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Potential Impact of the American College of Radiology Appropriateness Criteria on CT for Trauma

¹ Department of Radiology, Eastern Virginia Medical School, 4720 Brompton Dr., Virginia Beach, VA 23456.
² Present address: Department of Radiation Oncology, St. Vincent's Comprehensive Cancer Center, 325 W 15th St., New York, NY 10011.

Received January 10, 2005; accepted after revision February 22, 2005.

 
Address correspondence to J. L. Hadley.

Abstract

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OBJECTIVE. The purpose of our study was to identify the current imaging utilization patterns at a level 1 trauma center, the radiation dose and financial costs of this imaging, and what impact, if any, the American College of Radiology (ACR) appropriateness criteria might have on these factors.

MATERIALS AND METHODS. Two hundred trauma patients were retrospectively chosen for inclusion in the study. Patients were selected on the basis of receiving any form of ionizing radiation within the first 3 hr of arrival at an academic level 1 trauma center. Exclusion criteria included an absence of imaging, patients transferred from outside institutions with previously acquired imaging studies, and patients who first underwent surgery and subsequently returned for imaging within the 3-hr inclusion time of the study. These data were then analyzed for imaging utilization practices, estimation of radiation dose, cost, and the impact of the ACR criteria on these factors.

RESULTS. A total of 660 CT examinations were performed for a total charge of $837,028. An estimated effective dose of 16 mSv was sustained by the typical patient in the study. Overall, application of the ACR criteria was found to have the potential to reduce imaging costs by 39% and the estimated radiation dose by 44%.

CONCLUSION. The ACR appropriateness criteria have the potential to have a strong positive impact on the overall cost of imaging and radiation dose received for patients in the setting of trauma. These criteria should be emphasized to clinicians to help guide their imaging decisions.

Keywords: appropriateness criteria • CT • emergency radiology • radiation dose • trauma

Introduction

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An estimated 39 million people suffer traumatic injuries each year in the United States. Approximately 9 million of these are related to head, cervical spine, or torso injuries [1]. Nearly 41 million radiographic procedures and 8 million CT or MRI examinations were recorded for patients in U.S. emergency departments in 2002 [1]. Multiple attempts have been made over the years to develop guidelines for imaging victims of trauma that provide adequate sensitivity for injury detection and adequate cost-effectiveness. The American College of Radiology (ACR) has for several years published appropriateness criteria for many patient scenarios, including victims of trauma [2]. The purpose of this study was to identify the current utilization practices at an academic level 1 trauma center and to determine what effect, if any, adoption of the ACR criteria would have on imaging utilization. The study also sought to identify the average radiation dose and cost that trauma patients incur as a result of their imaging and the potential impact of the ACR criteria on these factors.

Materials and Methods

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The institutional review board granted a waiver of authorization for the use and disclosure of protected health information to allow data collection for this retrospective study. Two hundred trauma patients were chosen for inclusion in the study. Patients were selected on the basis of receiving any form of ionizing radiation within the first 3 hr of arrival at an academic level 1 trauma center. Patients were chosen consecutively from data recorded in the radiology department's PACS from December 2003 to February 2004. This winter time period was chosen to limit the impact of increased imaging utilization that is seen with the arrival of new residents in the summer months. A total of 140 men and 60 women met the inclusion criteria. Patient ages, excluding fetuses, ranged from 2 months to 83 years (mean age, 36 ± 15 [SD] years). Seventy-six patients (25 female, 51 male) were younger than 30 years at the time of imaging. Patients were excluded who did not undergo imaging, who transferred from outside institutions with previously acquired imaging studies, and who first underwent surgery and subsequently returned for imaging within the 3-hr inclusion time of the study.

View larger version (21K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1 —Bar graph shows total number of patients distributed by mechanism of injury. MVC = motor vehicle collision, GSW = gunshot wound, PED = pedestrian struck by car, UNK = unknown mechanism.

View larger version (29K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2 —Bar graph shows distribution of imaging of head, cervical spine (c-spine), abdomen, and pelvis in patients with major injuries (dark bars) undergoing CT versus patients with minor or no injures (light bars) at imaging. Similar imaging utilization patterns were found in each of these subgroups.

Application of the ACR criteria was derived after accounting for accident severity, reported deaths at the scene, documented or possible loss of consciousness, drug and alcohol intoxication, presence of endotracheal intubations, presence of distracting injuries, and other reasons for inability to confidently perform history-taking and a physical examination.

For example, if a patient was involved in a motor vehicle collision and presented to the trauma service with a normal physical examination, vital signs, and Glasgow coma score, but had a possible loss of consciousness at the accident scene, any subsequent CT of the head would be considered to be indicated, whereas imaging of the cervical spine, abdomen, and pelvis would be classified as nonindicated. Under the previous scenario, if the patient was found to be intoxicated or under the influence of drugs, then all imaging would be considered to be indicated.

The average charge generated for each patient was also calculated. This charge was based on the fees billed to patients for both the technical and professional portions of the examinations. Although computed radiography (429 examinations) was performed on all patients in the study, the charge reported was based only on CT data. This method of determining cost was selected for ease of reproducibility and to eliminate any potential confusion between costs incurred by hospitals and physicians and costs incurred by the patient.

The Nuclear Regulatory Commission (NRC) is responsible for setting annual radiation exposure limits for radiation workers in the United States. These limits follow the as-low-as-reasonably-achievable or ALARA principle and set the upper limit at 50 mSv of whole-body equivalent per year for radiation workers and 1 mSv per year for the general population [3]. This difference is partially explained by the relative number of radiation workers compared with the general population. Medical radiation is specifically excluded from the limits imposed by the NRC on the basis of an assumption that the benefits greatly outweigh the risks for most medical applications.

CT radiation doses can be reported by absorbed dose, equivalent dose, or effective dose. The absorbed dose is the energy deposited in a volume of tissue divided by the mass of the tissue. This is reported in grays (Gy). The absorbed dose can be converted to equivalent dose based on a radiation weighting factor that is specific to the type of radiation being used; for most diagnostic applications, including CT, this factor is 1. The equivalent dose is reported in sieverts (Sv). Thus, the absorbed dose and the equivalent dose are the same for diagnostic CT.

A more useful way to report CT radiation dose is effective dose. This allows risk of cancer and genetic events from the equivalent dose to be estimated. The effective dose is also reported in sieverts or millisieverts and can be calculated by several methods. The most straightforward of these methods is to use the tissue-weighting factors published in the European Guidelines on Quality Criteria for Computed Tomography and is the method used in this study [4, 5]. The dose–length products (DLPs) stored in the radiology department's MDCT scanner (LightSpeed Plus, GE Healthcare) were used for the radiation estimate. The estimated radiation doses obtained in this manner were similar to values previously reported by more direct measurements and in other studies [6–10].

Results

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The patients could be separated into two groups based on the presence or absence of major injury. Ninety-six patients had identifiable major injuries, which were those classified as requiring surgical intervention or hospitalization. The remaining 104 patients could be subdivided on the basis of the presence of either no radiographically identifiable injury (n = 69) or minor injuries (n = 35). Minor injuries were defined as injuries that required only observational treatment, bedside intervention, or outpatient follow-up. For example, soft-tissue swelling, superficial lacerations, and isolated rib fractures were all considered to be minor injuries.

Imaging decisions were primarily protocol-driven, as is evidenced by the relatively small number of examinations of the chest, face, and neck. Overall, 169 of the 200 patients underwent CT. This included 88 (92%) of the 96 patients with major injuries and 81 (78%) of the 104 patients without major injuries. This difference was not statistically significant (p = 0.12). Of the 200 patients originally selected, eight patients were excluded from analysis of the ACR criteria on the basis of incomplete clinical data, but were included in overall cost and radiation calculations. These eight patients included two patients (eight total CT examinations including a CT examination of the pelvis and one of the face positive for major injury and a CT examination of the abdomen positive for minor injury) with major injuries at imaging, four patients (16 CT examinations) with no radiographically identifiable injury, and two patients (eight CT examinations: face with nasal bone fracture, abdomen with superficial laceration) with minor injuries.

When subdivided by body section imaged using standard Current Procedural Terminology (CPT) codes [11], a total of 660 CT examinations were performed for the patients in the study. The types of CT examinations ordered varied slightly depending on the underlying mechanism of injury. The most common mechanism of injury (98 patients) was motor vehicle collision (Fig. 1). Fall, gunshot wound, stabbing, and assault, together with motor vehicle collision, accounted for 166 of the 200 patients. CT of the head, cervical spine, abdomen, and pelvis were the most common examinations ordered after chest radiography (594/660). The remaining CT examinations included face (n = 24), neck (n = 4), and chest (n = 38). At least 50% (mean, 57%) of the patients injured by motor vehicle collision, crush injury, or fall had one or more major injuries. The remaining categories had fewer than 50% (mean, 20%) with major injuries. For those patients receiving CT imaging, there was no overall difference in the type or distribution of studies ordered regardless of the presence or absence of underlying injury (Fig. 2).

When the ACR appropriateness criteria were retrospectively applied to determine how CT would be affected, 44% of the studies ordered would not have been indicated (Tables 1 and 2). None of the major injuries identified on CT would have been excluded from imaging on the basis of the ACR criteria. However, 11 injuries classified as minor would not have been immediately imaged (Table 3). Of these 11 injuries, none required subsequent intervention. Seven of the 11 injuries were found in the thorax at the margin of the cervical spine or abdominal imaging. From the data available in the medical record, none of these injuries was clinically suspected, and none of the patients with these injuries had a CT examination of the chest.

Two false-positive examinations were retrospectively identified. One involved CT of the head and described findings of a possible closed head injury. The other was from CT of the abdomen in a gunshot victim with a superficial left flank gunshot wound. Here the possibility of intraperitoneal air was raised because of the close approximation of the ballistic track and associated air with the peritoneum and beam-hardening artifact from the bullet. In both of these cases, the patients were discharged after a short period of observation in the emergency department.

Radiation
Most patients undergoing CT had their studies performed on an MDCT scanner (LightSpeed Plus). During the study, the radiology department began concurrently using a LightSpeed Ultra scanner (GE Healthcare). For simplicity, because the CT protocols did not change, the radiation dose estimates were performed as if all patients had been examined on the LightSpeed Plus scanner. A radiation dose estimate (effective dose) for the typical trauma patient undergoing CT was calculated by multiplying the DLP for each CT examination by the appropriate tissue-weighting factor [4]. The average trauma patient in this study incurred a typical DLP of 2,885 mGy · cm from evaluation of the head, cervical spine, abdomen, or pelvis. This value converts to an effective dose of approximately 16 mSv (Table 4). A 16-mSv effective dose is similar to data obtained in prior studies, including those involving MDCT [4, 6, 9, 10, 12, 13].

Application of the ACR appropriateness criteria would have reduced the average effective dose in this study by 7 mSv, from 16 mSv per patient to 9 mSv. This represents an approximately 44% reduction in the overall radiation incurred.

Cost
A total of $837,028 in charges was generated, for an average of $4,953 per patient undergoing CT. Approximately $439,000 (52%) was charged for those patients with major injuries, whereas nearly $398,000 (48%) was charged for those patients without major injuries. The total amount required for the identification of each cervical spine fracture in the study was $18,763, and $17,390 was needed to identify each subdiaphragmatic visceral injury. These values would have been reduced to approximately $9,200 (51% reduction) and $9,700 (44% reduction), respectively, with application of the ACR criteria. No cervical spine injuries or subdiaphragmatic visceral injuries would have been excluded from imaging on the basis of these criteria (Fig. 3).

View larger version (26K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3 —Bar graph shows cost of imaging patients with major injuries versus patients without major injuries. "Potential cost savings" reflects potential amount saved if American College of Radiology appropriateness criteria had been applied to CT selection. Cost reflects charges incurred by uninsured individuals who were responsible for full health care bill.

Discussion

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The ACR appropriateness criteria were developed to guide both radiologists and clinicians in evaluating various types of patients, including victims of trauma. These imaging guidelines are freely available as a Web-based tool [2] and are being increasingly emphasized. This increasing use was most recently shown by the adoption of these guidelines by the largest private insurance provider in the United States [14]. Our study sought to better understand the potential impact of these recommendations on the imaging utilization pattern seen at an academic level 1 trauma center.

As can be seen from the data presented, the application of the ACR criteria to this cohort of patients would have resulted in reductions of nearly 44% of the overall radiation dose received and approximately 39% of the total fees charged. These results are comparable to the greater than 30% reduction in all types of CT examinations achieved for patients in Israel after the mandatory adoption of the ACR criteria by a large insurance carrier (Tal S et al., presented at the 2004 annual meeting of the Radiological Society of North America, Chicago, IL). The overall negative predictive value of the ACR criteria coupled with the history and physical examination was 100% in our study for major injuries. When minor injuries are included, the negative predictive value decreases slightly, to 96%.

The ability to confidently exclude underlying major traumatic injuries by the use of nationally accepted guidelines is of potentially great benefit to both physicians and patients and to the national health care system in general. This statement is highlighted by both the potential financial savings seen in the study ($325,000) and the potential reduction in radiation dose to the patient (7 mSv). Our cost estimates were based on the full fee charged to uninsured patients undergoing CT and were calculated with both the technical and professional components. Many victims of trauma are young and often uninsured. They are therefore liable for the full medical bill [15]. Patients with insurance through private or public means are not directly responsible for the full amount, and the actual reimbursement to the health care system is often less than the amount charged. With an average cost of nearly $5,000 per patient undergoing CT, the application of the ACR criteria to the imaging of the millions of trauma patients seen annually in the United States has the potential to save many billions of dollars. With medical expenses now estimated to account for nearly half of the bankruptcies declared annually in the United States, any reduction in charges is important for millions of uninsured and underinsured persons who face the possibility of paying a nondiscounted rate for medical care [16]. This reduction in charges is also important to public and private insurance carriers, and could free some of the financial, technical, and human resources currently used in the evaluation of trauma patients for others seeking care in the emergency department.

Perhaps even more important, the 44% reduction in radiation dose achieved by adherence to the ACR criteria could theoretically result in a reduction in radiation-induced cancer events by several thousand patients annually. The risk of cancer induction is based on the 16-mSv effective dose that the average patient sustained in our study. This effective dose falls within the range of increased risk of stochastic effects that were seen in some of the low-dose atomic bomb survivors, although this effective dose is less than the 29 mSv mean for the Hiroshima survivors [17]. A predicted slightly increased risk of future cancer death has been described at length in recently published papers, and, in adults, may correspond to approximately one cancer-related event per 1,250 patients [17, 18]. The U.S. Food and Drug Administration has published a rate of one cancer event per 2,000 patients receiving a 10-mSv effective dose [19]. It is important to recognize that the actual dose received by an individual patient is likely to be higher or lower based on many patient-specific and scanning-specific factors that cannot be known in a retrospective study and are often impossible to measure directly [8, 9, 20].

Radiation risk from diagnostic imaging is the subject of much controversy, and estimates of cancer induction and death should be evaluated with caution. The potential risk of cancer development and the risk of the deterministic effects of radiation have recently come to national attention in a series of publications and have resulted in attempts to reduce radiation dose through modulation of the CT technique itself [20–23]. However, the reduction in radiation exposure that can be achieved by the judicious selection of patients for CT has the potential to achieve a greater overall reduction than can be achieved through attempts at dose reduction through modulation of the peak kilo-voltage and tube current alone [24]. Coupling these two techniques for radiation reduction provides a greater opportunity to minimize patient exposure.

The 11 injuries that would not have resulted in imaging using strict adherence to the ACR criteria also deserve further discussion. As previously stated, none of these injuries was considered major, which was borne out by the subsequent patient outcomes. Although this is reassuring, it should not imply that a major injury could not be excluded using strict adherence to the ACR criteria. Conversely, one of the two false-positive examinations could have been avoided by the application of the ACR criteria. The impact of potential false-positive examinations on clinical decision making is as important to consider as the impact from false-negative results. Continued careful history-taking and physical examination remain a key component to the management of trauma patients because the weighted recommendations for imaging appropriateness given by the ACR depend on these clinical data.

Given the opportunity for significant cost savings and the increasing recognition that diagnostic radiology may play a small but measurable role in cancer induction, additional effort must be put forth to help identify patients at low risk of underlying injury in the emergency department and thereby avoid the radiation exposure and cost that these patients incur. When they are educated about the ACR appropriateness criteria, radiologists should be able to produce a significant cost and radiation savings in not only trauma patients but also other types of patients. Such a result was recently achieved for pediatric patients undergoing CT by the active participation of radiologists in the grand rounds and medical student and resident education of our clinical colleagues [25]. A similar result seems attainable for other areas of radiology practice, but will require a concerted effort on the part of radiologists and referring clinicians.

The major limitations of this study are its retrospective nature and the use of data from a single urban academic level 1 trauma center. In the future, additional prospective investigation involving multiple centers to include both academic and community hospital systems is suggested to confirm similar imaging utilization practices and to better categorize the potential strong positive impact that the ACR appropriateness criteria can play in the day-to-day imaging of even the most seriously ill patients.

References

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