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The cost-effectiveness of oblique radiography in the exclusion of C7-T1 injury in trauma patients |
Kaneriya P P, Schweitzer M E, Spettell C, Cohen M J, Karasick D |
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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 Use of bilateral oblique radiography in the exclusion of C7-T1 injury in trauma patients. The intervention treatment protocol consisted of the routine three-view series (anteroposterior, lateral, and open-mouth odontoid views) complemented by bilateral oblique radiography. In this protocol, computed tomography (CT) was performed to show C7-T1 anatomy only if this region was not adequately revealed on the expanded five-view series.
Economic study type Cost-effectiveness analysis.
Study population Trauma patients presenting to the emergency department with blunt trauma.
Setting Hospital. The economic analysis was carried out in the USA.
Dates to which data relate Effectiveness and resource use data corresponded to the period from 1 January to 3 December 1994 for patients who underwent the routine three-view series complemented by CT. For those patients who underwent the routine three-view series complemented by oblique radiography effectiveness and resource use data corresponded to the period from 2 January 1996 to 31 December 1996. The price year was 1997.
Source of effectiveness data The evidence for the final outcomes was based on a single study.
Link between effectiveness and cost data Costing was performed retrospectively based on the charge data for the diagnostic procedures and on a time study of five different technologists during five separate trauma presentations.
Study sample Power calculations were not used to determine the sample size. The study sample consisted of a total of 196 patients in the CT group and 129 patients in the oblique group.
Study design This was a retrospective cohort study, carried out in a single centre. The duration of the follow-up does not appear to have been reported. The loss to follow-up was not reported. Swimmer's views were obtained when possible in both groups of patients, either at the discretion of the trauma services, or depending on clinical presentation.
Analysis of effectiveness The analysis was based on treatment completers only. The clinical outcomes were the number of cases in each group in which CT was subsequently needed to show the cervicothoracic junction, the number of cases with C7-T1 injuries, and the number of swimmer's views obtained and their outcomes. The comparability of the two study groups in terms of baseline characteristics was not investigated.
Effectiveness results The effectiveness results were as follows:
In the CT group (the first group), 50 (26%) of the 196 patients underwent CT when C7-T1 anatomy was not adequately revealed on routine three-view cervical spine radiography. In the oblique group (the second group), only 17 (13%) of the 129 patients required CT when five-view radiography failed adequately to reveal C7-T1 anatomy. This difference was statistically significant (p<0.01).
Of the 50 patients in the first group who underwent CT, six (12%) had C7-T1 injury identified on CT alone; which included 5 patients with fractures involving the C7-T1 region and one patient with C7-T1 bilateral facet joint dislocation. Of the 17 patients in the second group who underwent CT, two (11.8%) had C7-T1 injury identified on CT alone (p=0.67); both cases had fractures of the cervicothoracic junction.
Swimmer's views were obtained in 88 of the patients in the first group, seven of which showed fractures. In the second group of patients, 48 swimmer's views were obtained. Of these, five (10%) showed fractures.
Clinical conclusions The study found that the prescribed practice of performing CT on all trauma patients for whom the cervicothoracic junction was inadequately revealed resulted in a large percentage (88%) of CT scans with negative findings. The study also found that the addition of right and left oblique views to the routine three-view cervical spine series reduced by 48% the number of CT scans required to exclude C7-T1 injury.
Measure of benefits used in the economic analysis The benefit measure was completely imaged cervical spine. A blunt trauma patient's cervical spine was considered completely imaged if the skeletal anatomy was seen from the base of the occiput to the cervicothoracic junction.
Direct costs Costs were not discounted due to the short time frame of the cost analysis. The amount of technologist time was reported separately from the costs. The cost analysis covered the costs of the screening/diagnostic methods; a qualitative approximation of actual resources used was made on the basis of technologist time required to complete particular radiographic studies (time study of five different technologists during five separate trauma presentations). The perspective adopted in the cost analysis appears to have been that of the third party payer. The cost calculations were based on the Medicare reimbursement charges. The price year was 1997.
Indirect Costs Indirect costs were not considered.
Sensitivity analysis No sensitivity analysis was carried out.
Estimated benefits used in the economic analysis The number of C7-T1 anatomy shown was 146 (of 196) in the first group and 112 (of 129) in the second group, resulting in a 48% reduction in the number of CT scans required to exclude C7-T1 injury.
Cost results The total costs were not reported separately. On the basis of the Medicare reimbursement charge of $324.79 for CT of C7-T1, $49.20 for a five-view cervical spine series, and $33.43 for a three-view cervical spine series, the charges per completely imaged cervical spine are reported in the synthesis of costs and benefits below. The cost results were primarily influenced by the technologists' time. The five-view study required, on average, more than five additional minutes of a technologist's time to complete than the briefer three-view examination (10 minutes 23 seconds, range: 8 minutes 52 seconds - 11 minutes 29 seconds). The average time for a CT examination to be completed was 25 min 13 sec (range: 21 minutes 10 seconds - 29 minutes 17 seconds).
Synthesis of costs and benefits The cost per completely imaged cervical spine was $92.00 when bilateral oblique radiographs were routinely obtained, compared with $116.28 per completely imaged cervical spine when these were not obtained.
Authors' conclusions Because bilateral oblique radiography appears to be cost-effective for the exclusion of cervical spine injuries in trauma patients, the authors suggest that it be performed routinely.
CRD COMMENTARY - Selection of comparators A justification was given for the choice of the comparator. It was the standard method in the context in question at the time of the study. You, as a database user, should consider whether this is a widely used health technology in your own setting.
Validity of estimate of measure of effectiveness The internal validity of the effectiveness results cannot be guaranteed given the lack of power analysis and the fact that the retrospective nature of the study design (as acknowledged by the authors) may have resulted in biases in the analysis. The comparability of the two study groups in terms of baseline characteristics was not investigated. Furthermore, it is not entirely clear why the two samples (with a 2-year gap between them) were chosen. The degree to which the study sample was representative of the study population cannot be objectively assessed as insufficient information was provided regarding the inclusion and exclusion criteria adopted in the study.
Validity of estimate of measure of benefit The estimate of the health benefit was directly obtained from the effectiveness study. The choice of the estimate was implicitly justified. Regarding the fact that the full range of health benefits of the diagnostic modalities may not have been captured in this study, the authors did acknowledge that CT provides a more detailed evaluation of the cervical spine than radiography and that subtle injuries may be missed with bilateral oblique radiography and diagnosed with CT. However, it was stressed that the study found the incidence of injuries discovered only with CT to be similar (12% versus 11.8%) in both the three-view and five-view models.
Validity of estimate of costs The following features of the cost analysis enhanced the validity of the cost results: the quantity of the technologist time was reported separately from the costs; the price year was specified; and the perspective adopted in the cost analysis was reported. However, the following limitations may have adversely affected validity: a comprehensive cost analysis was not performed (as acknowledged by the authors); charge data were used rather than true costs; the cost analysis was retrospective; the qualitative approximation of the resources used based on technologist time may vary depending on the expertise of the particular technologist being timed (also acknowledged by the authors); statistical analysis was not performed on resource use and cost data; the effects of the two diagnostic procedures on indirect costs (productivity loss) were not addressed; the cost results may not be generalisable outside the study setting.
Other issues In view of the inherent limitations of the study design, and the lack of sensitivity analysis and statistical analysis of costs, some degree of caution should be exercised in interpreting the study results. The issue of generalisability to other settings or countries was not addressed. However, some comparisons were made with other studies. The issue of the whether the study sample was representative of the study population was not addressed. Incremental cost-effectiveness analysis was not performed despite appearing to be a necessary methodological step in the cost-effectiveness comparison of the two alternatives. The authors noted that there are many reasons for going directly to CT. Although lengthier than radiography, CT detects more fractures, better focuses on suggestive areas identified with radiography, better visualises bony fragments and vertebral canal compromise, and in particular, better detects and assesses other multi-system injury that frequently coexists with severe cervical spine trauma. One further limitation was that, although the authors attempted to justify the use of bilateral oblique radiography as an initial technique for screening trauma patients, they acknowledged that these additional views were not true screening tests because the patients were neither asymptomatic nor free of risk factors associated with cervical spine injury. In this sense, a more appropriate approach may be to consider bilateral oblique radiography as a focussed diagnostic study carried out routinely to detect and assess injury in a symptomatic population with an increased risk for developing sequelae ranging from mild neurologic deficit to complete quadriplegia. In terms of cost-effectiveness, the regular use of five-view cervical spine radiography as a focussed test instead of a screening technique is more easily justified.
Implications of the study The authors suggest that a more scientific estimate of true medical costs is required. Such cost calculations must address comprehensive labour-related costs (technician time, corrected wage indexes) in addition to numerous variables not related to labour (overhead, operating expenses, practice costs). This was beyond the scope of this study.
Bibliographic details Kaneriya P P, Schweitzer M E, Spettell C, Cohen M J, Karasick D. The cost-effectiveness of oblique radiography in the exclusion of C7-T1 injury in trauma patients. American Journal of Roentgenology 1998; 171(4): 959-962 Indexing Status Subject indexing assigned by NLM MeSH Adult; Cervical Vertebrae /injuries /radiography; Cohort Studies; Cost-Benefit Analysis; Humans; Male; Medicare /economics; Radiography /economics; Retrospective Studies; Spinal Injuries /economics /radiography; Thoracic Vertebrae /injuries /radiography; Tomography, X-Ray Computed /economics; United States AccessionNumber 21998001513 Date bibliographic record published 30/04/2001 Date abstract record published 30/04/2001 |
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