Reading Rheum

Metrics

Selecting an At-work Shoulder or Elbow Disability Measure

Tang K, Pitts S, Solway S, Beaton D. Comparison of the psychometric properties of four at-work disability measures in workers with shoulder or elbow disorders. J Occup Rehabil. 2009; 19:142-154.

Abstract

Introduction: To better capture the extent of work disability following an occupational injury, clinical researchers are beginning to recognize the importance of considering not only levels of absenteeism, but also disabilities experienced while “at work.” Although at-work disability measures are available in the literature, currently there is little insight on the selection of specific measures that may be best suited for a given population or situation. The objectives of this study are to assess and compare the measurement properties of four self-report at-work disability measures in workers with shoulder or elbow disorders.

Methods: Study sample consisted of 80 patients attending a shoulder and elbow specialty clinic operated by the Worker Safety Insurance Board of Ontario. Internal consistency reliability, validity, and patient preference of four at-work disability measures were compared in a cross-sectional design. Selected measures included the work module of the Disabilities of the Arm, Shoulder, and Hand Outcome Measure; Work Limitations Questionnaire (WLQ-16); Work Instability Scale for Rheumatoid Arthritis (RA-WIS); and Stanford Presenteeism Scale.

Results: All four measures demonstrated evidence of internal consistency, reliability (alpha=0.76–0.90), and construct validity, although only modest correlations against work-oriented constructs (r=0.37–0.60) were observed. The RA-WIS was most preferred by respondents (44.6%) over the other measures.

Conclusions: Although no single scale stood out as clearly superior, the WLQ-16 was considered the best overall performer. Variable performance between the scales suggests some divergence in the way these measures conceptualize “at-work disability,” which may be important to consider when selected instruments for future studies.

Commentary

Disability related to arthritis represents a major personal and economic issue for the individual and society. For the individual, the effects of pain and limited mobility affect the quality of life. More broadly, arthritis affects society through the loss of productivity. The Centers for Disease Control (CDC) report that about one in 20 U.S. adults between the ages of 18 and 64 years have work limitations due to arthritis.¹

In a previous study supported by the CDC, Theis et al used 2002 data available from the National Health Interview Survey (NHIS), to estimate the national prevalence of arthritis-attributable work limitation (AAWL) among persons between the ages of 18 and 64 years who had doctor-diagnosed arthritis. Persons were asked whether their condition affected whether they worked, the type of work they did, and the amount of work they did. Almost 30% of the 23.4 million (approximately 6.9 million) in this group reported AAWL. The site of joint pain did not seem to be a contributing factor.²

This current study by Tang et al makes a distinction between two work-related disability concepts: “absenteeism” due to disability and “at-work disability.” The authors make a case for measuring the difficulties that persons experience at work, focusing on more than just absenteeism. They believe that using complementary measures of the two concepts is important “for quantifying the impact of work-related injuries, for estimating the associated economic burden, and for evaluating the potential value and effectiveness of healthcare interventions or prevention strategies aimed at reducing this burden.”³

Four measures were selected for comparison of their psychometric properties, as well as of respondents’ preference. These measures included the following: 1) Work module of the Disabilities of the Arm, Shoulder and Hand Outcome Measure (DASH-W); 2) WLQ-16; 3) RA-WIS; and 4) Stanford Presenteeism Scale (SPS-6). The study sample was composed of 80 persons who were attending a treatment clinic for shoulder or elbow injuries. Workers referred to this clinic are typically those who experience poor recovery after their initial treatment, which may include surgery. There is no mention of the sample number who might have had an arthritis diagnosis. The average age of the sample was 43 years; 34 (42.5%) were female and 43 (53.8%) were male.

Even though the effects on work may be similar among different diagnoses, this point should be taken into consideration when looking at the study results that showed that the WLQ-16 was the “best performer” and the RA-WIS was the “most preferred.”³ Interestingly, these two measures (i.e., WLQ and RA-WIS) were reviewed in a special 2003 issue of Arthritis Care & Research that focused on measures of patient outcomes in rheumatology.⁴ Both have also been discussed as measures of productivity for persons with rheumatoid arthritis (RA).⁵

Information related to the content of these four instruments is helpful when looking at their potential use for persons with arthritis as well as understanding the study results. Below is a short description of each. All have demonstrated adequate reliability and validity prior to this study.

1. DASH-W: The DASH was designed “to measure physical function and symptoms in people with any of several musculoskeletal disorders of the upper limb.”⁶ The Work Module includes four items assessing difficulty in work performance in the past week.
2. WLQ-16: The WLQ measures “the degree to which chronic health problems interfere with the ability to perform job roles.”⁷ This measure includes 16 items, and responses are based on two-week recall. Four domains have been identified: time management, physical demands, mental–interpersonal, and output demands.
3. RA-WIS: The RA-WIS measures work instability, or the “mismatch between functional incapacity and work demands at a point in time.”⁸ It has 23 binary response (yes/no) items, with one’s response based on current perception.
4. SPS-6: The SPS-6 “assesses the relationship between presenteeism, health problems, and productivity of working populations” where “presenteeism” refers to the level of job performance due to a health problem.⁹ The initial tool of 36 items was reduced to six, and respondents are asked to rate their level of agreement with statements related to their work experiences over the past month.

Reliability, or internal consistency, was estimated for each of the four measures with this sample. All, except the RA-WIS, were analyzed using Cronbach’s coefficient alpha, appropriate for items rated on a Likert-type scale. The RA-WIS used the Kuder-Richardson technique (KR-20), appropriate for the dichotomous responses of “yes” or “no.” The reliability results ranged from .76 for the SPS-6 (six-item version) to .90 for the WLQ-16 (16 items).

To assess construct validity, correlations were used to examine the relationships of the four instruments with identified constructs expected to correlate at least moderately (>.5) or stronger (.75). Moderate correlations were projected for: 1) self-reported work productivity; 2) perceived exertion at work; and 3) perceived upper-extremity disability. Strong correlations were projected for: 1) generic work role; 2) self-rated difficulty doing work; 3) occupational performance; and 4) occupational satisfaction. The expected correlations occurred most often for the WLQ-16 and the WIS-RA; for both scales these were with self-reported work productivity and perceived upper-extremity disability. The SPS-6 met the expected correlation with self-reported work productivity. The DASH-W demonstrated no predicted correlations.

All of the tools, except the DASH-W, demonstrated known-groups validity. The groups represented current work status (i.e., normal or reduced hours). Significant results meant that those with reduced hours had greater at-work disability.

When asked which of the four tools was most preferred, 44.6% of the respondents selected the RA-WIS. It was also rated best in terms of ease of understanding, length, and making sense. The WLQ-16, though, was rated as slightly better on comprehensiveness. Even though it is not likely that this sample had many arthritis-related issues, they obviously found that they were affected by the same at-work issues. This finding suggests that disability related to arthritis is similar to that of anyone experiencing shoulder or elbow disorders.

Overall, the authors concluded that the WLQ-16 was “the best and most versatile” for measuring at-work disability in workers with shoulder or elbow disorders. This instrument demonstrated the strongest construct validity, although few of the projected correlations were strong. The WLQ-16 also showed good distributive qualities; none of the participants had a floor or ceiling score on the WLQ-16 items.

More study of these two instruments—WLQ-16 and RA-WIS—with arthritis samples needs to be done. An issue that needs to be addressed is whether the types of jobs differ for persons with different diagnoses. When the WLQ was used with patients with RA, they could not answer a number of questions.¹⁰ Patients with RA for example, may seek different types of jobs than those who have an injury-related condition or even those who have a different arthritis diagnosis. Because of the chronic nature of the disease, persons with RA may seek work that is not physically demanding. Findings of the study with patients with RA also suggest that such instruments as the Health Assessment Questionnaire (HAQ) may need to be used along with the at-work measure in order to detect functional limitations.

As a routine part of assessment in the office setting, clinicians can use a simple tool, such as the RA-WIS, in order to determine whether treatment changes or workplace adaptations need to be made. Continuing evaluation will be necessary to determine whether treatment changes are successful.⁸ Such attention to “at-work disability” can improve the personal and economic outcomes for both the individual and society.¹¹

References:

1. National Center for Disease Prevention and Health Promotion. National Arthritis Action Plan: A Public Health Strategy. Atlanta, GA: Centers for Disease Control, 2009 [Online]. Available at www.cdc.gov/nccdphp/publications/aag/pdf/arthritis.pdf. Accessed July 21, 2009.
2. Theis KA, Murphy L, Hootman JM, Helmick CG, Yelin E. Prevalence and correlates of arthritis-attributable work limitation in the US population among persons ages 18-64: 2002 National Health Interview Survey Data. Arthritis Care Res. 2007;57:355-363.
3. Tang K, Pitts S, Solway S, Beaton D. Comparison of the psychometric properties of four at-work disability measures in workers with shoulder or elbow disorders. J Occup Rehabil. 2009;19:142-154.
4. Allaire SH. Measures of adult work disability. Arthritis Care Res. 2003;49:S85-S89.
5. Hazes JMH, Geuskens GA, Burdorf A. Editorial: Work limitations in the outcome assessment of rheumatoid arthritis. J Rheumatol. 2005;32:980-982.
6. The DASH outcome measure. Available at: www.dash.iwh.on.ca/index.htm. Accessed July 24, 2009.
7. Lerner D, Amick BC, Rogers WH, Malspeis S, Bungay K, Cynn D. The work limitations questionnaire. Med Care. 2001;39:72-85.
8. Gilworth G, Chamberlain MA, Harvey A, et al. Development of a Work Instability Scale for Rheumatoid Arthritis. Arthritis Care Res. 2003;49:349-354.
9. Pelletier KR, Koopman C. Bringing health to the bottom line. Managed Healthcare Executive [online]. 2003. Available at: http://managedhealthcareexecutive.modernmedicine.com/mhe/article/articleDetail.jsp?id=134250. Accessed July 23, 2009.
10. Walker N, Michaud K, Wolfe F. Work limitations among working persons with rheumatoid arthritis: Results, reliability and validity of the Work Limitations Questionnaire in 836 patients. J Rheumatol. 2005;32:1006-1012.
11. Sokka T. Work disability in early rheumatoid arthritis. Clin Exp Rheumatol. 2003;21(5 Suppl 31):571-574.

Lupus

Head-to-head Trial of Lupus Nephritis Drugs

Appel GB, Contreras G, Dooley MA, et al. Mycophenolate mofetil versus cyclophosphamide for induction treatment of lupus nephritis. J Am Soc Nephrol. 2009; 20:1103-1112.

Abstract

Recent studies have suggested that mycophenolate mofetil (MMF) may offer advantages over intravenous cyclophosphamide (IVC) for the treatment of lupus nephritis, but these therapies have not been compared in an international randomized, controlled trial. Here, we report the comparison of MMF and IVC as induction treatment for active lupus nephritis in a multinational, two-phase (induction and maintenance) study. We randomly assigned 370 patients with classes III through V lupus nephritis to open-label MMF (target dosage 3 g/d) or IVC (0.5 to 1.0 g/m2 in monthly pulses) in a 24-week induction study. Both groups received prednisone, tapered from a maximum starting dosage of 60 mg/d. The primary end point was a prespecified decrease in urine protein/creatinine ratio and stabilization or improvement in serum creatinine. Secondary end points included complete renal remission, systemic disease activity and damage, and safety. Overall, we did not detect a significantly different response rate between the two groups: 104 (56.2%) of 185 patients responded to MMF compared with 98 (53.0%) of 185 to IVC. Secondary end points were also similar between treatment groups. There were nine deaths in the MMF group and five in the IVC group. We did not detect significant differences between the MMF and IVC groups with regard to rates of adverse events, serious adverse events, or infections. Although most patients in both treatment groups experienced clinical improvement, the study did not meet its primary objective of showing that MMF was superior to IVC as induction treatment for lupus nephritis.

Commentary

Based on promising results of small controlled trials, mycophenolate mofetil (MMF) has quickly gained popularity as an alternative to cyclophosphamide for the treatment of serious lupus nephritis. However, because the evidence was limited, questions remained about the relative efficacy and safety of these two medications. The Aspreva Lupus Management Study (ALMS) was done to help answer these questions. The initial phase of ALMS compared the efficacy and safety of MMF and monthly intravenous cyclophosphamide as induction treatment of active lupus nephritis. A subsequent phase, not yet reported, will test the relative efficacy of MMF and azathioprine as maintenance treatment.

The goal of this large controlled trial was to test if MMF was superior to monthly cyclophosphamide in controlling lupus nephritis. Three hundred seventy patients with active lupus nephritis (class III, class IV, or class V) were randomized to treatment with either MMF at a target dose of three grams daily or cyclophosphamide at a dose of 0.5 to 1.0 gram per square meter of body surface area intravenously monthly. Randomization was stratified by patient race and renal biopsy class to ensure that treatment assignments were balanced among these groups. Both treatment groups also received oral prednisone, with a prescribed taper from a maximum dose of 60 milligrams daily. The primary study endpoint was renal response at 24 weeks of treatment, defined as a decrease in urine protein/creatinine ratio by at least 50% from baseline (or to < 3 if the baseline urine protein/creatinine ratio was ≥ 3) and stabilization or improvement in serum creatinine levels from baseline. Patients and investigators were not blinded, but study endpoints were determined by a central committee that was blinded to treatment assignment. Endpoints were analyzed on an intention-to-treat basis. The study was planned to have sufficient statistical power (90%) to detect a 15% difference between groups in the proportion of patients achieving a renal response, assuming that 70% of patients would respond to MMF. The study was conducted at 88 centers in 20 countries.

Most subjects were young women who were within one year of their diagnosis of lupus nephritis. Approximately 40% were white, 33% were Asian, and 27% were of other races. Sixteen percent had class V lupus nephritis only. One hundred eighty-five patients were randomized to each treatment. The groups were well balanced in clinical and laboratory characteristics. Among those assigned to the MMF arm, the median daily dose of MMF was 2.6 grams. Among those assigned to the cyclophosphamide arm, the median dose of cyclophosphamide was 0.75 grams per square meter, and the median number of infusions was six. Eighty-one percent of patients in the MMF group completed the trial through 24 weeks, as did 84% of those in the cyclophosphamide group.

Renal response was achieved by 56% of those in the MMF group and 53% in the cyclophosphamide group. Reponses in the secondary endpoints, including complete renal remission (8.6% versus 8.1%) also did not differ between groups. In the MMF group, 35 patients withdrew from the study (21 due to adverse events), while in the cyclophosphamide group, 29 patients withdrew (12 due to adverse events). Serious adverse events occurred in 27.7% and 22.8% of patients in the MMF and cyclophosphamide groups, respectively, including nine deaths in the MMF group and five deaths in the cyclophosphamide group. Serious infections occurred in 12% and 10% of patients, respectively.

These results are notable in finding no difference in short-term efficacy, and no appreciable difference in tolerability, between MMF and intravenous cyclophosphamide as induction treatment of serious lupus nephritis. In contrast, three meta-analyses of previous smaller clinical trials indicated that MMF was more efficacious than cyclophosphamide and that MMF was safer, with a lower risk of infections, and in one meta-analysis, a lower risk of death.^1-3 Results of the meta-analyses may have been influenced by chance, publication bias, and differences among studies in the types of patients included or in the definition of endpoints. This study serves as a useful reminder that a meta-analysis of small trials is not a substitute for a large well-done trial.

However, the overall finding that both treatments were “equal” overshadows perhaps the most interesting and clinically useful finding of the study: treatment responses differed by race. The proportion of patients with a renal response was similar between treatment groups among Asians and whites. However, fewer patients of “other” races (largely blacks and mixed-ethnicity Hispanics) had a renal response to intravenous cyclophosphamide than to MMF (38.5% versus 60.4%). Previous observational studies suggested that blacks with lupus nephritis were less likely than whites to respond to treatment with cyclophosphamide, but it was unclear how much of the difference in outcomes might have been due to ethnic differences in socioeconomic conditions and access to care.^4,5 The results of ALMS suggests that the poorer responses of blacks and Hispanics to cyclophosphamide is likely not due to socioeconomic differences, and that ethnicity should be considered in treatment decisions. Based on these data, it is reasonable to consider MMF as the first choice for treatment of serious lupus nephritis in black and Hispanic patients.

The question of ethnic differences in response to cyclophosphamide deserves further investigation. Blacks treated with cyclophosphamide-based regimens in clinical trials for breast cancer or multiple myeloma did not have poorer outcomes than whites, suggesting that the association may not be generalizable to other conditions.^6,7 More importantly, ethnicity is likely only a poor surrogate for more relevant pharmacogenetic differences that influence cyclophosphamide distribution or metabolism. Understanding these differences would enable more appropriate targeting of cyclophosphamide for patients of all ethnicities, as well as for patients with conditions other than lupus nephritis that are treated with cyclophosphamide.

References

1. Moore RA, Derry S. Systematic review and meta-analysis of randomised trials and cohort studies of mycophenolate mofetil in lupus nephritis. Arthrits Res Ther. 2006; 8:R182.
2. Zhu B, Chen N, Lin Y, et al. Mycophenolate mofetil induction and maintenance therapy of severe lupus nephritis: A meta-analysis of randomized controlled trials. Nephrol Dial Transplant. 2007; 22:1933-1942.
3. Walsh M, James M, Jayne D, et al. Mycophenolate mofetil for induction therapy of lupus nephritis: A systematic review and meta-analysis. Clin J Am Soc Nephrol. 2007; 2:968-975.
4. Dooley MA, Hogan S, Jennette C, Falk R. Cyclophosphamide therapy for lupus nephritis: Poor renal survival in black Americans. Glomerular Disease Collaborative Network. Kidney Int. 1997; 51:1188-1195.
5. Contreras G, Lenz O, Pardo V, et al. Outcomes in African-Americans and Hispanics with lupus nephritis. Kidney Int. 2006; 69:1846-1851.
6. Modiano MR, Villar-Werstler P, Crowley J, Salmon SE. Evaluation of race as a prognostic factor in multiple myeloma. An ancillary of Southwest Oncology Group Study 8229. J Clin Oncol. 1996;14:974-97.
7. Roach M III, Cirrincione C, Budman D, et al. Race and survival from breast cancer: Based on Cancer and Leukemia Group B trial 8541. Cancer J Sci Am. 1997; 3:107-112.