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Keywords:

  • Rheumatoid arthritis;
  • Quality of life;
  • Validation;
  • Assessment tool

Abstract

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

Objective

To test the validity and reliability of a newly developed disease-specific multidimensional quality of life instrument: the Cedars-Sinai Health-Related Quality of Life Instrument (CSHQ-RA).

Methods

A total of 350 rheumatoid arthritis (RA) patients were asked to complete the CSHQ-RA at 2 time points (4 weeks apart). Patients also completed the Medical Outcomes Study Short Form 36 (SF-36) and the Stanford Health Assessment Questionnaire (HAQ) Disability Index (DI) at the second time point. Construct validity was tested, using Pearson's correlations, by comparing subscale scores on the CSHQ-RA to those obtained from the mental component summary (MCS) and physical component summary (PCS) of the SF-36. HAQ DI scores were used to assess the discriminant validity of the CSHQ-RA. Intraclass correlation coefficients (ICCs) were used to assess test–retest reliability.

Results

Response rates for the first and second survey were 83% (291) and 93% (276), respectively; 84% of respondents were women, and mean age was 57 years. Mean scores ± SDs on instruments were: HAQ 0.73 ± 0.69; MCS 49 ± 12; and PCS 33 ± 11. Pearson's correlations between the CSHQ-RA subscale scores and the SF-36 scores ranged from 0.55 to 0.76 (P < 0.001). Analysis of variance indicate that scores on the CSHQ-RA discriminated between levels of physical disability as measured by the HAQ (P < 0.001). Test–retest reliability was demonstrated in the instrument's subscale scores (ICC 0.70–0.90).

Conclusion

These results support the construct validity, discriminant validity, and reliability of the CSHQ-RA as a measure that captures the impact of RA on patients' health-related quality of life.


INTRODUCTION

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

We developed and initially validated the Cedars-Sinai Health-Related Quality of Life Instrument (CSHQ-RA), a multidimensional, yet disease-specific instrument for measuring health-related quality of life (HRQOL) in patients with rheumatoid arthritis (RA) (1). The instrument was intended to capture the new realities faced by RA patients, including the possibility of important improvement and potential toxicity from new drugs introduced in the 1990s. The development and subscale structure of this instrument have been previously reported, but are briefly described as follows: 1) An item pool was created from patient focus groups and a comprehensive review of published HRQOL instruments; 2) The item pool was refined by an expert panel of rheumatologists and psychometricians, and a draft questionnaire of the resulting item set was pilot tested on a group of 11 RA patients; 3) The final draft questionnaire (containing 58 items) was completed via mail by 291 (83%) of 350 patients with RA; 4) Factor analysis identified final items and subscales; and 5) Subscale convergent and discriminant validity was confirmed. The 33 items comprising the final instrument address patients' physical activity (8 items), emotional well being (8 items), dexterity (7 items), mobility (8 items), and sexual function (2 items). Each item in the CSHQ-RA asks patients to rate how RA has affected their lives during the past 4 weeks using a 5-point Likert scale. Subscale scores (i.e., sum of scores of individual items within each subscale) are transformed onto an interval scale ranging from 0 (best) to 100 (worst). The 5 subscales demonstrated internal consistency, with Cronbach's alphas ranging from 0.88 to 0.96 (2).

The present study examines the test–retest reliability, convergent and divergent validity, as well as discriminant validity (i.e., the ability to discriminate between levels of physical disability) of the CSHQ-RA.

METHODS

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

Internal review board approval was obtained from the Cedars-Sinai Health System (Los Angeles, CA) in January 2001 for survey administration.

Study design.

The study sample consisted of 350 adult, English-speaking patients with RA who were identified by their treating physicians from 13 rheumatology practices in the metropolitan Los Angeles area. The first survey mailing included the 58-item CSHQ-RA draft questionnaire, a sociodemographic and medical questionnaire, and 3 general health status questions: 1) patient's global assessment of functioning (visual analog scale [VAS]) (3); 2) patient's global assessment of joint pain (VAS); and 3) overall rating of health (item 1 from the Medical Outcomes Study Short Form 36 [SF-36]) (4). A reminder phone call was made to those who did not return the first mailing within 1 week.

After 4 weeks, patients responding to the first survey mailing were sent the CSHQ-RA draft questionnaire a second time along with the SF-36 and the Stanford Health Assessment Questionnaire (HAQ) Disability Index (DI) (5).

Other study instruments.

SF-36.

The SF-36 is a 36-item, disease-nonspecific, self-reported measure that assesses patients' HRQOL. Results from several studies of RA patients demonstrated the reliability and construct validity of the SF-36 (6–8). Two summary scales, the mental component summary (MCS) and the physical component summary (PCS) can be calculated where higher scores represent better health.

HAQ DI

The HAQ is a 20-item, self administered, arthritis-specific instrument used to assess patients' level of physical disability. The HAQ has been extensively validated in arthritis (including RA) samples (9, 10). The instrument consists of 4 sections: disability, discomfort and pain, drug side effects, and dollar costs. Only the DI was used in the present study. The 8 categories assessed by the DI are dressing and grooming, arising, eating, walking, hygiene, reaching, gripping, and common daily activities. The HAQ response scale ranges from 0 (i.e., without any difficulty) to 3 (i.e., unable to do). Two global scores are calculated from the 8 disability categories: the Standard Disability Index (disability level when controlling for aids/devices and help from others), and the Alternative Disability Index (disability level not controlling for aids/devices and help from others). Both indices yield a score ranging from 0 (no physical difficulty) to 3 (severe physical difficulty).

Validation of the CSHQ-RA.

Test–retest reliability or reproducibility was assessed using the intraclass correlation coefficient (ICC) (11). Responses to the global health question of the SF-36 (“In general, how would you say your health is?”) were used to identify participants with stable health status (i.e., whose responses did not change across baseline and 4 weeks later). ICCs were computed based on this subsample, for the 5 subscale scores at both time points. A predetermined threshold for test–retest reliability was defined as an ICC of 0.70 or greater (2, 12). Test–retest reliability was then confirmed using the approach suggested by Bland and Altman (13, 14).

Convergent and divergent validity were examined by estimating Pearson's correlation coefficient and Spearman rank-based correlation coefficient, between subscales of the CSHQ-RA and the other instruments (i.e., SF-36 and HAQ) hypothesized to assess either similar or different constructs (15, 16). We hypothesized that the scores for the subscales of the CSHQ-RA measuring aspects of physical well being (i.e., dexterity, mobility, physical activity, and sexual function) would yield a larger correlation coefficient with the PCS and the HAQ than with the MCS. Furthermore, the emotional well being subscale of the CSHQ-RA was expected to have a larger correlation coefficient with the MCS than either the PCS or HAQ. The above correlation coefficients with the PCS and the MCS were hypothesized to be negative and those with HAQ were expected to be positive.

Several studies have reported that a change of approximately 0.5 in the HAQ DI score indicates a clinically important change in health status (17, 18). Thus, to test discriminant validity, participants were divided in the present study into 6 groups of severity. For example, patients were included in the lowest severity group if their HAQ score was between 0 and 0.5 and in the highest severity group if their HAQ score was between 2.5 and 3. Mean scores on the subscales of the CSHQ-RA were compared across these 6 groups using an analyses of variance (ANOVA) and a Kruskal-Wallis test (19). Individuals with greater disability were expected to report higher CSHQ-RA scores than those with less severe disability.

Statistical analyses were performed using the Statistical Analysis System version 6.12 for Windows (SAS Institute, Cary, NC).

RESULTS

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

Sample characteristics.

Of the 291 participants who returned the initial survey, 276 (93%) completed and returned the second survey. Reasons for not participating in the study or for failing to complete the study included poor health, concerns of confidentiality, and surveys lost in the mail.

Table 1 displays the demographic and medical characteristics of the study group. The sample consisted of 248 (85%) women. Ages ranged from 20 to 92 years (mean 57 years). Regarding education, 166 participants (57%) reported obtaining at least a 2-year degree. Participants were predominantly (75%) white, non-Hispanic. Participants reported, on average, having RA for 12.7 years (± 9.9 years), with a mean score for joint pain of 45.7 (± 26.4) on a scale from 0 (no pain) to 100 (most severe pain possible).

Table 1. Sociodemographic and medical characteristics*
CharacteristicFemale n = 248 (85%)Male n = 43 (15%)Total n = 291
  • *

    RA = rheumatoid arthritis.

  • Sum not always equal to 291 due to missing data.

  • Visual analog scale score range is from 0 (no pain) to 100 (most severe pain possible).

Age, years, mean ± SD (range)57 ± 14 (20–92)59 ± 13 (25–81)57 ± 14 (20–92)
Education, n (%)   
 Grades 1 through 116 (2.4)1 (2.3)7 (2.4)
 High school42 (17.1)8 (18.6)50 (17.3)
 Some college61 (24.8)7 (16.3)68 (23.5)
 2-year college graduate36 (14.6)5 (11.6)41 (14.2)
 4-year university graduate43 (17.5)10 (23.3)53 (18.3)
 Attended or completed graduate school58 (23.6)12 (27.9)70 (24.2)
Ethnicity, n (%)   
 White, non-Hispanic184 (74.8)35 (81.4)219 (75.8)
 African American14 (5.7)3 (7.0)17 (5.9)
 Asian15 (6.1)1 (2.3)16 (5.5)
 Latino, Mexican American18 (7.3)2 (4.7)20 (6.9)
 Other15 (6.1)2 (4.7)17 (5.9)
Marital status, n (%)   
 Single, never married25 (10.1)5 (11.6)30 (10.3)
 Married137 (55.5)30 (69.8)167 (57.9)
 Separated6 (2.4)1 (2.3)7 (2.4)
 Divorced34 (13.8)1 (2.3)35 (12.1)
 Widowed38 (15.4)2 (4.7)40 (13.8)
 Living with significant other but not married7 (2.8)4 (9.3)11 (3.8)
Employment status, n (%)   
 Working for pay (full time)65 (26.5)17 (39.5)82 (28.5)
 Working for pay (part time)30 (12.2)3 (7.0)33 (11.5)
 Student (full or part time)3 (1.2)0 (0)3 (1.0)
 Full-time homemaker29 (11.8)0 (0)29 (10.1)
 Retired78 (31.8)18 (41.9)96 (33.3)
 Self employed13 (5.3)4 (9.3)17 (5.9)
 Unemployed27 (11.0)1 (2.3)28 (9.7)
Time, years, since diagnosis of RA, n (%)   
 115 (6.1)1 (2.3)16 (5.6)
 2–558 (23.7)15 (34.9)73 (25.3)
 6–1054 (22.0)11 (25.6)65 (22.6)
 11–2071 (29.0)9 (20.9)80 (27.8)
 21–3032 (13.1)6 (14.0)38 (13.2)
 31–5015 (6.1)1 (2.3)16 (5.6)
Severity of joint pain, mean ± SD (range)47 ± 26 (0–100)36 ± 27 (0–100)46 ± 26 (0–100)

Scores on the HRQOL instruments.

Means, standard deviations, medians, and interquartile ranges for all HRQOL instruments are presented in Table 2. The subscales of the CSHQ-RA with the lowest and highest mean scores were dexterity (mean ± SD; 26.1 ± 21.1) and emotional well being (52.9 ± 22.5), respectively. Mean scores on the PCS and the MCS of the SF-36 and the HAQ DI were 33.0 ± 11.0, 49.0 ± 12.0, and 0.73 ± 0.69.

Table 2. Mean, median, and interquartile ranges from the second administration (n = 276) of HRQOL instruments*
InstrumentMean ± SDMedian, IQR
  • *

    HRQOL = health-related quality of life; IQR = interquartile range; CSHQ-RA = Cedars-Sinai Health-Related Quality of Life Instrument; RA = rheumatoid arthritis; SF-36 = short form 36; HAQ = Health Assessment Questionnaire; DI = Disability Index.

  • Lower values indicate better HRQOL (CSHQ-RA) or physical well being (HAQ).

  • Mean scores are standardized from 0 to 100.

  • §

    Higher values indicate better HRQOL (SF-36).

  • Range of possible scores is 0–3.

CSHQ-RA: RA-specific quality of life  
 Dexterity26.1 ± 21.121.4, 32.1
 Mobility40.5 ± 22.240.6, 34.38
 Physical activity44.4 ± 23.943.8, 37.5
 Emotional well being52.9 ± 22.553.13, 34.4
 Sexual function43.3 ± 32.250.0, 50.0
SF-36: generic quality of life§  
 Physical component summary33.0 ± 11.030.6, 17.9
 Mental component summary49.0 ± 12.050.9, 19.9
HAQ DI: physical disability (standard)  
 Total score0.73 ± 0.690.56, 0.89

Test–retest reliability.

Of the 276 participants who completed both mailed surveys, 157 (57%) reported stable health across the 4-week test–retest time frame. Consequently, assessment of the consistency of total and subscale scores was based on 157 responders. The range of ICC for the CSHQ-RA 5 subscales was 0.78–0.90 (P ≤ 0.0001) (Table 3). Test–retest reliability was further confirmed. The differences in scores between baseline and 4 weeks for these patients on each of the 5 CSHQ-RA subscales were normally distributed. Furthermore, scatter plots of differences against the mean scores on each of the subscales provided evidence that their variability was independent of the means.

Table 3. CSHQ-RA reproducibility*
CSHQ-RANumber of itemsIntraclass correlation coefficient
  • *

    CSHQ-RA = Cedars-Sinai Health-Related Quality of Life Instrument.

Dexterity70.78
Mobility80.90
Activity80.88
Emotional well being80.86
Sexual function20.81

Construct validity.

As can be seen in Table 4, results from the analyses of convergent and divergent validity were consistent with the predicted hypotheses relative to the 4 physical functioning subscales of the CSHQ-RA. Larger Pearson's correlation coefficients were obtained with the PCS (r = −0.76) and the HAQ (r = 0.79) than with the MCS (r = −0.55). The emotional well being subscale had a greater correlation with the MCS (r = −0.51) than with the HAQ (r = 0.48). However, contrary to the a priori hypothesis, the emotional well being subscale had a slightly greater correlation with the PCS than the MCS (−0.53 versus −0.51). The above results were confirmed when using Spearman rank-based correlation coefficients (Table 4).

Table 4. Pearson's and Spearman's correlation coefficients for all HRQOL instruments*
ScaleDexterityMobilityPhysical activityEmotional well beingSexual function
  • *

    HRQOL = health-related quality of life; PCS = physical component summary; MCS = mental component summary; HAQ = Health Assessment Questionnaire.

Dexterity    
 0.69    
Mobility0.68   
Physical activity0.620.74  
 0.650.74   
Emotional well being0.510.610.69 
 0.520.610.67  
Sexual function0.420.480.600.48
 0.460.500.600.49 
PCS−0.55−0.76−0.73−0.53−0.49
 −0.58−0.78−0.72−0.51−0.49
MCS−0.35−0.38−0.56−0.51−0.36
 −0.36−0.38−0.56−0.52−0.37
HAQ0.820.780.650.480.41
 0.800.800.690.510.44

Test of known groups discriminant validity.

Results of an ANOVA performed on the 5 subscales of the CSHQ-RA are detailed in Table 5. Nearly 44% of the sample obtained a score of 0–0.5 and 4% a score of 2–3. As expected, patients who reported greater disability also reported lower quality of life (i.e., higher CSHQ-RA total scores) and vice versa. Mean scores on the 5 CSHQ-RA subscales differed significantly between groups with varying disease severity based on HAQ DI scores (P < 0.0001). These results were confirmed using a Kruskal-Wallis test (P < 0.0001).

Table 5. Known groups discriminative validity of the CSHQ-RA relative to the HAQ*
CSHQ-RA subscaleMean HAQ DI scores
0–0.5 (n = 123)0.5–1.0 (n = 70)1.0–1.5 (n = 40)1.5–2.0 (n = 23)2.0–2.5 (n = 9)2.5–3.0 (n = 5)
  • *

    P value of the analysis of variance is < 0.0001. P value of the Kruskal-Wallis test is < 0.0001. Mean scores on the CSHQ-RA are standardized from 0 to 100. CSHQ-RA = Cedars-Sinai Health-Related Quality of Life Instrument; HAQ = Health Assessment Questionnaire; DI = Disability Index.

Dexterity11.9027.2040.8349.2263.5079.29
Mobility25.1043.5356.0967.7670.7075.63
Activity29.7848.6360.0269.4675.0077.50
Emotional well being41.8257.2362.3467.5070.3175.28
Sexual function31.1446.0957.8160.7173.2175.00

DISCUSSION

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

The results from this study support the validity and reliability of the CSHQ-RA for measuring health-related quality of life in adults with RA. The subscale scores of the CSHQ-RA had high reproducibility over a 4-week test–retest timeframe (ICC 0.78–0.90). These results were expected given the inherent stability of RA over brief time periods and the fact that the sample was not part of an interventional study. The SF-36 and the HAQ DI were chosen because of their frequent utilization in RA samples, as well as their extensive validation testing on samples of RA patients. Derivatives of the HAQ have been developed, although they were found to be less discriminating and responsive (20).

The high correlations of the CSHQ-RA subscales with the HAQ and the SF-36 demonstrate the convergent validity of the instrument. As expected, subscales on the CSHQ-RA that dealt with physical disability tended to have a larger association with the HAQ and the PCS of the SF-36 than when compared with the MCS of the SF-36. Conversely, the emotional well-being scale of the CSHQ-RA had a greater association with the MCS of the SF-36 than with the HAQ. However, the correlation of the emotional well being subscale was nearly equivalent with the PCS and the MCS. One possible explanation for this finding is that emotional well being in RA may be influenced by physical well being. Alternatively, the emotional well being subscale may inadvertently capture aspects of physical well being. Further testing of the CSHQ-RA in different populations may help to clarify this issue.

Overall, results from the present investigation support the convergent and divergent validity of the subscales with tentative validity demonstrated by the emotional well being scale. Interestingly, 4 of the 5 CSHQ-RA subscales address the impact of RA on physical ability, reflecting the concerns and priorities expressed by focus group participants. The CSHQ-RA also demonstrated discriminant validity, distinguishing between individuals with different disease severity levels based on HAQ DI scores.

There are several limitations to the present study. Patient responses were based on a convenience sample from an urban section of southern California. As such, the sample was skewed toward a population with a relatively high socioeconomic status who classified themselves as non-Hispanic whites. In addition, only a few of the patients (5%) reported having severe physical disability. These characteristics might not be consistent with the general RA population. Indeed, several patients dropped out, sighting increases in their physical disability as reasons for not continuing. However, sex distribution (predominantly female) of the sample was approximately the same as the typical RA population (21).

The cross-sectional nature of the present study did not allow for testing of the CSHQ-RA's responsiveness to detect clinically important changes in health states. Additionally, we were unable to determine how much improvement in CSHQ-RA scores represents a clinically meaningful change (CMC).

Results from the present study provide evidence for the construct validity, discriminant validity, and reliability of the CSHQ-RA in the measurement of HRQOL in individuals with RA. The purpose for the development of the CSHQ-RA was to create a multidimensional instrument that contained modules that are germane to the realities of RA in the 21st century, reflecting new treatment options and potentially different outcomes from 20 years ago. Presently, the CSHQ-RA is being investigated in a phase 4, open label trial of RA patients to determine the value of a CMC, as well as to assess the instruments' responsiveness to detect changes when the patients are exposed to disease-modifying therapy expected to change their health status.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES
  • 1
    Weisman MH, Paulus HD, Russak SM, Lubeck DP, Chiou CF, Sengupta N, et al. Development of a new instrument for rheumatoid arthritis (RA): the Cedars-Sinai Health-Related Quality of Life Instrument (CSHQ-RA). Arthritis Rheum (Arthritis Care Res) 2003; 49: 7884.
  • 2
    Scientific Advisory Committee. Instrument review criteria. Medical Outcomes Trust Bulletin I-IV; 1995.
  • 3
    Huskisson EC. Measurement of pain. J Rheumatol 1982; 9: 7689.
  • 4
    Ware JE Jr, Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care 1992; 30: 47383.
  • 5
    Fries JF, Spitz P, Kraines RG, Holman HR. Measurement of patient outcome in arthritis. Arthritis Rheum 1980; 23: 13745.
  • 6
    Kosinski M, Keller SD, Hatoum HT, Kong SX, Ware JE Jr. The SF-36 health survey as a generic outcome measure in clinical trials of patients with osteoarthritis and rheumatoid arthritis: tests of data quality, scaling assumptions and score reliability. Med Care 1999; 37 Suppl: MS1022.
  • 7
    Ruta DA, Hurst NP, Kind P, Hunter M, Stubbings A. Measuring health status in British patients with rheumatoid arthritis: reliability, validity and responsiveness of the Short Form 36-item health survey (SF-36). Br J Rheumatol 1998; 37: 42536.
  • 8
    Tuttleman M, Pillemer SR, Tilley BC, Fowler SE, Buckley LM, Alarcon GS, et al, Minocycline in Rheumatoid Arthritis Trial Group. A cross sectional assessment of health status instruments in patients with rheumatoid arthritis participating in a clinical trial. J Rheumatol 1997; 24: 19105.
  • 9
    Fries JF, Spitz PW, Young DY. The dimensions of health outcomes: the health assessment questionnaire, disability and pain scales. J Rheumatol 1982; 9: 78993.
  • 10
    Bombardier C, Ware J, Russell IJ, Larson M, Chalmers A, Read JL. Auranofin therapy and quality of life in patients with rheumatoid arthritis: results of a multicenter trial. Am J Med 1986; 81: 56578.
  • 11
    Guyatt GH, Kirshner B, Jaeschke R. Measuring health status: what are the necessary measurement properties? J Clin Epidemiol 1992; 45: 13415.
  • 12
    Nunnally JC, Bernstein IH. Psychometric theory. New York: McGraw-Hill; 1994.
  • 13
    Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1: 30710.
  • 14
    Bland JM, Altman DG. Comparing two methods of clinical measurement: a personal history. Int J Epidemiol 1995; 24 Suppl 1: S7S14.
  • 15
    Campbell DT, Fiske DW. Convergent and discriminant validation by the multitrait-multidimensional matrix. Psychol Bull 2000; 56: 81105.
  • 16
    Anastasi A. Psychological testing. New York: MacMillan Publishing Company; 1990.
  • 17
    Greenwood MC, Doyle DV, Ensor M. Does the Stanford Health Assessment Questionnaire have potential as a monitoring tool for subjects with rheumatoid arthritis? Ann Rheum Dis 2001; 60: 3448.
  • 18
    Guzman J. Disability scores in DMARD trials: what is a clinically important change? [abstract] Arthritis Rheum 1996; 39 Suppl 9: S208.
  • 19
    Altman DG, Bland JM. Detecting skewness from summary information. BMJ 1996; 313: 1200.
  • 20
    Wolfe F. Which HAQ is best? A comparison of the HAQ, MHAQ and RA-HAQ, a difficult 8 item HAQ (DHAQ), and a rescored 20 item HAQ (HAQ20): analyses in 2,491 rheumatoid arthritis patients following leflunomide initiation. J Rheumatol 2001; 28: 9829.
  • 21
    Lawrence RC, Helmick CG, Arnett FC, Deyo RA, Feslon DT, Giannini EH, et al. Estimates of the prevalence of arthritis and selected musculoskeletal disorders in the United States. Arthritis Rheum 1998; 41: 77899.