Elsevier

Applied Ergonomics

Volume 32, Issue 1, February 2001, Pages 39-46
Applied Ergonomics

The test–retest reliability of a new occupational risk factor questionnaire for outcome studies of low back pain

https://doi.org/10.1016/S0003-6870(00)00045-4Get rights and content

Abstract

This study reports the test–retest reliability of a 25-item occupational risk factor questionnaire that can be self-administered in clinical settings and used in outcome studies of low back pain or return to work programs. Subjects were 24 patients (workers on sick leave due to acute low back pain), 29 co-workers on active duty in the same jobs in a utility company, and 53 supervisors. Eighty-six subjects were re-tested within a mean interval of 7–10 days; one group of 20 supervisors was re-tested within 81 days. The questionnaire was self-administered during individual interviews. Reliability was estimated by the κ statistic as the agreement on the scores within the raters in each group. The agreement ranged from ‘slight’ (0.15) to ‘almost perfect’ (0.93) when the re-test interval was less than 43 days. Patients and non-patients were consistent in their assessment of the job demands.

Introduction

Low back pain (LBP) is the most prevalent and frequent cause of work-related functional limitations in the United States. The prevalence rates vary from 7 to 50%, depending on the definition of LBP and the data collection procedures (Behrens et al., 1994; Nordin et al., 1997). In some construction trades such as glaziers, the 12-month prevalence rates are as high as 87% (Cook et al., 1996). The total annual costs have been estimated to be over $50 billion (Nordin et al., 1997). Though common, about half of the lost work-time cases reported in the US to the Occupational Safety and Health Administration (OSHA) return to work within 6 days (BLS, 1996). The major costs are incurred by a small group of about 10% of the cases that are labeled ‘chronic’ when they remain disabled for more than 12 weeks. To prevent extended disability, treatment has begun to focus on early intervention in the acute and subacute stages of LBP (Nordin et al., 1997). Information on job demands can be used at this stage to devise functional capacity evaluations or work hardening, and to assess fitness for duty.

Mechanical (physical) and work organizational factors may be associated with the etiology and prognosis of LBP. An assessment of the occupational exposure is often obtained from job incumbents or their supervisors. Because this information has a clinical utility in early intervention, it would be of practical value to the clinician to obtain an assessment of job demands directly from the patient. Before we can use patients’ reports, it is necessary to establish whether patients in the acute phase rate their jobs similarly to alternative sources of self-reported information.

Numerous instruments are available to obtain self-reported information on the various job stressors associated with low back pain. However, very few of these are practical to administer to patients at the time of clinic visit. Spitzer et al. (1987) proposed such a questionnaire for LBP patients but it has not been validated. Moreover, an internal review of the records collected at the OIOC clinic until the end of 1995 showed poor patient compliance with this job description form. A random survey of 97 questionnaires showed that 42% of the patients completed only half of the questions. Presumably, these questions were meaningless or too complex for the respondents. Other validated or self-reported instruments have been used in ergonomic and epidemiological studies. Only one — a questionnaire developed by NIOSH1 — was reportedly used in a clinical outcomes study (Ferguson, 1998). This questionnaire has not been validated; it was also deemed too long and complex for patient use.

We set out to develop a new comprehensive questionnaire that would be easy to administer in a clinical setting, user-friendly, reliable and valid. This study reports the test–retest reliability of the risk factor questionnaire (RFQ) for patients with low back pain. Additional analyses are needed to address the validity of the instrument. The study was part of research into the factors that predict extended disability due to non-specific LBP in employees of two large companies. It addressed the need to develop and test a hazard surveillance tool that assesses job demands, which play a role in secondary prevention, and possibly in primary prevention.

Section snippets

Instrument

The RFQ collects information on a variety of categories of risk factors that may be associated with delayed recovery. It has been limited to assessing current job exposure that could be used to discover predictors of disability in the working population. An extensive literature review preceded the development of the RFQ. Three standard instruments, the AET (Rohmert and Landau, 1983), the Music study (Wiktorin et al., 1993), and the PLIBEL (Kemmlert, 1995), provided the framework for the RFQ.

Results

In total, one hundred and six subjects completed the questionnaire twice. They came from a wide variety of jobs representing a various exposures to occupational risk factors relevant to low back pain. About 28% were office workers performing technical drafting or customer service; 18% came from “heavy” jobs such as construction or warehousing. The majority of the subjects held jobs titles like drivers, mechanics, splicers, and control-room or equipment operators.

In a period of 6 weeks, thirty

Discussion

The findings of these test–retest studies raise concerns about recall bias. A short-time interval between tests is more likely to afford recall, thus explaining the better test–retest reliability of the first, third and fourth groups. Considering the low level of interest in the study, the briefness of the questionnaire, its innocuous nature, and the administration of other instruments during the initial meeting (patients and supervisors), we submit that a mean time interval of a week was

Conclusion

The test–retest reliability of the 25-item questionnaire was satisfactory when the time interval between the tests was less than 43 days. One item regarding the order and pace of tasks (4) may be ambiguous; it may be dropped from the questionnaire when administered to supervisors and employees on active duty. Patients and non-patients provided consistently reproducible responses to all items of the RFQ. To further establish the utility of the instrument, we also need to assess the inter-rater

Acknowledgements

The study was conducted with the financial support of the NIAMS (Grant RO1 AR #44288-01). Special thanks go to Anna-Lena Wendelhag-Wennerstrom who recruited the patients in this study.

References (19)

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