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Keywords:

  • Joint replacement;
  • Quality of life;
  • Outcomes assessment

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Objective

To evaluate the psychometric properties of the World Health Organization Quality of Life short version instrument (WHOQOL-BREF), and to determine its responsiveness in assessing early outcome after total hip or knee replacement surgery.

Methods

At baseline (entry to an orthopedic waiting list), 279 participants completed the WHOQOL-BREF instrument, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Assessment of Quality of Life (AQOL) instrument, Kessler Psychological Distress (K10) scale, and the modified Health Assessment Questionnaire (MHAQ). A total of 74 patients completed reassessments 3 months after surgery.

Results

The WHOQOL-BREF demonstrated acceptable internal consistency for all domains (Cronbach's α = 0.76–0.84) and moderate concurrent validity for the physical and psychological domains (r = 0.67 for physical versus AQOL; r = −0.71 for psychological versus K10). Minimal ceiling or floor effects were identified at baseline or 3 months, except for the social relationships domain. The disease-specific WOMAC subscales were most responsive to change (relative efficiency [RE] 0.66–1.00). Apart from social relationships, all WHOQOL-BREF scores improved significantly after surgery. The physical domain was more responsive than the AQOL (RE 0.50 versus 0.42) and was similar to the MHAQ (RE 0.55 for MHAQ). The responsiveness of the psychological domain was similar to that of the K10 scale (RE 0.11 versus 0.08).

Conclusion

The WHOQOL-BREF has good psychometric properties for use in persons with severe joint disease, and by providing complementary information, it offers clinicians and researchers an additional tool for comprehensively assessing quality of life in this patient group.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

The selection of appropriate measures to assess study outcomes is an important part of planning any clinical research project and is often based on data from prior psychometric evaluations, ideally in a similar research setting. The assessment of medical intervention outcomes has moved from the traditional focus of measuring impairments to more comprehensive assessment that incorporates individuals' own perspectives and beliefs regarding their health status (1–3). Assessment of quality of life is now a major component of clinical research and has been conducted across a wide range of settings. To comprehensively assess outcome after joint replacement surgery, a combination of measures is required to produce a holistic picture of well-being. According to the World Health Organization, health is defined as “a state of complete physical, mental, and social well-being; not merely the absence of disease and infirmity” (available at www.who.int/about/definition/en). Using this definition, it is evident that although disease-specific measures such as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) can provide valuable information about physical status after surgery, additional measures are also necessary to obtain more complete information about physical, mental, and social well-being.

One measure that could provide a broader perspective in this setting is the World Health Organization Quality of Life short version instrument (WHOQOL-BREF), a generic quality of life measure that forms part of a range of instruments developed by the World Health Organization Quality of Life (WHOQOL) Group through international collaboration (4, 5). These instruments were designed to provide a cross-cultural assessment of quality of life (4) by taking into account an individual's beliefs and situation in life. Although there is some overlap between information obtained from the WHOQOL-BREF and other generic measures such as the Medical Outcomes Study 36-Item Short Form (SF-36), a unique feature of the WHOQOL-BREF is its focus on the degree of satisfaction with aspects of an individual's life. In addition to covering areas relevant to joint replacement surgery such as pain, physical function, and capacity for work, the WHOQOL-BREF also provides information not available from measures such as the SF-36. This includes dependence on medical services and environmental aspects such as the home environment, transportation, and access to health services. While the cross-cultural design of the WHOQOL-BREF is important in multicultural societies such as Australia, other features also enhance its potential applicability. The shortened format (26 questions) may be of value in clinical research where participant burden is a concern, and as with all generic quality of life measures, the WHOQOL-BREF allows for comparison across diseases, interventions, and research settings. Its availability in a range of languages (6) and readily accessible normative data (6–8) could also facilitate future international comparisons of joint replacement outcomes.

The psychometric properties of the WHOQOL-BREF have been examined in several population-based studies (6–8) and a variety of patient groups, including individuals with rheumatoid arthritis (9), spinal cord injury (10), human immunodeficiency virus (HIV) (11), and those who have undergone liver transplantation (12). However, there are no published reports of its use in patients undergoing joint replacement surgery. Given its potential as an adjunct to disease-specific tools, an evaluation of the WHOQOL-BREF's measurement properties in this setting is warranted. The purpose of this study was to assess the psychometric properties of the WHOQOL-BREF in patients undergoing total hip replacement (THR) or total knee replacement (TKR) surgery, and to determine its ability to detect change following surgery.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Participants.

This psychometric analysis forms part of a cohort study conducted at the Royal Melbourne Hospital (a large Australian public hospital) involving patients on the orthopedic waiting list for unilateral primary THR or TKR. Ethics approval was obtained from the Melbourne Health Human Research Ethics Committee. The recruitment procedure has been described elsewhere (13). Data included in this analysis were collected from December 2002 to April 2005. Patients were eligible if they were >18 years of age and able to read English and complete questionnaires. Eligible patients who provided verbal consent were mailed a consent form and baseline questionnaire. Written informed consent was obtained from all participants. If responses to questions were omitted or incomplete, direct telephone followup was undertaken. An integrated database system was developed to retrieve surgery details from the hospital database and ensure that any changes to surgery dates were promptly identified (14). A followup questionnaire was mailed 3 months after surgery.

For consistent comparison across the range of measures, only participants with complete baseline data were included in the analysis. Baseline data were available from 319 participants; of these, 279 had complete data. Mann-Whitney and chi-square tests were used to determine differences in age, sex, operation type (THR or TKR), and number of comorbidities between participants with complete baseline data (n = 279) and those with incomplete data (n = 40). There were no significant differences between these 2 groups (P > 0.05 for all tests). Of the 279 participants, 139 (50%) had not undergone surgery at the Royal Melbourne Hospital or had not reached 3 months postoperation by the end of the data collection period, 23 (8%) did not return a 3-month questionnaire, 13 (5%) were subsequently recruited into other studies and were not followed up as part of the cohort study, 13 (5%) were missed due to administrative difficulties in identifying surgery dates, 11 (4%) had incomplete 3-month data where scores could not be calculated for the full range of instruments, 4 (1%) underwent surgery other than unilateral THR or TKR and were not followed up as part of the cohort study, 1 (<1%) withdrew after baseline, 1 (<1%) died after baseline, and 74 (27%) had complete 3-month postoperative data for inclusion in the psychometric analysis.

Instruments.

WHOQOL-BREF instrument.

The Australian version of the WHOQOL-BREF instrument (7) was used. The WHOQOL-BREF contains 26 items and provides 4 domain scores (physical, psychological, social relationships, and environment) that are each scored on a 0 (poorest quality of life) to 100 (highest quality of life) scale.

WOMAC.

The WOMAC is a disease-specific measure for hip and knee osteoarthritis designed to provide a standardized assessment of self-reported health status while incorporating patient-relevant activities (15). This measure has been found to be internally consistent, with acceptable test–retest reliability and construct validity (16). The responsiveness of the WOMAC has also been evaluated in patients undergoing joint replacement surgery, with large effect sizes reported (16).

The WOMAC (Likert version 3.1) consists of 24 items (5 pain items, 2 stiffness items, and 17 physical function items). It produces 3 subscale scores (pain, stiffness, and physical function); each was transformed to a 0 (best health) to 100 (poorest health) scale for ease of interpretation.

Assessment of Quality of Life (AQOL) instrument.

The AQOL instrument was developed as a simple measure of health-related quality of life that would cover a wide range of health dimensions (17). The AQOL instrument is a multiattribute measure encompassing 4 dimensions: independent living, social relationships, physical senses, and psychological well-being (18). Its generic design allows for application across a variety of research and clinical settings, and its utility properties enable health economic evaluation (17). The AQOL instrument's psychometric properties have been evaluated in a number of settings, and normative Australian data are available for comparison (19). It was found to have good construct validity in persons with osteoarthritis and better discriminant validity than the SF-36 in this patient group (20). The AQOL instrument also demonstrated greater responsiveness than the SF-36 in a sample of elderly persons (21).

The AQOL instrument contains 12 items that are weighted to produce a utility score ranging from –0.04 (worst quality of life) to 0.00 (death equivalent) to 1.00 (full quality of life). Negative AQOL scores indicate a health state worse than death, where death is seen as preferable to the individual's current health state.

Kessler Psychological Distress scale.

Psychological distress was assessed using the Kessler Psychological Distress (K10) scale, which was developed as a screening scale for nonspecific psychological distress in the American population (22). The scale is also used in the World Health Organization World Mental Health Initiative and in Australian state and national population health surveys (23, 24). High K10 scores representing high psychological distress are strong predictors of affective disorders such as depression and anxiety (25). The scale demonstrated high internal consistency and discriminant validity in US National Health Interview Surveys (22). This instrument consists of 10 questions about anxiety, depression, and worry, and produces a total score ranging from 10 (lowest psychological distress) to 50 (highest psychological distress).

Modified Health Assessment Questionnaire.

The modified Health Assessment Questionnaire (MHAQ) is a shortened version of the Health Assessment Questionnaire (HAQ) (26) and produces an index of disability. This generic measure rates the level of difficulty that patients experience performing functional activities. Although primarily developed as measures for use in rheumatoid arthritis, the HAQ set of instruments have been used across a variety of diseases, including osteoarthritis (27, 28). The MHAQ has demonstrated high internal consistency (29) and was responsive in individuals undergoing THR (30). The MHAQ consists of 8 items covering daily activities, producing a disability index ranging from 0 (no disability) to 3 (highest disability).

Statistical analyses.

Baseline and 3-month scores were calculated according to published scoring instructions (7, 17, 25, 31, 32). Statistical analyses were performed with SPSS version 11.0 (SPSS, Chicago, IL). Baseline and demographic data from participants who completed baseline and 3-month questionnaires (n = 74) were compared with participants who had completed baseline questionnaires only (n = 205). Due to the unequal sample sizes, Mann-Whitney tests were used to compare age and baseline scores for each measure between these 2 groups. Differences in sex distribution and type of surgery (THR or TKR) were evaluated using chi-square tests.

Internal consistency was calculated for each WHOQOL-BREF domain at baseline using Cronbach's alpha. Floor and ceiling effects were compared between scales through the proportion of respondents with the poorest and best possible scores, respectively, at baseline and 3 months.

Correlation between baseline scores for each instrument was explored using Spearman's rank correlation coefficient (r). A priori hypotheses were developed regarding the strength of correlations between scales measuring similar constructs (excluding correlations between subscales or domains of the same instrument). It was hypothesized that the strongest correlations would be found between the WHOQOL-BREF physical domain and the WOMAC physical function subscale, and between the WHOQOL-BREF psychological domain and the K10 scale. Because appropriate comparators for the social relationships and environment domains of the WHOQOL-BREF could not be provided (due to their unique content), concurrent validity of these domains could not be determined.

Effect sizes were calculated by dividing the change score (difference between the mean baseline and 3-month scores) for each measure by its baseline standard deviation (33). Effect sizes were categorized into small (0.20–0.49), medium (0.50–0.79), or large (≥0.8), according to Cohen's classification (34). Paired t-tests were used to determine change from baseline to 3 months and to calculate relative efficiency (RE) (35). The t-score was squared (t2) and the instrument with the highest t2 value was used as the reference (ascribed an RE of 1.00). RE was calculated by dividing the t2 value for each measure by the t2 value of the reference.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Demographics.

Median age at baseline was 68 years (interquartile range 61–74 years). The majority of participants were women (57%) and were awaiting TKR (52%). Twenty-seven percent of participants waited <6 months for surgery, 43% waited 6–12 months, and 30% waited >12 months. At baseline, most participants were retired or receiving an age pension (71%); most were married or in a de facto relationship (63%). Sixty percent of participants were born in Australia.

The majority of participants in this study (79%) reported that they had osteoarthritis. Participants also reported other concurrent musculoskeletal conditions: 123 (44%) had back pain, 41 (15%) had osteoporosis, and 4 (1%) had fibromyalgia. Information about comorbidities was obtained using a checklist of 6 common conditions: 117 (42%) participants had hypertension, 35 (13%) had coronary artery disease, 39 (14%) had diabetes, 35 (13%) had anxiety, 34 (12%) had asthma, and 17 (6%) had cancer. A total of 110 participants (39%) had none of these specified comorbidities, 145 (52%) had 1 or 2 comorbidities, and 24 (9%) had ≥3 comorbidities. Because these conditions were self-reported, it is not known whether patients had received specific diagnosis from a medical practitioner.

Comparison of demographic and baseline data.

Demographic and baseline data for participants with complete 3-month postoperative data (n = 74), compared with participants with only baseline data (n = 205), are presented in Table 1. There was no significant difference in age, sex, or any of the baseline measures between these 2 groups. A greater proportion of individuals in the group with 3-month data, compared with the group with baseline data only, were undergoing THR (59% versus 43%; χ2 = 5.61, P = 0.02).

Table 1. Comparison of baseline and demographic data*
 Baseline and 3-month data (n = 74)Baseline data only (n = 205)P
  • *

    Values are the median (interquartile range) unless otherwise indicated. THR = total hip replacement; WHOQOL-BREF = World Health Organization Quality of Life short version instrument; WOMAC = Western Ontario and McMaster Universities Osteoarthritis Index; AQOL = Assessment of Quality of Life instrument; K10 = Kessler Psychological Distress scale; MHAQ = modified Health Assessment Questionnaire.

  • Mann-Whitney test unless otherwise indicated.

  • Chi-square test.

Age, years68 (61–75)67 (60–74)0.55
Female sex, no. (%)44 (59)116 (57)0.67
Comorbidities1 (0–1)1 (0–2)0.67
THR, no. (%)44 (59)89 (43)0.02
WHOQOL-BREF baseline   
 Physical46.4 (32.1–53.6)42.9 (32.1–57.1)0.92
 Psychological66.7 (54.2–75.0)62.5 (50.0–75.0)0.33
 Social relationships70.8 (56.3–83.3)66.7 (50.0–75.0)0.09
 Environment68.8 (56.3–75.0)65.6 (53.1–75.0)0.27
WOMAC baseline   
 Pain55.0 (43.8–66.3)60.0 (45.0–70.0)0.24
 Stiffness62.5 (50.0–75.0)62.5 (50.0–75.0)0.78
 Physical function58.8 (44.0–71.9)60.3 (47.1–72.1)0.57
AQOL baseline0.41 (0.28–0.60)0.39 (0.20–0.58)0.13
K10 baseline18.0 (14.0–21.3)18.0 (14.0–25.0)0.20
MHAQ baseline0.69 (0.38–1.13)0.71 (0.38–1.00)0.44

Baseline and 3-month postoperative data.

A summary of the baseline and 3-month postoperative scores for each measure is presented in Table 2. There were few floor effects for the WHOQOL-BREF domains (<3%) and few ceiling effects, with the exception of the social relationships domain at baseline (9%) and at 3 months (8%). Comparison with Australian normative data showed that, except for the physical domain, WHOQOL-BREF scores had reached population norms by 3 months postoperatively (Table 3).

Table 2. Summary of baseline and 3-month scores in patients undergoing joint replacement surgery*
InstrumentNo.Mean ± SDRangeFloorCeiling
  • *

    See Table 1 for definitions.

  • Percentage of patients with poorest possible score (lowest possible score for WHOQOL-BREF and AQOL; highest possible score for WOMAC, K10, and MHAQ).

  • Percentage of patients with best possible score (highest possible score for WHOQOL-BREF and AQOL; lowest possible score for WOMAC, K10, and MHAQ).

Baseline     
 WHOQOL-BREF     
  Physical27944.1 ± 18.50–96.41.10
  Psychological27961.9 ± 18.50–95.80.40
  Social relationships27964.5 ± 22.80–1002.29
  Environment27963.7 ± 16.66.3–10000.4
 WOMAC     
  Pain27957.1 ± 19.50–1002.50.4
  Stiffness27961.6 ± 21.80–1006.51.1
  Physical function27958.9 ± 20.10–1001.41.1
 AQOL2790.39 ± 0.24−0.04–0.871.80
 K1027920.3 ± 7.810–4402.2
 MHAQ2790.7 ± 0.50–2.405.4
3 months     
 WHOQOL-BREF     
  Physical7462.4 ± 16.910.7–96.400
  Psychological7470.8 ± 15.729.2–10001.4
  Social relationships7471.5 ± 18.80–1001.48.1
  Environment7471.9 ± 13.731.3–10001.4
 WOMAC     
  Pain7423.4 ± 18.20–65017.6
  Stiffness7435.0 ± 20.10–87.508.1
  Physical function7428.9 ± 17.20–64.701.4
 AQOL740.63 ± 0.210.11–0.9600
 K107416.7 ± 6.410–41012.2
 MHAQ740.3 ± 0.30–1.3014.9
Table 3. Comparison of 3-month postoperative WHOQOL-BREF scores with population norms*
WHOQOL-BREF domainOrthopedic waiting list sample (n = 74)Population (n = 396)
  • *

    Values are the mean ± SD. See Table 1 for definitions.

  • Source: Victorian Validation Study (7).

Physical62.4 ± 16.980.0 ± 17.1
Psychological70.8 ± 15.772.6 ± 14.2
Social relationships71.5 ± 18.872.2 ± 18.5
Environment71.9 ± 13.774.8 ± 13.7

Internal consistency.

All 4 WHOQOL-BREF domains demonstrated acceptable internal consistency (α = ∼0.80): α = 0.84 for physical domain, α = 0.81 for psychological domain, α = 0.76 for social relationships domain, and α = 0.80 for environment domain.

Concurrent validity.

The correlation between baseline scores for each measure is demonstrated in Table 4. The WHOQOL-BREF physical domain correlated moderately with the AQOL (r = 0.67, P < 0.01), MHAQ (r = −0.62, P < 0.01), K10 (r = −0.61, P < 0.01), WOMAC physical function (r = −0.55, P < 0.01), and WOMAC pain (r = −0.54, P < 0.01). As expected, the psychological domain correlated most strongly with the K10 (r = −0.71, P < 0.01) and showed moderate correlation with the AQOL (r = 0.50, P < 0.01). The social relationships domain did not correlate well with any of the other scales, whereas the environment domain showed moderate correlation with the K10 score only (r = −0.63, P < 0.01).

Table 4. Correlation between baseline measures in 279 patients awaiting joint replacement surgery*
 WHOQOL-BREF
PhysicalPsychologicalSocial relationshipsEnvironment
  • *

    By Spearman's rank correlation coefficient. See Table 1 for definitions.

  • P < 0.01.

  • Not significant.

  • §

    P < 0.05.

WHOQOL-BREF    
 Psychological0.57   
 Social relationships0.290.58  
 Environment0.560.700.50 
WOMAC    
 Pain−0.54−0.21−0.08−0.25
 Stiffness−0.40−0.23−0.19−0.25
 Physical function−0.55−0.25−0.13§−0.29
AQOL0.670.500.330.44
K10−0.61−0.71−0.47−0.63
MHAQ−0.62−0.37−0.26−0.36

Responsiveness to change.

The WOMAC physical function subscale had the highest RE and was used as the reference. Table 5 shows that the WHOQOL-BREF physical domain was less responsive than the disease-specific scales in detecting improvements after surgery, but was more efficient at detecting change than the generic AQOL (RE 0.50 versus 0.42). The physical domain had responsiveness similar to the MHAQ (RE 0.55). Responsiveness of the psychological domain was relatively poor and similar to that of the K10 scale (RE 0.11 versus 0.08). The responsiveness of the environment domain was comparable with that of the psychological domain (RE 0.10 versus 0.11), whereas the social relationships domain exhibited very low relative efficiency (RE 0.01).

Table 5. Responsiveness to change in 74 patients undergoing joint replacement surgery*
InstrumentMean change ± SD95% CIPEffect sizeRelative efficiency
  • *

    NS = not significant; see Table 1 for additional definitions.

  • Mean change = 3-month postoperative score minus baseline score; positive change represents improvement for WHOQOL-BREF and AQOL; negative change represents improvement for WOMAC, K10, and MHAQ.

  • Relative efficiency <1.00 indicates that the instrument is less efficient than the WOMAC physical function subscale in detecting change.

WHOQOL-BREF     
 Physical17.7 ± 18.313.4, 21.9< 0.010.980.50
 Psychological6.5 ± 14.53.1, 9.8< 0.010.420.11
 Social relationships2.6 ± 18.3−1.6, 6.8NS0.130.01
 Environment5.8 ± 13.32.7, 8.9< 0.010.430.10
WOMAC     
 Pain−31.6 ± 23.4−37.0, −26.2< 0.011.690.98
 Stiffness−26.0 ± 23.5−31.5, −20.6< 0.011.240.66
 Physical function−29.2 ± 21.4−34.1, −24.2< 0.011.451.00
AQOL0.20 ± 0.220.15, 0.25< 0.010.860.42
K10−2.4 ± 6.4−3.9, −0.9< 0.010.350.08
MHAQ−0.4 ± 0.4−0.5, −0.3< 0.010.980.55

The calculated effect sizes for each instrument (Table 5) reflect the RE findings, with large effect sizes found for the disease-specific WOMAC subscales, WHOQOL-BREF physical domain, MHAQ, and AQOL (effect sizes 0.86–1.69). Small effect sizes were found for the WHOQOL-BREF psychological and environment domains and the K10 (effect sizes 0.35–0.43). The WHOQOL-BREF social relationships domain had the lowest effect size (0.13).

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Quality of life measures such as the WHOQOL-BREF can evaluate the impact of interventions such as THR and TKR through assessment of physical, mental, and social well-being. Such measures can capture the intended and unintended effects of treatment. By focusing on an individual's perceived quality of life across a range of domains, the WHOQOL-BREF is an appropriate measure to assess these effects. Although disease-specific measures have an important role, an advantage of generic tools such as the WHOQOL-BREF is that they allow comparison between patient groups and health care interventions. Our results indicate that several psychometric properties of the WHOQOL-BREF make it a valuable adjunct for assessing quality of life in patients undergoing joint replacement surgery.

In this study, all WHOQOL-BREF domains showed good internal consistency, with values similar to or higher than those reported for persons with rheumatoid arthritis (9), spinal cord injury (10), and HIV (11). Internal consistency was also comparable with that reported by the WHOQOL Group in a large international field trial (6). The low incidence of floor effects for all WHOQOL-BREF domains at baseline was particularly encouraging, considering the known poor health of individuals awaiting joint replacement surgery (13, 36). Baseline floor effects for the WHOQOL-BREF domains were similar to or lower than those found for the WOMAC subscales. Because participants can find a comprehensive range of response options, particularly at the lower end of the WHOQOL-BREF scale, researchers and health professionals are able to obtain more precise information across the disease continuum. Minimal ceiling effects were observed for the WHOQOL-BREF postoperatively except for the social relationships domain, suggesting that despite the overwhelmingly positive effect of surgery, participants could satisfactorily rate themselves within the higher end of the scale. Our finding of higher ceiling effects for the WHOQOL-BREF social relationships domain at both time points may relate to the small number of items contributing to this score, although this was not found previously (10).

The WHOQOL-BREF demonstrated expected correlations with other questionnaires at baseline. Moderate associations were seen between the physical domain and the WOMAC pain subscale, WOMAC physical function subscale, AQOL instrument, K10, and MHAQ. The magnitudes of the correlations (r = 0.54–0.67) indicate that, although there are substantial similarities between these measures, this domain also captures different information. In this study, correlation between the physical domain and the MHAQ was similar to that reported between the physical domain and the original HAQ in persons with rheumatoid arthritis (r = −0.62 versus −0.65) (9). The relationship between this domain and the AQOL measure was also similar to that reported in an Australian population study (r = 0.67 versus 0.69) (7). The present study also demonstrates that, although there was moderate correlation between the psychological domain and the K10 scale (r = −0.71), the WHOQOL-BREF provides supplementary information. The psychological domain covers aspects not included in any of the other instruments, such as satisfaction with oneself and enjoyment of life. A similar degree of correlation was previously found between this domain and the psychological component of the Quality of Life Profile (r = 0.69) (9) and the SF-36 Mental Component Score (MCS) (r = 0.70) (7). As expected, the social relationships domain was not strongly associated with the other scales. It was not possible to provide an ideal comparative measure for this domain because it covers unique concepts such as satisfaction with personal and sexual relationships and social support. Previous clinical validation studies have also shown only small to moderate correlations between the social relationships domain and other measures (9, 11). The present study also demonstrated that, despite measuring different concepts, there was moderate correlation between the WHOQOL-BREF environment domain and the K10 scale (r = −0.63). Similar correlations were seen between the K10 and the other domains, indicating that psychological distress is associated with general dissatisfaction in many aspects of a person's life. Moderate correlations between the SF-36 MCS and each WHOQOL-BREF domain were also found in an Australian validation study (7), and similar relationships were seen between a self-evaluated happiness scale and the WHOQOL-BREF domains in individuals with HIV (11).

Although the disease-specific WOMAC showed the greatest responsiveness, the WHOQOL-BREF detected significant improvements in quality of life for the physical, psychological, and environment domains. A significant difference in social relationships was not observed; this may be due to a lack of change in relationships in the early postoperative period or to poor responsiveness of this domain. Previous studies have shown that social relationships is the least responsive domain in patients undergoing liver transplantation (12) and in patients with rheumatoid arthritis (9), although the latter study reported a larger effect size (0.31). The physical domain, which had the largest effect size of the WHOQOL-BREF domains, had an effect size greater than that calculated for the AQOL instrument and comparable with that of the MHAQ. This domain was also found to be highly responsive in persons receiving inpatient treatment for rheumatoid arthritis (9). Because the physical domain focuses on pain, physical function, and activities of daily living, it was anticipated to be efficient in detecting improvement after joint replacement. Although this domain had a responsiveness similar to the MHAQ, a major shortcoming of the MHAQ in this setting was the large number of ceiling effects at 3 months (14%). Similar findings were reported in individuals with rheumatoid arthritis (37). In this study, the efficiency of the psychological domain was similar to that of the K10 instrument. The smaller effect sizes for both measures are consistent with previous findings that physical health improves to a greater degree than psychological health after joint replacement (38, 39). A small effect size was found for the environment domain, which covers areas such as financial situation, access to health services, and transportation. These factors may only improve to a small degree after surgery, secondary to improvements in physical function and return to regular activities.

A limitation of this research is that a considerable proportion of participants could not be followed up after surgery, predominantly due to protracted waiting times (almost 3 years for some patients). Analysis of baseline and demographic data indicated that, apart from a greater proportion undergoing THR, participants who provided postoperative data were similar to those who provided baseline data only. Because preliminary analyses (data not shown) demonstrated that the WHOQOL-BREF effect sizes for the overall sample were similar to those calculated separately for THR or TKR patients, this demographic difference is unlikely to have impacted significantly on the findings. Another limitation is the focus on the early postoperative period; additional improvements may continue after this time. A 3-month assessment was used because the greatest changes in health status were expected to have occurred by this time (39, 40); our data show that WHOQOL-BREF scores were comparable with population norms for 3 of the 4 domains by this point.

This study is the first to examine the psychometric properties of the WHOQOL-BREF in a mixed sample undergoing lower-limb joint replacement. Overall, the WHOQOL-BREF has good psychometric properties, compared with disease-specific and other generic measures, in individuals with severe joint disease. While the disease-specific measures provide detailed information about pain and physical function, the WHOQOL-BREF provides complementary information and presents clinicians and researchers with an additional tool for comprehensively assessing outcomes from joint replacement surgery.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES
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