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Cost-benefit and cost-effectiveness analysis of a disability prevention model for back pain management: a six year follow up study |
Loisel P, Lemaire J, Poitras S, Durand M-J, Champagne F, Stock S, Diallo B, Tremblay C |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology The Sherbrooke model of management for subacute occupational back pain was examined. This model combined both experimental occupational and experimental clinical rehabilitation components. The two components, occupational and clinical, were also examined independently. The occupational intervention included visits to the study occupational medicine physician and a participatory ergonomics intervention, which was limited in scope and duration, that was only intended to help the workers' rehabilitation. Job modifications were recommended to the employer who was at liberty to implement them or not.
The clinical rehabilitation intervention consisted of a clinical examination by a back pain medical specialist, participation in a back school after 8 weeks' absence from regular work and, if necessary, a multidisciplinary work rehabilitation intervention after 12 weeks' absence from work. The latter comprised a psychologist and/or occupational therapist that oversaw a progressive return to regular tasks in a programme labelled "Therapeutic Return to Work".
The interventions were discontinued after return to normal job tasks, but the ergonomic evaluation was completed even if return to work occurred before its completion. In all cases, return to regular work was authorised by the worker's treating physician who was advised by either the back pain specialist (clinical intervention group), the occupational medicine physician (occupational intervention group), or both (Sherbrooke group). The attending physicians of the workers included in the group standard care received no advice about return to work.
Type of intervention Secondary prevention and treatment.
Economic study type Cost-benefit analysis; Cost-effectiveness analysis.
Study population The study population included workers who had been absent for more than 4 weeks from their regular work due to occupational back pain.
Setting The setting was secondary care. The economic study was carried out in Quebec, Canada.
Dates to which data relate The resources, benefits and effectiveness data were collected between 1991 and 1998. The price year was 1998.
Source of effectiveness data The effectiveness data were derived from a single study.
Link between effectiveness and cost data The costing was undertaken retrospectively on the same study sample as used in the benefit and effectiveness studies.
Study sample Although not reported, it would appear that power calculations have been conducted in the planning phase of the study. Initially it was planned to recruit 200 participants, but a new policy implemented by the Quebec Workers Compensation Board led to the premature closure of recruitment. Thirty-one of the 35 workplaces agreed to participate in the study. From these a total 130 workers, who had accumulated 4 weeks of absence from regular work, were randomised to the four study groups. Fourteen of the 130 randomised workers failed to meet the inclusion criteria and 12 workers did not respond to any follow-up visit. The remaining 104 participants were distributed among the standard care group (control, n=26), clinical rehabilitation group (n=31), occupational group (n=22) and the Sherbrooke model group (n=25).
Study design This study was a randomised clinical trial. The study design included a stratified randomisation of 35 eligible workplaces according to the activity sector (manufacturing, services, health care) and the number of employees (less than or more than 500). The workplaces were randomised into two groups, one in which affected workers would undergo an occupational intervention and the other in which they would not. The eligible workers in each group were then randomised to receive the clinical rehabilitation intervention, or not, using 500 computer-generated random numbers. Each random number, along with intervention status, was placed, in order of generation, into envelopes numbered from 1 to 500. The envelopes were sealed, and the first 250 were distributed in successive order to the incoming eligible workers who were to receive the occupational intervention. The remaining 250 envelopes were distributed in successive order to incoming eligible workers who were not to receive the occupational intervention.
This cluster randomisation design was used to populate the four groups of the trial: group 1, standard care (control); group 2, experimental clinical rehabilitation intervention; group 3, experimental occupational intervention; and group 4, combination of the two experimental interventions (Sherbrooke model).
The mean follow-up period was 6.4 years (range: 5.1 - 7.5) depending on worker enrolment in the study. Twelve workers were lost to follow-up.
Analysis of effectiveness The basis of the clinical study was a per protocol analysis, as the workers that dropped out immediately after randomisation were not included. The primary health outcome used in the analysis was the number of saved days on full benefits (DFB). In each group, a mean number of equivalent DFB was calculated from the amount of income replacement and the average "per day" income replacement found in the CSST files of each worker. The dispersion measure used was an interquartile range among the first quartile (Q1) and the third quartile (Q3).
Effectiveness results In the first year, the mean number of DFB because of back pain was 126.9 (range: 25 - 188.5) in the control group, 114.9 (range: 24.4 - 204.5) in the clinical group, 116.1 (range: 26.9 - 171.3) in the occupational group, and 115.9 (range: 43.5 - 166.5) in the Sherbrooke model group.
During the total follow-up period, the mean number of DFB because of back pain was 418.3 (range: 33.1 - 313.1) in the standard care group, 178.7 (range: 24.5 - 242.5) in the clinical group, 228.0 (range: 27.3 - 200.1) in the occupational group, and 125.6 (range: 68.2 - 166.5) in the Sherbrooke model group.
All of the experimental interventions saved DFB in comparison with the standard care group. The total number of saved DFB during the total follow-up period was 239.6 for the clinical group, 190.3 for the occupational group, and 292.7 for the Sherbrooke model group.
Clinical conclusions A fully integrated disability prevention model for occupational back pain (Sherbrooke model) appears to have saved more days on benefits than usual care or partial interventions.
Measure of benefits used in the economic analysis In the CEA, the cost-effectiveness for each group was calculated by dividing the additional total costs (intervention plus consequence of disease costs) in comparison with standard care, by the number of saved DFB in comparison with standard care.
In the CBA, the cost-benefit for each experimental group of the intervention was calculated by subtracting the additional intervention costs in comparison with standard care from the saved consequence of disease costs against standard care.
Direct costs The cost/resource boundary appears to have been that of the CSST (the insurance provider). The cost data were acquired from the statistical department of the CSST that registered all eligible income replacement and health care costs associated with the work injury. For each worker, the CSST costs were compiled at the end of the intervention period (first year) and at the end of the follow-up period (31 December 1998).
The usual health care costs were for physicians, physical therapy, clinical tests, medication and devices. Income replacement costs and costs of time spent in the participatory ergonomics intervention depended on the worker's individual income. The worker's individual income was standardised to the average income of workers in the control arm (an income dependent cost was multiplied by the ratio of the mean income of the workers in the standard care arm over the individual worker's income). During the follow-up period, income replacement costs, usual health care costs, and experimental intervention costs were calculated for each worker.
All income-related costs were adjusted to 1998 Canadian dollars according to Quebec general inflation rates. All usual health care and experimental intervention costs were adjusted to 1998 Canadian dollars according to the health care inflation rates.
Statistical analysis of costs Non-parametric tests were conducted to test the statistical significance of differences in the mean costs.
Indirect Costs No indirect costs were included in the cost analysis.
Sensitivity analysis A one-way simple sensitivity analysis was performed in an attempt to test the stability of the cost-benefit results, despite variation in workers' income or health care costs that may be observed in different countries. Using data from major industrialised countries (OECD), the experimental intervention and health care costs were varied according to the total expenditure on health per capita. The income replacement costs were varied according to the mean income per capita estimated with the gross domestic product per capita, based on purchasing power parities. Sensitivity analyses were performed for the total follow-up period using the lower and upper limits of these variables.
Estimated benefits used in the economic analysis In the first year, there were 12.0 saved DFB in the clinical group, 10.8 in the occupational group and 11.0 in the Sherbrooke model group.
During the follow-up period (mean 6.4 years), there were 239.6 saved DFB in the clinical group, 190.3 in the occupational group and 292.7 in the Sherbrooke model group.
Cost results In the first year, the total intervention costs were Can$9,789 in the standard care group, Can$12,038 in the clinical group, Can$9,569 in the occupational group, and Can$12,137 in the Sherbrooke model group.
During the follow-up period (mean 6.4 years), the total intervention costs were Can$33,079 in the standard care group, Can$16,902 in the clinical group, Can$16,252 in the occupational group, and Can$14,494 in the Sherbrooke model group.
The consequences of disease costs at the one-year follow-up were Can$7,133 (range: 1,407 - 10,596) in the standard care group, Can$6,458 (range: 1,372 - 11,494) in the clinical group, Can$6,529 (range: 1,513 - 9,628) in the occupational group, and Can$6,515 (range: 2,446 - 9,359) in the Sherbrooke group.
The total consequences of disease costs at the mean 6.4 years' follow-up was Can$23,517 (range: 1,859 -17,599) in the standard care group, Can$10,045 (range: 1,376 - 13,631) in the clinical group, Can$12,820 (range: 1,532 - 11,250) in the occupational group, and Can$7,060 (range: 3,833 - 9,359) in the Sherbrooke group.
Synthesis of costs and benefits The CEA in the first year showed that the mean total costs per saved DFB, all compared with the standard care group, were Can$187.4 in the clinical group, -Can$20.4 in the occupational group, and Can$213.5 in the Sherbrooke model group. The corresponding values during the total follow-up period were -Can$67.5 in the clinical group, -Can$88.4 in the occupational group, and -Can$63.5 in the Sherbrooke model group.
The CBA showed that, compared with the standard care group, the clinical (-Can$2,250) and Sherbrooke model (-Can$2,348) groups were not cost-beneficial during the first year following the intervention, while the occupational group was moderately cost-beneficial (Can$220). Over the total follow-up period (mean 6.4 years), all experimental interventions were cost-beneficial with savings of Can$18,585 in the Sherbrooke model group, Can$16,176 in the clinical group, and Can$16,827 in the occupational group. However, the difference between groups was not statistically significant, (p=0.48; Kruskal-Wallis).
Authors' conclusions The Sherbrooke model, an innovative model of management of back pain, or its occupational or clinical/rehabilitation components might be of economic benefit for workers, compensation boards or disability insurers. The experimental interventions enabled a reduction in the time on full benefits over the long term and were not only cost-beneficial, but also very cost-effective with less total money spent to save days on benefits.
CRD COMMENTARY - Selection of comparators The choice of standard care as the comparator was justified. It represented the natural history of occupational back pain in these patients. You should decide whether it represents a valid comparator in your own setting.
Validity of estimate of measure of effectiveness The basis for the analysis of effectiveness was a population-based randomised clinical trial, which appears to have been appropriate for the study question. The study sample is likely to have been representative of the population given the selection procedure. The authors did not report any power calculations, although it was implied that they were conducted. The sample size should have been higher but, due to a policy change, ended up quite small and did not reach the number required to detect statistical significance. However, selection bias should be low since the groups were randomised using appropriate procedures. There is a possibility of confounding, as both age and gender at baseline were significantly different between the groups.
Validity of estimate of measure of benefit The estimation of benefit (number of DFB saved) was modelled. The model used to derive a measure of health benefit was clearly described.
Validity of estimate of costs The perspective of the study was that of the insurance provider and, as such, it would appear that all the relevant costs were included. The source of the cost data and detailed resource consumption data were given. In addition, the mean costs and interquartile range (Q1 - Q3) of the intervention period (first year) and the follow-up period were reported. The price year was reported and all the costs were adjusted to 1998 Canadian dollars, which should aid the reproducibility of the results. However, discounting was not conducted despite being relevant (the costs were incurred over more than 2 years).
Other issues The authors commented on some potential study biases and weaknesses, such as gender imbalance, income over prolonged disability, and problems relating to disability management associated with the choice of treatment alternatives when the study was planned. The results of the study were presented in full. The external validity of the study was improved by addressing the generalisability of the study, by specifying that disability or return-to-work are influenced by many other factors and that the results might not directly apply to other countries. The authors did not compare their results with those from other studies.
Implications of the study Work rehabilitation and workplace interventions applied to non-resolving cases of subacute occupational back pain may allow important long-term savings to workers' compensation boards and reduce the number of disability days.
Source of funding Sponsored by the Institut de Recherche en Sante et Securite au Travail du Quebec.
Bibliographic details Loisel P, Lemaire J, Poitras S, Durand M-J, Champagne F, Stock S, Diallo B, Tremblay C. Cost-benefit and cost-effectiveness analysis of a disability prevention model for back pain management: a six year follow up study. Occupational and Environmental Medicine 2002; 59(12): 807-815 Other publications of related interest Spitzer WO, LeBlanc FE, Dupuis M. Scientific approach to the assessment and management of activity-related spinal disorders. A monograph for clinicians. Report of the Quebec Task Force on Spinal Disorders. Spine 1987;12(7 Suppl):S1-59.
Loisel P, Abenhaim L, Durand P, et al. A population-based, randomized clinical trial on back pain management. Spine 1997;22:2911-8.
Frank J, Sinclair S, Hogg-Johnson S, et al. Preventing disability from work-related low-back pain. New evidence gives new hope-if we can just get all the players onside. CMAJ 1998;158:1625-31.
Elders LA, van der Beek AJ, Burdorf A. Return to work after sickness absence due to back disorders-a systematic review on intervention strategies. International Archives of Occupational and Environmental Health 2000;73:339-48.
Loisel P, Gosselin L, Durand P, et al. Implementation of a participatory ergonomics program in the rehabilitation of workers suffering from subacute back pain. Applied Ergonomics 2001;32:53-60.
Indexing Status Subject indexing assigned by NLM MeSH Absenteeism; Adult; Algorithms; Cost-Benefit Analysis /methods; Disability Evaluation; Female; Follow-Up Studies; Humans; Low Back Pain /economics /prevention & Male; Middle Aged; Occupational Diseases /economics /prevention & Occupational Health Services /economics; Sensitivity and Specificity; control; control AccessionNumber 22003000121 Date bibliographic record published 29/02/2004 Date abstract record published 29/02/2004 |
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