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Rapid magnetic resonance imaging for diagnosing cancer-related low back pain: a cost-effectiveness analysis |
Hollingworth W, Gray D T, Martin B I, Sullivan S D, Deyo R A, Jarvik J G |
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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 use of rapid magnetic resonance (MR) imaging for diagnosis of cancer-related low back pain (LBP).
Study population The hypothetical study population consisted of patients referred from primary care after being identified as high-risk for cancer-related back pain.
Setting The setting was secondary care. The economic study was carried out in the USA.
Dates to which data relate The effectiveness data related to studies published in 1988, 1996, 2000 and 2002. The cost data related to 2001 and 2003. The price year was 2001.
Source of effectiveness data The effectiveness data were based on a review of the literature.
Modelling A Markov model was used to translate the data on specificity and sensitivity of MR imaging and lumbar x-ray to a cost per quality-adjusted life-year (QALY). The Markov model consisted of 5 health states: (1) successfully treated cancer-related LBP, (2) persistent cancer-related LBP, (3) patient ambulant with mild paraparesis, (4) patient unable to walk, with severe paraparesis or paraplegia and (5) dead. State 3 corresponded to patients with mild spinal cord compression (SCC), while state 4 corresponded to patients with severe SCC. The model employed a cycle length of one month, and a time horizon of 3 years.
Outcomes assessed in the review The outcomes assessed in the review included the prevalence of cancer-related LBP, the sensitivity and specificity of lumbar x-ray, conventional and rapid MR imaging and biopsy, the median delay in diagnosis of cancer-related LBP, the survival of patients with cancer-related LBP, the effectiveness of treatment for cancer-related LBP and the probability of developing SCC.
Study designs and other criteria for inclusion in the review The authors did not specify the inclusion criteria for the review.
Sources searched to identify primary studies The authors did not specify the sources searched for the primary studies.
Criteria used to ensure the validity of primary studies The authors did not specify the criteria used to determine the validity of the primary studies.
Methods used to judge relevance and validity, and for extracting data The authors did not state the methods used to judge the relevance and validity of the primary studies.
Number of primary studies included The review included 9 studies as sources of effectiveness data.
Methods of combining primary studies Data from the primary studies were not synthesised.
Investigation of differences between primary studies The authors did not state whether they investigated differences between the included studies.
Results of the review The prevalence of cancer was assumed to be 1% in the base case analysis, based on author opinion with consideration of published studies.
The results of the review indicated that the sensitivity and specificity of: lumber x-ray was 0.70 and 0.95; rapid MR was 0.78 and 0.92; conventional MR was 0.93 and 0.97; and biopsy was 0.85 and 1.00, respectively. Other model input parameters identified by the review were reported in the paper.
Measure of benefits used in the economic analysis The measure of benefits in the economic analysis was QALYs. The quality weights for each health state in the model were derived from the generic Quality of Well-Being (QWB) scale, which was filled out by the authors.
Direct costs Resource use quantities were not reported separately from costs. The study included direct costs to the hospital, although some of the estimates were based on Medicare reimbursement rates as a proxy. The direct costs included the costs of the diagnostic tests and the cost of treatment. The costs of treatment were based on published provider cost-estimates, and on a previously published study. The reader is referred to 'Other Publications of Related Interest' below. Costs were discounted at an annual rate of 3%, which was justified as being the conventional rate for cost-effectiveness analyses in the US. The price year was 2001, but details of any adjustments were not provided.
Statistical analysis of costs Costs were treated in a deterministic way. This was appropriate given the lack of patient-level data.
Indirect Costs Indirect costs were not included in the analysis.
Sensitivity analysis Several univariate sensitivity analyses were undertaken to explore variability in the data. The ranges appeared to have been selected by the authors, with no explicit justification for their choice.
Estimated benefits used in the economic analysis The incremental QALYs gained with rapid MR imaging compared to lumbar x-ray were estimated to be 0.01025 per patient. Benefits were both discounted at a rate of 3% per annum. The model considered a time-horizon of 3 years, which did not go beyond the follow-up of the trial used to provide estimates of survival in patients with cancer-related LBP. The model did not consider the impact of rapid MR imaging on patients with other causes of LBP.
Cost results The cost of rapid MR imaging was estimated at $535 per patient. The cost of lumbar x-ray was estimated at $406 per patient. The model estimated these costs over a time horizon of 3 years.
Synthesis of costs and benefits Costs and benefits were combined to provide the incremental cost per QALY gained with rapid MR imaging compared to lumbar x-ray. This was estimated to be $296,176 in dollars for the year 2001, and using a discount rate of 3% per annum on costs and benefits.
Authors' conclusions The authors concluded that the current evidence did not support the use of rapid MR imaging for the diagnosis of cancer-related LBP.
CRD COMMENTARY - Selection of comparators The comparator for this analysis was chosen to represent current practice in the study setting. You should decide whether lumbar x-ray represents common practice for diagnosing cancer-related LBP in your own setting.
Validity of estimate of measure of effectiveness The authors did not state that a systematic review of the literature had been undertaken. This introduces the possibility that the evidence used in this study was not fully reflective of all the available evidence. Sources searched, study inclusion/exclusion criteria and data extraction methods were not reported. There does not appear to have been any synthesis of primary data, as single studies were selected to inform each separate model parameter. The authors did not consider the impact of differences between the primary studies when estimating effectiveness. However, they did explore each effectiveness parameter in a univariate sensitivity analysis. Given the level of detail reported it is difficult to assess if the best available evidence has been used to populate the decision model.
Validity of estimate of measure of benefit The estimate of benefits was modelled using a Markov state transition model. The preference weights were derived by the authors filling in a generic instrument, the QWB. This places greater uncertainty around the derived preference weights compared to when patients fill in such instruments.
Validity of estimate of costs The cost perspective was not explicitly reported, although it appeared to be that of the hospital. For this cost perspective adopted, all relevant categories of cost were included. Costs and quantities were not reported separately, however more detail is provided in a publication of related interest. Several univariate sensitivity analyses were conducted around the cost parameters in the model. Some Medicare reimbursement data were used to proxy costs, and the authors acknowledged that this may increase uncertainty in the results. Discounting was performed appropriately.
Other issues The authors made appropriate comparisons of their results to findings from other studies. The issue of generalisability to other settings was not addressed. The authors did not present their results selectively. The authors acknowledged that there is limited data around several of the model parameters, necessitating the use of assumptions, and increasing the uncertainty in the results. Their conclusions reflected the scope of the analysis.
Implications of the study The authors suggest that further research measuring the specificity of various rapid MR protocols in primary care populations should be prioritised.
Source of funding Supported by the Agency for Healthcare Research and Quality, grants HS09499 and HS09499 S1.
Bibliographic details Hollingworth W, Gray D T, Martin B I, Sullivan S D, Deyo R A, Jarvik J G. Rapid magnetic resonance imaging for diagnosing cancer-related low back pain: a cost-effectiveness analysis. Journal of General Internal Medicine 2003; 18(4): 303-312 Other publications of related interest Gray D T, Hollingworth W, Blackmore C C, et al. Conventional radiography, rapid MR imaging and conventional MR imaging for low back pain: activity-based costing and re-imbursement. Radiology 2003;227(3):669-680.
Indexing Status Subject indexing assigned by NLM MeSH Biopsy /economics; Cost-Benefit Analysis; Costs and Cost Analysis; Humans; Low Back Pain /diagnosis /economics /etiology; Lumbar Vertebrae /radiography; Magnetic Resonance Imaging /economics /standards; Quality of Life; Quality-Adjusted Life Years; Sensitivity and Specificity; Spinal Neoplasms /complications /economics; Survival Analysis AccessionNumber 22003000749 Date bibliographic record published 31/03/2005 Date abstract record published 31/03/2005 |
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