|Costs and effectiveness of a brief MRI examination of patients with acute knee injury
|Oei EH, Nikken JJ, Ginai AZ, Krestin GP, Verhaar JA, van Vugt AB, Hunink MG
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.
This study examined the cost-effectiveness of using magnetic resonance imaging (MRI) after radiography in all or selected patients with acute knee injury. The authors concluded that the use of a short MRI examination, for selected patients whose radiograph did not show a fracture, reduced societal costs and improved the quality of life. The study was generally well conducted and satisfactorily presented. The authors’ conclusions appear to be valid.
Type of economic evaluation
This study examined the cost-effectiveness of magnetic resonance imaging (MRI) after radiography in all or selected patients with acute knee injury.
Three strategies were considered. Radiography alone was compared with radiography followed by a short MRI examination on a low-field dedicated-extremity MRI system for all patients or radiography followed by a short MRI examination for only those patients with no visible fracture on the radiograph (selective MRI).
The analysis was based on an analytic model that used data from a single study. The time horizon was six months and the authors stated that a societal perspective was adopted.
The clinical evidence came from a published prospective, pragmatic, randomised controlled trial (RCT), which was carried out at a single institution. This RCT provided evidence for radiography alone and MRI for all patients. The data for the selective MRI strategy were derived from these two options. There were 93 patients, with a mean age of 34.7 years (68% men) in the radiography group, 96 patients with a mean age of 32.2 years (62% men) in the MRI for all group, and 91 patients with a mean age of 33.7 years (63% men) from these two groups formed the selective MRI group. Patients were followed-up for six months. The key clinical endpoint was their quality of life, which was assessed using the European Quality of life (EQ-5D) questionnaire and the Short Form (SF-36) health survey.
Monetary benefit and utility valuations:
Quality of life was estimated from patients in the RCT using the EQ-5D and SF-36 at one month and at six months.
Measure of benefit:
No summary benefit measure was used. The key outcome of the clinical analysis was the change in quality of life, as reported above.
The economic analysis included both medical and non-medical costs. The former consisted of diagnostic procedures, treatment, and patient travel costs. These were estimated using official prices from the Dutch Council for Healthcare Insurance and the Dutch Central Organisation for Tariffs in Healthcare. The latter included out-of-pocket expenses and patient time costs, estimated from the Dutch Central Bureau for Statistics. Resource use data were derived directly from the RCT using specific questionnaires and supplemented with data from patient records and from the computerised hospital information system. Productivity losses were evaluated using the friction cost approach. All costs were in Euros (EUR) and the price year was 2007. The authors stated that a 3% discount rate was applied.
Analysis of uncertainty:
A series of one-way sensitivity analyses was carried out on the model inputs using arbitrary ranges of values (from 50% to 200% of the base case) to assess whether or not the cost estimates were robust. The most influential inputs were further assessed in a three-way sensitivity analysis.
After six weeks, the mean EQ-5D scores were 0.61 with radiography alone and 0.72 with selective MRI and MRI for all. The scores on the SF-36 were similar across the three strategies, but, at one and six weeks, physical functioning and physical role functioning were higher in the two MRI strategies than with radiography alone. Other endpoints (time to completion of the diagnostic work-up, duration of absence from work, and time to convalescence) were shortest with the selective MRI strategy. There was less need for additional procedures with the two MRI strategies.
The total per patient costs were EUR 2,593 (95% CI 1,815 to 3,372) with radiography alone; EUR 2,116 (95% CI 1,488 to 2,743) with MRI for all; and EUR 1,973 (95% CI 1,401 to 2,543) with selective MRI. The cost differences were mainly due to friction costs (productivity losses).
The sensitivity analysis showed that the cost estimates were sensitive to variations in friction costs (in terms of unit costs and length of friction period or time taken to replace the absent employee) and cost of the short MRI examination. The three-way sensitivity analysis showed that using plausible estimates for these three variables did not alter the results of the base-case analysis.
The authors concluded that a short MRI examination, for selected patients whose radiograph did not show a fracture, reduced societal costs and improved their quality of life.
The rationale for the selection of the three comparators was justified. The authors provided a clear description of the imaging technique and its interpretation.
The clinical evidence was derived from a well-conducted RCT and RCTs are generally considered to be valid sources of evidence due to the rigour of their design, which should minimise selection bias. Data on randomisation, the inclusion criteria, details of the flow diagram of patients passing through the study, and the assessment procedures were explicitly reported. The internal validity of the analysis was further enhanced by the use of the intention-to-diagnose-and-treat principle. A comprehensive assessment of this trial was not possible as the full methods and results were published elsewhere. The analysis was enhanced by the use of quality of life estimates taken directly from the RCT.
The analysis of costs adopted a broad perspective and all the relevant categories appear to have been included. The economic analysis was generally well conducted and reported. The methodology used to estimate the productivity losses was described. Statistical tests were appropriately used to assess the variability of the economic estimates. The price year was reported, allowing reflation exercises in other time periods. Conventional sources of data were appropriately used. The resource use data were self-reported, which might limit the analysis due to potential recall bias, but they were supplemented by data from hospital records. The unit costs and resource quantities were not presented, which limits the possibility of replicating the analysis in other settings. The authors stated that a discount rate was applied, but this appears to have been unnecessary given the short time horizon of the analysis.
Analysis and results:
The results of the analysis were clearly presented and discussed. A synthesis of the costs and benefits was not relevant given the cost-consequences framework. The issue of uncertainty was investigated using a deterministic approach and was limited to the economic data. A justification for the length of follow-up was provided and appears to have been valid. The authors noted some limitations of their analysis, such as the small number of patients included in the RCT from those eligible, and the low response rate in the quality of life questionnaires for patients in the radiography group.
The study was generally well conducted and satisfactorily presented. The authors’ conclusions appear to be valid.
Supported by the Revolving Fund of Erasmus University Medical Center Rotterdam; and Esaote S.p.A., Genoa, Italy.
Oei EH, Nikken JJ, Ginai AZ, Krestin GP, Verhaar JA, van Vugt AB, Hunink MG. Costs and effectiveness of a brief MRI examination of patients with acute knee injury. European Radiology 2009; 19(2): 409-418
Other publications of related interest
Oei EH, Nikken JJ, Ginai AZ, et al. Acute knee trauma: value of a short dedicated extremity MR imaging examination for prediction of subsequent treatment. Radiology 2005; 234: 125-133.
Nikken JJ, Oei EH, Ginai AZ, et al. Acute peripheral joint injury: cost and effectiveness of low-field-strength MR imaging-results of randomized controlled trial. Radiology 2005; 236: 958-967.
Weinstabl R, Muellner T, Vecsei V, Kainberger F, Kramer M. Economic considerations for the diagnosis and therapy of meniscal lesions: can magnetic resonance imaging help reduce the expense? World Journal of Surgery 1997; 21: 363-368.
Subject indexing assigned by NLM
Adult; Cost-Benefit Analysis; Female; Humans; Knee /pathology /radiography; Knee Injuries /diagnosis /economics /pathology /radiography; Magnetic Resonance Imaging /economics /methods; Male; Models, Theoretical; Radiography /economics /methods; Time Factors; Treatment Outcome; Wounds and Injuries /economics
Date bibliographic record published
Date abstract record published