GMF is the leading non-governmental Christian organization dedi-cated to the welfare of people with HIV/AIDS in Taiwan. The diagnosis of HIV infection was con-firmed by Western blot in all of the enrolled pa-tients. Informed consent was obtained for all of the participants.
Research instruments
The WHOQOL-BREF
To facilitate cross-cultural comparison in QOL research, the World Health Organization initiated an international project to develop a generic QOL instrument resulting in the final version of the 100-item WHOQOL long form. The 28-100-item WHO-QOL-BREF Taiwan version [30] used in this study was a briefly summarized version of the WHO-QOL-100. The 28 items include two general items (i.e. G1: overall QOL and G4: general health), 24 items universally adopted for WHOQOL-BREF to cover four domains (namely, physical,
psycho-logical, social, and environment), plus two na-tional items that were more specific for the culture of people of Taiwan (i.e. being respected/accepted among people, and eating what one loves to eat). The scores of the two general items range from 1 to 5, with a higher score indicating a favorable condition. The domain scores range from 4 to 20, and are calculated by multiplying the average scores for all items in the domain by 4, with a higher score indicating a better QOL on the cor-responding domain.
The SF-36
The SF-36 is a short-form health survey originally used in the MOS [31] in the United States. Sub-sequently, the International QOL Assessment (IQOLA) Project supported the feasibility of cross-cultural use of the SF-36 [34]. The SF-36 includes 36 items and covers eight scales: physical functioning (PF), role limitations due to physical health problems (RP), bodily pain (BP), general health perceptions (GH), vitality (VT), social functioning (SF), role limitations due to emotional problems (RE), and mental health (MH). All scales were linearly transformed to a 0–100 scale, with 0 indicating the least favorable status and 100 being the most favorable health status. The SF-36 also includes one item that measures health tran-sition, which was excluded from scoring in this study. Two summary measures, the physical component summary (PCS) and the mental com-ponent summary (MCS), aggregate the 8 scales. Studies showed that three scales (PF, RP, BP) contribute most to the scoring of the PCS measure, and three scales (MH, RE, SF) contribute most to the scoring of the MCS measure [35, 36]. Three of the scales (VT, GH, SF) have noteworthy corre-lations with both components. PCS and MCS were calculated using the data from the general Taiwan population [37].
The measure of happiness
The measure of happiness is a single item question using a five-point Likert scale, with a higher score indicating a favorable state.
Sat-HRQOL
Satisfaction with health-related quality of life (Sat-HRQOL) is a single item measure of overall
sat-isfaction of health-related QOL. Scores range from 0 to 100, with 0 indicating the least satisfactory and 100 being the most satisfactory health-related QOL.
Health status measures
Two health status measures were used to evaluate the validity of the selected QOL instruments. One is the self-perceived health status, a single item question using a five-point Likert scale with a higher score indicating a favorable state. The other is the revised Chinese version of the Sign and Symptom Check-List for Persons with HIV dis-ease (SSC-HIV-CR) that measures number and intensity of HIV-related symptoms. This instru-ment consists the original 28 items from the SSC-HIV-C [38, 39], plus two additional items, blurred vision and numbness, which were suggested by health care professionals experienced in providing HIV care. Item scoring for the SSC-HIV-CR ranges from 0 to 4, with 0 indicating not having the corresponding symptom, 1 indicating the least symptom intensity, and 4 being the most intensity of the symptom.
The purpose of the study was to evaluate the reliability and validity of the two generic instru-ments, the WHOQOL and the SF-36, for assessing health-related QOL in patients with HIV infection. Specifically, the authors hypothesized that if both instruments accurately captured the health-related QOL of HIV-infected patients, then: (1) the cor-responding domain/scale of both instruments should be positively correlated, i.e. the physical, psychological, and social domains of the WHO-QOL-BREF should be significantly correlated with PF, MH, and SF scales of the SF-36, respectively; (2) the physical and psychological domains of the WHOQOL-BREF should have weak associations with MCS and PCS of the SF-36, respectively; (3) the domain/scale scores of both instruments should be positively correlated with the measure of happiness, Sat-HRQOL, and self-perceived health status; (4) the domain/scale scores of both instruments should be inversely correlated with the number and intensity of symptoms; and (5) the domain/scale scores of both instruments could differentiate subjects with lower CD4 cell count, more symptoms and high intensity of symptoms from subjects with higher CD4 cell
count, fewer symptoms and low intensity of symptoms.
Statistical analysis
Data were analyzed in the following aspects: (1) descriptive statistics, (2) tests of scaling assump-tions (multitrait scaling methods), (3) reliabil-ity (Cronbach’s a for internal consistency reliability), (4) content validity (correlations be-tween item and its domain/scale and inter-domain/ scale correlations), (5) convergent and discrimi-nant validity (correlations between scores of the two instruments), (6) concurrent validity (correlations between these two instruments with other measures), and (7) known-groups validity (Student’s t test, and analysis of variance). Data were computed using SPSS for Windows, Version 10.0.
Results
Characteristics of subjects
Among the 224 enrolled patients, only one patient declined to participate. The majority of the par-ticipants were male (96.0%) with high school education or above (90.1%). Patients ranged in age from 21–75 years (mean¼ 35 years, stan-dard deviation¼ 9.14 years). Most of them (91.1%) were receiving highly active antiretrovi-ral therapy. The majority of the participants (84.4%) had CD4 cell count above 200/mm3. A high percentage (63.0%) of patients reported experiencing more than 10 symptoms. The char-acteristics of the 224 participants are summarized in Table 1.
Descriptive statistics for the WHOQOL-BREF and the SF-36
The score distributions of the WHOQOL-BREF and the SF-36 are summarized in Table 2. All of the WHOQOL-BREF domains and most of the SF-36 were negatively skewed, indicating distri-butions with more subjects scoring among the more favorable state. The full range of score dis-tributions was exhibited for PF, RP, GH, SF, RE in the SF-36. All four domains of the WHOQOL-BREF had trivial or no floor and ceiling effects.
Noteworthy flooring effects were observed for the two role-disability scales (21.9% for RP and 25% for RE) in the SF-36 indicating problems with work or other activities as a result of physical health or emotional problems. Substantial ceiling effects were observed for two scales (41.5% for PF, and 39.7% for BP) that indicate performing physical activities without limitations or with no pain. Substantial ceiling effects were also observed for the two role-disability scales (48.7% for RP, and 50.9% for RE). Modest ceiling effects were observed for one scale (18.8% for SF) that indi-cates performing social activities without interfer-ence.
Tests of scaling assumptions
Multitrait scaling techniques were used to evaluate item internal consistency and item discriminant validity (see Table 3). The range of the item internal consistency for the WHOQOL-BREF was 0.55–0.85 and 0.64–0.96 for the SF-36. A per-fect success rate, with the criteria of correlations, which equal or exceed 0.40, was observed in tests of the item internal consistency for both instru-ments. Results of item discriminant validity and scaling success rates are summarized in Table 3. A nearly perfect success rate was achieved in tests of the item discriminant validity for both instru-ments.
Reliability
The Cronbach’s a values for internal consistency ranged from 0.75 to 0.86 across the domains of the WHOQOL-BREF, and from 0.72 to 0.93 across the scales of the SF-36 (see Table 2). All of the four WHOQOL-BREF domains and all of the 8 SF-36 scales had Cronbach’s a values above 0.70, which indicates that both instruments have good reliability.
Validity
Convergent and discriminant validity. Table 4 pre-sents correlations for inter-domain/scale of the WHOQOL-BREF and the SF-36. The range of correlations for inter-domain/scale of the WHO-QOL-BREF was 0.61–0.76 (all p < 0.0001). It showed high associations among domains. All but two inter-scale correlations of the SF-36 were moderate to high associations (r range¼ 0.40– 0.72, all p < 0.0001). The exceptions were the associations between PF and MH (r¼ 0.27) and between PF and VT (r¼ 0.37). Correlations be-tween scores of the WHOQOL-BREF and the SF-36 are also shown in Table 4. The relationships of the two general items, G1 (overall QOL) and G4 (general health) of WHOQOL-BREF showed weak to moderate associations with scales of the SF-36. The highest association (r¼ 0.64) was be-tween G4 and GH of the SF-36. This implied that both measured similar concept. The weak associ-ations were between the psychological, social and environment domains of the WHOQOL-BREF
Table 1. Characteristics of 224 HIV-positive patients enrolled in this study Characteristics n = 224 (%) Age (years) 630 73 (32.6) 31–40 108 (48.2) >40 43 (19.2) Male 215 (96.0)
Education of high school or above 201 (90.1) Have been diagnosed with AIDS 63 (28.1) Current antiretroviral therapy
Nonea 20 (8.9)
PIs or NNRTIs-based regimensb 204 (91.1) Happiness Very unhappy 16 (7.1) Unhappy 48 (21.4) Moderately happy 106 (47.3) Happy 42 (18.8) Very happy 11 (4.9) Self-perceived health status
Very poor 14 (6.3)
Poor 47 (21.3)
Fair 93 (42.1)
Good 52 (23.5)
Excellent 15 (6.8) Current CD4 cell count (/mm3)
£200 35 (15.6) 201–500 93 (41.5) >500 96 (42.9) Number of symptoms None 9 (4.0) 1–10 74 (33.0) 11–20 88 (39.3) 21–30 53 (23.7)
aIncluding treatment-naive new cases and patients under
structured treatment interruption.
b
PIs: protease inhibitors; NNRTIs: non-nucleotide reverse transcriptase inhibitors.
with the PF of the SF-36 (r range¼ 0.32–0.35). The associations between the psychological and social domains of the WHOQOL-BREF with the BP of
the SF-36 (r¼ 0.33–0.39) were weak as well. The rest of the WHOQOL-BREF domains and the SF-36 scales showed a moderate to substantial
asso-Table 2. Score distributions of the WHOQOL-BREF and the SF-36 (n = 224)
Number of items
Mean ± SD 25th percentile Median 75th percentile Percent scoring at the floor Percent scoring at the ceiling Cronbach’s a WHOQOL-BREF Phy 7 13.4 ± 2.6 12.0 13.2 14.9 0.4% 0.0% 0.79 Psy 6 12.4 ± 3 10.0 12.7 14.7 0.0% 0.0% 0.85 Soc 4 12.6 ± 2.6 11.0 13.0 14.0 0.4% 0.0% 0.75 Env 9 12.7 ± 2.5 11.1 13.0 14.7 0.0% 0.0% 0.86 SF-36 PF 10 86.3 ± 19.5 80.0 95.0 100.0 0.4% 41.5% 0.93 RP 4 63.3 ± 41.4 25.0 75.0 100.0 21.9% 48.7% 0.88 BP 2 77.2 ± 22.9 62.0 80.0 100.0 0.0% 39.7% 0.89 GH 5 53 ± 23.2 35.0 52.0 72.0 0.9% 1.3% 0.83 VT 4 54 ± 19.8 40.0 55.0 70.0 0.0% 1.3% 0.82 SF 2 70.8 ± 22.4 56.3 75.0 87.5 1.3% 18.8% 0.72 RE 3 62.9 ± 42.5 16.7 100.0 100.0 25.0% 50.9% 0.85 MH 5 57.6 ± 18.9 48.0 58.0 72.0 0.0% 0.9% 0.81 PCS 49.1 ± 12.9 42.2 53.0 58.4 0.0% 0.0% MCS 43.5 ± 12.5 35.1 43.2 52.5 0.0% 0.0%
Phy = physical domain, Psy = psychological domain, Soc = social domain, Env = environment domain, PF = physical functioning, RP = role physical, BP = bodily pain, GH = general health perceptions, VT = vitality, SF = social functioning, RE = role emotional, MH = mental health, PCS = physical component summary, MCS = mental component summary.
Table 3. Tests of item internal consistency and discriminant validity of the WHOQOL-BREF and the SF-36 (n =224)
Range of Correlations Internal Consistency Testsc Discriminant Validity Testd
Item-internal consistencya
Item-discriminant validityb
#Success/total Success rate (%) #Success/total Success rate (%)
WHOQOL-BREF Physical 0.55–0.79 0.17–0.66 7/7 100 28/28 100 Psychological 0.65–0.85 0.38–0.74 6/6 100 24/24 100 Social 0.70–0.82 0.44–0.69 4/4 100 16/16 100 Environmental 0.58–0.74 0.31–0.72 9/9 100 35/36 97.2 SF-36 Physical functioning 0.64–0.86 0.09–0.55 10/10 100 80/80 100 Role physical 0.84–0.88 0.30–0.63 4/4 100 32/32 100 Bodily pain 0.95–0.96 0.35–0.69 2/2 100 16/16 100 General health perceptions 0.72–0.83 0.27–0.61 5/5 100 40/40 100 Vitality 0.75–0.86 0.13–0.64 4/4 100 32/32 100 Social functioning 0.87–0.90 0.35–0.61 2/2 100 16/16 100 Role emotional 0.85–0.90 0.34–0.68 3/3 100 24/24 100 Mental health 0.65–0.84 0.09–0.66 5/5 100 40/40 100 a
Correlation between items and hypothesized scale corrected for overlap.
b
Correlations between items and other scales.
cNumber P 0.40.
ciation (r range¼ 0.40–0.75). The highest correla-tion was found for the WHOQOL-BREF psycho-logical domain and the SF-36 MH (r¼ 0.75). The correlations between the physical, psychological, and social domains (the WHOQOL-BREF) and PF, MH, and SF (the SF-36) were 0.51, 0.75, and 0.54, respectively. This supports the first hypothesis that the corresponding domain/scale of both instruments should be positively correlated.
Regarding the two summary measures of the SF-36, the physical domain (the WHOQOL-BREF) only has moderate association with PCS (r¼ 0.48), and all four domains of the WHOQOL-BREF have strong associations with MCS (r range¼ 0.60–0.75). Strong associations were also
found between PF, RP, BP and PCS (r
range¼ 0.72–0.84) and between MH, RE, SF and MCS (range¼ 0.56–0.91). The weak associations were found between psychological, social, and environment domain of the WHOQOL and PCS of the SF-36 (r range¼ 0.26–0.32). This partially supports the second hypothesis that the physical and psychological domains (the WHOQOL-BREF) should have weak associations with MCS and PCS (the SF-36), respectively. Overall, the results of validity examination showed that both
instruments have good convergent and discrimi-nant validity.
Concurrent validity. All WHOQOL-BREF domains were substantially correlated with the measure of happiness (r range¼ 0.64–0.76), the Sat-HRQOL (r range¼ 0.66–0.70), and were moderately correlated with self-perceived health status (r range¼ 0.46–0.62, all p < 0.0001). All but one SF-36 scales were moderately to substan-tially associated with the measure of happiness (r range¼ 0.40–0.69) with the exception of PF (r¼ 0.32). All of the SF-36 scales were moderately to substantially associate with the Sat-HRQOL (r range¼ 0.40–0.63), and self-perceived health sta-tus (r range¼ 0.45–0.75, all p < 0.0001). The highest association was found between GH, the SF-36 and self-perceived health status (r¼ 0.75). PCS showed weak associations with the measure of happiness and Sat-HRQOL (r¼ 0.24, 0.39, respectively) but modest association with self-per-ceived health status (r¼ 0.46). Strong associations were evident between MCS and the measure of happiness, Sat-HRQOL, and self-perceived health status (r¼ 0.77, 0.64, 0.64, respectively). All WHOQOL-BREF domains and SF-36 scales were negatively correlated with the number of symptoms
Table 4. Correlation coefficients between WHOQOL-BREF and SF-36 (n = 224)
WHOQOL-BREF SF-36
Name G1 G4 Phy Psy Soc Env PF RP BP GH VT SF RE MH
G1 1.00 G4 0.59 1.00 Phy 0.56 0.59 1.00 Psy 0.60 0.58 0.70 1.00 Soc 0.50 0.51 0.61 0.73 1.00 Env 0.60 0.52 0.72 0.76 0.71 1.00 PF 0.15 0.24 0.51 0.32 0.35 0.33 1.00 RP 0.33 0.38 0.50 0.42 0.42 0.40 0.54 1.00 BP 0.42 0.39 0.53 0.39 0.33 0.43 0.49 0.51 1.00 GH 0.44 0.64 0.68 0.61 0.53 0.52 0.43 0.51 0.49 1.00 VT 0.51 0.59 0.68 0.68 0.54 0.61 0.37 0.51 0.45 0.68 1.00 SF 0.49 0.50 0.63 0.58 0.54 0.55 0.46 0.61 0.66 0.61 0.61 1.00 RE 0.44 0.45 0.55 0.49 0.42 0.50 0.40 0.71 0.48 0.50 0.54 0.60 1.00 MH 0.55 0.50 0.59 0.75 0.61 0.58 0.27 0.40 0.40 0.60 0.72 0.63 0.48 1.00 PCS 0.21 0.28 0.48 0.26 0.30 0.32 0.84 0.78 0.72 0.46 0.30 0.56 0.56 0.15 MCS 0.58 0.60 0.64 0.75 0.60 0.62 0.15 0.38 0.39 0.71 0.86 0.70 0.56 0.91
Phy = physical domain, Psy = psychological domain, Soc = social domain, Env = environment domain, PF = physical functioning, RP = role physical, BP = bodily pain, GH = general health perceptions, VT = vitality, SF = social functioning, RE = role emotional, MH = mental health, PCS = physical component summary, MCS = mental component summary. Note:All p value < 0.0001.
(r range¼)0.41 to )0.58, )0.46 to )0.60, respec-tively, all p < 0.0001) and intensity of symptoms (r range¼)0.44 to )0.65, )0.50 to )0.64, respec-tively, all p < 0.0001). These results support the third and the fourth hypotheses and indicate good concurrent validity of both instruments.
Known-groups validity. Table 5 shows that, in general, HIV-infected patients with higher CD4 cell counts scored significantly higher on G4 (general health), three WHOQOL-BREF domains, seven SF-36 scales, and PCS (all p < 0.05). The exceptions are G1 (overall QOL), the environment domain (the WHOQOL-BREF) and MH (the SF-36). Patients with fewer symptoms and with less intensity of symptoms had significantly higher scores on all four domains of WHOQOL-BREF, eight scales, PCS, and MCS of the SF-36 scale (all p< 0.0001, see Table 5). This supports the fifth hypothesis and indicates good known-groups validity of both instruments.
Discussion
The results of this study found that both the WHOQOL-BREF and the SF-36 had good reli-ability and validity among patients with HIV infection. The Cronbach’s a values of WHOQOL-BREF domains and SF-36 scales were generally good and comparable to results of previous studies [27–33]. Internal consistency reliability estimates for each domain/scale exceeded 0.70, supporting the usefulness of both instruments in statistical analyses involving group comparison. The nega-tively skewed score distributions of the WHOQOL-BREF and the SF-36 indicate more subjects scor-ing among the more favorable state. This is also an indication of validity, given that the majority of the subjects have high CD4 cell count and low intensity of symptoms. Noteworthy flooring and ceiling ef-fects were observed for the two role-disability scales, consistent with what have been found in previous studies [34, 40]. These two scales are the coarsest of the SF-36 scales and are more suscep-tible to floor and ceiling effects than any of the other six scales [41]. However, all domains of WHOQOL did not show any of such effects.
Correlations between the scores of correspond-ing domains/scales between the WHOQOL-BREF and SF-36 were as hypothesized. The strong asso- Ta
ble 5 . C ompariso n of the me ans fr om diffe rent do mains of WHO QOL-BREF and SF -36 for HIV patients w ith differen t severity WHO QOL-BREF SF-36 N G1 G4 Phy Psy So c Env PF RP BP GH V T SF RE MH PCS MCS CD4 coun t 6 200 35 3.0 2.7 12.1 11.0 11.8 12.0 74.2 37.1 65.5 37.0 46.7 58.6 45.7 52.6 39.9 40.0 201– 500 93 3.3 3.1 13.3 12.5 12.4 12.7 86.9 61.4 77.9 54.1 52.9 71.9 58.4 56.8 49.4 43.0 > 500 96 3.3 3.2 13.9 12.8 13.0 13.0 90.2 74.7 80.7 57.8 57.8 74.1 73.6 60.2 52.2 45.3 p valu e 0.116 6 0.011 0 0.0079 0.009 2 0.045 2 0.1572 0.001 5 < 0.0001 0.0168 < 0.000 1 0.022 2 0.0082 0.001 7 0.104 5 0.000 1 0.1016 No. of sympto ms More a 99 3.0 2.7 11.9 10.8 11.5 11.4 77.0 43.8 64.4 41.7 44.6 57.6 42.8 48.4 42.6 37.6 Less a 125 3.5 3.3 14.5 13.6 13.4 13.8 93.7 78.8 87.2 62.0 61.5 81.2 78.9 64.9 54.3 48.2 p valu e < 0.000 1 < 0.0001 < 0.000 1 < 0.000 1 < 0.0001 < 0.000 1 < 0.000 1 < 0.0001 < 0.0001 < 0.000 1 < 0.000 1 < 0.0001 < 0.000 1 < 0.000 1 < 0.0001 < 0.000 1 Inte nsity of sympto ms Hig h b 88 2.9 2.7 11.8 10.6 11.4 11.3 77.7 40.3 63.9 40.2 43.0 56.3 40.9 46.9 42.5 36.5 Low b 136 3.5 3.3 14.4 13.5 13.3 13.7 91.9 78.2 85.8 61.3 61.2 80.1 77.2 64.5 53.4 48.1 p valu e < 0.000 1 < 0.0001 < 0.000 1 < 0.000 1 < 0.0001 < 0.000 1 < 0.000 1 < 0.0001 < 0.0001 < 0.000 1 < 0.000 1 < 0.0001 < 0.000 1 < 0.000 1 < 0.0001 < 0.000 1 aCompa red with the mean value (14.35 ). bCom pared with the mean value (23.40 ).
ciations between all four domains of the WHO-QOL-BREF with MCS of the SF-36 might reflect the strong mental health component in the WHO-QOL-BREF domains. The high correlations among the four domains also direct further explo-ration of the construct of the WHOQOL-BREF. As indicated in previous studies, PF, RP, BP cor-relate most highly with PCS, and MH, RE and SF correlate highly with MCS. Correlations between SF-36 scales and the PCS and MCS support the two-dimensional model of physical and mental health [40, 42]. Although there were good correla-tions found in the scores of corresponding do-mains/scales between the WHOQOL-BREF and SF-36, there are also important differences between these two instruments. For example, items in PF of the SF-36 cover a range of clearly specified mild to vigorous physical activities in comparison with a variety of aspects (e.g. pain, energy, sleep, mobility) in the physical domain of the WHOQOL-BREF (see Appendix). Also, the content of the WHO-QOL-BREF social domain encompasses a larger scope (e.g. personal relationships, social support, sexual activity) than that of the SF-36 social func-tioning (i.e. social activities) or role funcfunc-tioning (i.e. work/daily activities) scales. As indicated in the literature, the SF-36 was originally developed as an instrument for health survey. Subsequently, it was widely used in studies of health-related QOL and MOS. Therefore, it is reasonable that the items in the SF-36 reflect more toward the scope of health status. The aim of WHOQOL-BREF was to cap-ture a broad-ranging concept of QOL to the extent of incorporating environment domain in its scope. The scores of all the WHOQOL-BREF domains and all the SF-36 scales were consistently positively correlated with the measure of happiness, Sat-HRQOL, and self-perceived health status, and negatively correlated with the number and intensity of symptoms. While the association between the PCS and the measure of happiness was found to be weak, the association between the MCS and the measure of happiness was found to be strong. It suggests that mental health component is more aligned with the concept of happiness. Further-more, there was a consistent trend of increasing scores of the WHOQOL-BREF and SF-36 along with increasing levels of CD4 lymphocyte counts. Specifically, the differential capacity of several domains/scales implies the usefulness of both
instruments in future outcome studies. Because disease-specific QOL instruments, such as the MOS-HIV [17], did not allow for cross-disease comparison, the above findings suggest that both the WHOQOL-BREF and the SF-36, although re-garded as generic health-related QOL instruments, could be quite useful for HIV-infected patients to be compared with other diseases or conditions and for cost-effectiveness and economic analysis.
Some limitations of this study should be ad-dressed. First, highly active antiretroviral therapy was freely available to all HIV-infected citizens through the Taiwan National Health Insurance program. The majority of HIV-infected patients enrolled in this study was receiving highly active antiretroviral therapy and strived to lead an active life. Thus, the results may not be directly generated to many HIV-infected patients for whom lack of accessibility to effective antiretroviral therapy is a cruel reality. Second, the majority of patients en-rolled in this study were outpatients. The study was unable to enroll a large number of inpatients because these patients were often too ill to be able to ade-quately respond to the questionnaires. Third, this study used a cross-sectional design. Future longitu-dinal studies are needed to determine the respon-siveness of these two QOL instruments to changes in the clinical status of patients with HIV infection.
In conclusion, both the WHOQOL-BREF and SF-36, two generic health-related QOL instru-ments, are useful for assessing QOL in patients with HIV infection. And, in general, there are good correlations between the corresponding do-mains/scales of the two instruments.
Acknowledgements
This study was supported by grants DOH-90-DC-1049, DOH-91-1056 from the Department of Health, Executive Yuan, Taiwan, and NHRI-EX92-9204PP from National Health Research Institutes, Taiwan. We would like to thank Dr. Shiow-Ing Wu, the Taipei Municipal Venereal Disease Control Institute, and National Taiwan University Hospital for allowing us to enroll their patients. We also thank the Garden of Mercy Foundation’s referral of subjects. We are most grateful to all the subjects of this study for their valuable participation.
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Appendix:
Correlations of item and its domain of the WHOQOL-BREF
Domains Item no. Item abbreviation Correlation
1 (G1) Overall QOL 2 (G4) General health
Physical 3 Pain and discomfort 0.61
10 Energy and fatigue 0.73
16 Sleep and rest 0.73
15 Mobility 0.72
17 Activities of daily living 0.79 4 Dependence of medical substances/aids 0.55
18 Work capacity 0.68
Psychological 5 Positive feelings 0.76 7 Thinking, learning, memory, concentration 0.76
19 Self-esteem 0.81
11 Bodily image and appearance 0.69
26 Negative feelings 0.65
6 Spirituality/religion/personal beliefs 0.85
Social 20 Personal relationships 0.82
22 Practical social support 0.78
21 Sexual activity 0.70
27 Being respected/accepted 0.72 Environment 8 Freedom, physical safety, and security 0.71
23 Home environment 0.70
12 Financial resources 0.69
24 Health and social care: accessibility and quality 0.64 13 Opportunities for acquiring new info. and skills 0.74 14 Participation in and opportunities for recreation/leisure activities 0.73 9 Physical environment (pollution/noise/traffic/climate) 0.58
25 Transport 0.72
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Address for correspondence: Jung-Der Wang, College of Public Health, National Taiwan University, Tapei 100, Taiwan Phone: +886-2-23516561; Fax: +886-2-23911308 E-mail: [email protected]
