- Email: [email protected]
Clinical Prediction of Emergency Cranial Computed Tomography Results
ORIGINAL CONTRIBUTION
Clinical Prediction of Emergency Cranial Computed Tomography Results From the Department of Radiology" and the Emergency Department, Department of Internal Medicine,* Jewish Hospital, Washington Umversity Medical Center, St Louis, Missouri. Received for publication April 12, 1993. Revisionsreceived June 23 and November 8, 1993. Acceptedfor publication November 17, 1993,
William R Reinus, MO*
Study purpose: To determine the ability of clinicians to pre-
Frank L Zwemer Jr, MD t
dict the results of emergency head computed tomography (CT) scans.
Methods: Clinicians requesting cranial CT scans from the emergency department prospectively filled out a form detailing their patients' complaints, possible diagnoses, and the likelihood of finding those diagnoses on CT.The results of the scans were catalogued according to diagnosis and classified as acutely abnormal, chronically abnormal, or normal. Resu|ts: Analysis of 536 consecutive patients showed a significant direct correlation between clinical prediction of CT abnormality and scan results. No definite differences in the ability to predict scan results were observed among different physician training levels. Thirty-six patients had acute abnormalities on CT despite a clinical prediction of remote or low likelihood. Conclusion: Although clinical predictions of CT abnormality correlate with actual CT results, the correlation is not adequateIV refined to rely on for selection of patients for emergency cranial CT scans. [Reinus WB, Zwemer FL Jr: Clinical prediction of emergency cranial computed tomography results. Ann EmergMedJune t994;23:12-/1-12-/8.]
JUNE 1994 23:6 ANNALS OF EMESGENCu MEDICINE
1271
CRANIAL
CT Reinus & Zwemer
INTRODUCTION
Many studies have evaluated the usefulness of emergency cranial computed tomography (CT) for a variety of clinical problems, including trauma, headaches, ischemia, and seizures. 1-10 A large proportion of the scans that are obtained to evaluate these problems show rio acute abnormality Most agree, however, that it is important to maintain a low threshold for obtaining CT to avoid missing significant but clinically silent pathology.4-&1144 Although several past analyses of common acute rleurologic clinical problems have suggested guidelines for obtaining a CT, no set of guidelines has had perfect sensitivity t,15-2~ Therefore, clinicians have had to individually tailor their decisions to obtain a CT to each patient's particular clinical situation. To our knowledge, no study has evaluated the ability of clinicians to predict CT findings from patients' clinical presentations. In this study, we attempt to analyze this relationship between clinical impression and the results of CT scans obtained for neurologic complaints.
substance. Dizziness was defined as a complaint of lightheadedness, positional or otherwise, without accompanying vertigo. The depressed sensorium variable was distinguished from unresponsiveness. A patient had to be totally unarousable to meet criteria for the unresponsiveness variable. Aside from the exceptions just noted, the clinical variables could be present in any combination. CT scans were performed on one of two General Electric 9800 scanners. All were obtained using a standard protocol with 1-cm collimation and 1-cm slice thickness. IV contrast was not given. All scans were interpreted by an attending radiologist. CT examinations were reviewed by one of the authors whenever a discrepancy existed between clinical and imaging data or an ambiguous or uncertain finding was described. This necessitated Table 1.
Study entryform 1. Reason for Head CT (please circle all findings that apply): PHYSICALFINDINGS MUST BE NEW OR ACUTELYWORSENED
MATERIALS
AND
METHODS
Cases were collected between January 14, 1992, and December 6, 1992, from a Level II emergency department that treats 26,000 patients per year and is in a major teaching hospital. In all patients for whom a head CT was requested, clinicians filled out a form before obtaining the CT. Data entered on the form included the clinical indication for the CT, the abnormality or abnormalities that the clinician suspected the scan would show, the clinician's prediction of the likelihood of finding an abnormality on the CT, and the clinician's specialty and postgraduate training level (Table 1). All predictions were scored on a 6-point scale from remote, which was scored as 1, through certain, which was scored as 6. Because the ED we studied is affiliated with a teaching institution, the majority of the forms were completed by medicine or neurology house officers, including residents and fellows, and by full-time ED attendings. Attending physicians staff the ED on a 24-hour basis and are always available for case consultation. The patients' histories and physical examinations were classified according to 37 major clinical variables (Table 1). Terminology was used in accordance with standard textbook definitions. 22 Hypertension was defined as a diastolic blood pressure of more than 90 mm Hg recorded on presentation to the ED. Intoxication was classified as positive based on a blood alcohol level equal to or more than 100 mg% or evidence of ingestion of other illicit
1 27 2
Agitation Amaurosis Amnesia Aphasia Apraxia Ataxia Babinski Bipolar disorder Blurred vision Cancer Cranial nerve dysfunction Depressed sensorium Disorientation Dizziness Facial nerve deficit only Other, Specify:
Fever T = ~ Focal motor deficit Focal sensory deficit Headache Headache, worst Hypertension BP = _ _ / _ Intoxication Loss of consciousness Neurologic deficit, resolved Neurologic deficit, unresolved Medicolegal
Paresthesias only Photophobia Romberg sign Schizophrenia Seizure, new onset Seizure, NOT new onset Slurred speech only
Trauma/motor vehicle accident Unresponsive Vertigo Weakness, generalized
2. Looking for (check all that apply): _ Abscess _ Cerebritis _ Fracture _ Hemorrhage, _ Hemorrhage, _ Hemorrhage, __ Hemorrhage, __ Hemorrhage, __ Hemorrhage,
__ Herniation, brain
subarachnoid intracranial intraparenchymal intraventricular subdurat epidural
_ Hydrocephalus _ Infarct _ Leukoencephalopathy _ Meningitis _ Tumor, metastasis _ Tumor, primary _ Other: _ _
3. Likelihood of Finding Suspected Abnormality: Remote (1) < 5% Low (2) 5% to 15% Moderate (3) > 15% to 45%
Moderate high (4) > 45% to 85% High (5) > 85% to 95% Certain (6) > 95%
4. Ordering Physician and Training Level: Medicine: PGY _ Attending Neurology: PGY _ Attending
ED: Attending Neuresurgery: PGY _ Attending
ANNALS OF EMERGENCY MEDICINE
23:6
JUNE 1994
C R A N I A L CT Reinus & Zwemer
review of 5% to 10% of the scans. Discrepancies were resolved wherever possible by evaluation of followup imaging studies, either CT or magnetic resonance imaging. Scans were classified as acutely positive on finding intracalvarial abnormalities, either axial or extra-axial, which could not be shown to be chronic by either virtue of appearance or the availability of prior scans. Scans were classified as chronically abnormal whenever a lesion was judged to be long-standing by virtue of its appearance or
presence on prior scans. Thus, a well-defined lucency in a vascular distribution consistent with an infarction accompanied by associated enlargement of adjacent cerebrospinal fluid spaces would be considered chronic even in the absence of a prior CT. If an acute finding coexisted with a chronic finding, the Scan was classified as acutely abnormal. We conducted analyses for the group as a whole and by training level. We analyzed first- and second-year postgraduate physicians, third-year postgraduate physi-
Table 2.
CT result versus clinical prediction CT Result Prediction
Negative
Chronic
Acute
Total
Remote (< 5%) Low (5% to 15%) Moderate (> 15% to 45%) Moderate high (> 45% to 85%) High (> 85% to 95%) Certain (> 95%) Total Valuesindicatenumberof patients(%).
29 (5.4) 98 (18.3) 70 (13.1) 13 (2.4) 5 (0.9) 1 (0,2) 216 (40.3)
23 (4.3) 61 (11.4) 74 (13.8) 27 (5.0) 9 (1.7) 3 (0.8) 197 (36.8)
4 (0.7) 32 (6.0) 46 (8.6) 17 (3.2) 18 (3.4) 6 (1.1) 123 (22.9)
56 (10.4) 191 (35.6) 190 (35.4) 57 (10.6) 32 (6.0) 10 (1.9) 536 (100.0)
Figure 1.
Graph of percent of cases in each CT result category by clinical prediction for all patients %
100 90 80 70 60 50 4G 30 20 10 0
LOW
I BI CT:AcuteAbnormality
IVloderate Moderate High Predictionof AcuteCTAbnormality [ ] CT:ChronicAbnormality
Pltgn
[ ] CT:Negative
I
Numbersin graphcolumnsrepresentabsolutenumberof datapoints,
JUNE 1994
23:6
ANNALS OF EMERGENCY MEOICINE
1273
CRANIAL CT
Reinus & Zwemer
clans through fellows, and attendings separately. Although specialty was recorded, there was not enough variation in physician specialization to allow analysis by specialty. We subdivided our entire sample according to findings on neurologic examination and repeated our analyses for those patients without neurologic findings. We also selected the groups of patients with complaints of headache, seizure, and trauma for separate analyses. We compared the physicians' predicted CT findings with the actual CT findings for cases where there was an acutely abnormal CT. Categories considered included infarct, subarachnoid hemorrhage (SAH), subdural or epidural hemorrhage (SDH/EDH), intracranial or intraventricular hemorrhage (ICI-t/IVH), tumor, and other. To be considered a match, a finding on the CT had to have been considered in the clinician's differential. Therefore, a clinician who suspected either an infarct or SAH would
have been scored as a match if the CT showed either or both of these findings. Two-way factorial analysis of variance, Tukey's HSD (SAS Institute Inc, Cary, North Carolina), %2 tests, and receiver operator curve (ROC) analysis using a univariate Z-score test 23 were used where applicable. The P values obtained were used as measures of the strength of the evidence against the null hypothesis tested. Values of P < .05 were considered statistically significant, with moderate evidence against the null hypothesis. Values of P < .01 were considered strong evidence against the null hypothesis. RESULTS
We collected data on 550 consecutive patients who underwent cranial CT out of the ED. Fourteen cases had incomplete forms and so were excluded from analysis. We assumed a missing at random basis for the data and used the remaining cases for analysis. Analysis of Prediction: All Cases The correlation between predicted CT results and actual CT results is given for the entire sample (Table 2). There were 123 CT scans (22.9%) with acute abnormalities and 197 CT scans (36.8%) with chronic abnormalities. The remaining 216 scans (40.3%) were normal. Graphic display of the data in Table 2 shows that as the predicted probability of an abnormal CT increased, so did the relative percentage of acutely abnormal CT scans (Figure 1). This association was highly significant (Tukey's HSD, P = .0001). In addition, pairwise testing of each possible pair of CT classifications (acute, chronic, and negative) by level of clinical prediction showed statistical significance in every case (Tukey's HSD, P < .05). Thus, as the level of CT abnormality worsened, so did the clinicians' suspicion of abnormality. Even so, there were 36 scans with acute abnormalities despite prediction of remote or low probability of an abnormality by the ordering physician. Requests for these 36 cases did not come disproportionately from less-expe-
Figure 2.
ROCs for prediction of acute CT abnormality by training level True-PositiveFraction 1.0
.>.: .: ,:. :: .;,,~ %-~'L-"................
0.8
~ , , t *'~
0.6
0.4 j
0,0 ~' I'e''''''"
.."
'
0.2
' 0.4
'
' 0.6
'
' 0.8
'
' 1.0
False-PositiveFraction
Table 3,
Predicted versus actual CT result by pathologc category Actual CT Result
Match with predicted result No match with predicted result
Infarct
SAH
SDH/EDH
ICH/IVH
Tumor
Other
Total
46 15
1 1
1 3
14 7
15 10
5 5
82 41
2
4
21
25
10
123
50.0
25.0
66.7
60.0
50.0
Total
61
Corrected (%)
75.4
12 7 4
ANNALS OF EMERGENCY MEDICINE
66.7
23:6
JUNE 1994
CRANIAL CT Reinus & Zwemer
rienced physicians (Z2, P =. 11). Included in this group were 18 early infarcts, eight mass lesions, three parenchymal hemorrhages, three subdural hematomas, two patients with previously unrecognized hydrocephalus, one basilar skull fracture, and one patient with a giant cerebral aneurysm arising from the tip of the right internal carotid artery. The mass lesions, all previously undiagnosed, included three patients with metastatic disease, two with primary tumors, and three with small meningiomas that were believed to be incidental in every case. Analysis by Training Level of Physician There was an overall significant difference among training level groupings with respect to the magnitude of prediction of CT abnormality (Tukey%HSD, P = .02). In general, the least-experienced physicians tended to assign higher probabilities of acute abnormality for CT scans (average prediction magnitude, 2.8) than did more-experienced physicians (average prediction magnitude, 2.6). However, pairwise testing of the training level groupings with respect to prediction of scan findings showed no significance. Although a trend was suggested, we could show no significant interaction between training level and CT results with respect to prediction of CT findings (Tukey's HSD, P = .07). Therefore, clinicians at all levels of training, despite mild differences in overall level of estimation,
appear to have a sense of the likelihood of finding an acute abnormality on CT. ROC analysis confirmed this concept. The similarity of the shapes of the curves and areas below the curve for each training level indicates similar sensitivity and specificity for a CT abnormality among the tested physician experience levels (Figure 2). These areas did not differ significantly for any pairwise test comparing the training level groupings. Analysis by Result of Neurologic Examination As expected, the average predicted likelihood of an acute CT abnormality was significantly higher in patients with neurologic findings (average prediction magnitude, 3.2) than in those without (average prediction magnitude, 2.5) (analysis of variance, P < 1 x 104~ We repeated evaluation of clinical prediction versus scan result for the 357 patients without positive neurologic findings. We again observed a direct correlation between predicted and actual CT results (Tukey's HSD, P = .0001). Even in this group, however, 25 patients with acutely abnormal CT scans had clinical predictions of remote or low likelihood of a CT abnormality. Analysis by Complaints of Headache, Seizure and Trauma We also evaluated clinical ability to predict CT results with respect to three specific complaints: headache (n = 106) (Figure 3), seizure (n = 56) (Figure 4), and head trauma
Figure3. Graph of percent of cases in each CT result category by clinical prediction of abnormality for patients with a complaint of headache 100
80
60
40
20
Kemote
LOW
[ ] CT: Acute Abnormality
Moaerate
Moderate High Prediction of CT Abnormality []
CT: Chronic Abnormality
Certain
Illgn
[ ] CT:Negative
I
Numbersin graph columns represent absolute number of data points,
JUNE 1994 23:6 ANNALS OF EMERGENCY MEDICINE
1275
CRANIAL CT
Reinus & Zwemer
Figure 4.
Graph of percent of cases in each CT result category by clinical prediction of abnormality for patients with a complaint of seizure 100 90 80
70 60 50 40 30 20 10 0
Nemote
LOW
I
Moderate Moderate High Probabilityof Acute CTAbnormality
~ CT:AcuteAbnormality
High
[ ] CT:ChronicAbnormality
l, ercaln
[ ] CT:Negative
I
Numbersin graphcolumnsrepresentabsolutenumberof data points.
Figure 5.
Graph of percent of cases in each CT result category by clinical prediction of abnormality for patients with a complaint of trauma % 100 90 80 70 60 50 40 30 20 10 0
LOW
Moderate
tltgn
Moderate High
Probabilityof Acute CTAbnormality [ ] CT:AcuteAbnormality
~
CT:ChronicAbnormality
[ ] CT:Negative
1
Numbersin graphcolumnsrepresentabsolutenumberof data points.
1276
ANNALS OF EMERGENCY MEDICINE
23:6
JUNE 1994
C R A N I A L CT Remus & Zweme*
I III
(n = 85) (Figure 5). Among these three complaints, we found a significant relationship between the predicted likelihood of CT abnormality and the actual CT classification only for the complaint of headache (%2, p = .0115). No statistical relationship was found between a suspicion of CT abnormality and eventual CT classification for either complaint of seizure or trauma. Analysis by Prediction of PathologyType Finally, we evaluated clinical ability to correctly predict the type of pathology on acutely positive CT scans (Table 3). Overall, the correct category was predicted in 82 of the 123 acutely positive scans (66.7%). Performance was best for infarcts with a match in 75.4% of cases. SDH/EDH and SAH were sparsely represented in our sample, so evaluation of these lesions may not be accurate. DISCUSSION
Our data show that clinicians' predictions of acute abnormalities on cranial CT generally coincide with the findings on the scan. Despite this fact, 29.2% of the acutely positive scans were in the remote or low prediction categories. In the sample of patients whose neurologic examinations were negative, 36.7% of the acutely positive scans were in the remote or low likelihood categories, a higher percentage than for the entire sample. This percentage increase is statistically significant (%2, p < .003), indicating that it is even more difficult to predict CT outcome in the absence of neurologic findings. It is precisely this difficulty that has caused many clinicians to have an extremely low threshold for obtaining a CT, particularly m an emergency setting where the patient is not well known to the physician.2-9, 2 4 Eighteen of the acutely positive scans (50%) in the remote or low likelihood categories showed early or new infarctions, and most likely the patients' courses were not significantly altered by the CT results. On the other hand, eight of these scans (22.2%) showed masses, five of which were clinically significant. Six additional scans (16.7%) showed intracranial hemorrhage, and two scans (5.6%) showed newly diagnosed hydrocephalus. Discovery of these lesions made a significant difference to the disposition of these patients from the ED. We found no interaction between training level and prediction of CT abnormality. It appears that the ability to predict CT results did not improve significantly with increasing experience. Again, this is corroborated by the similar ROC curves developed for each training level group with respect to prediction of an acute CT abnormality (Figure 2). However, this conclusion must be
JUNE 1994 23:6
ANNALS OF EMER6ENCY MEDICINE
guarded because there is a supervising attending present in the ED on a 24-hour-a-day basis. We could not control for the possibility that consultation between attendings and junior residents may have obscured a relationship between ability to predict scan results and training level. Despite the overall correlation between prediction of CT abnormality and eventual findings, the subgroups of patients with seizure (Figure 4) and trauma (Figure 5) did not show similar correlations. The exact reason for this is uncertain. It may be a function of the size of these subgroups, but we believe this is unlikely. In the trauma group, all acutely abnormal studies, except one infarction, had predictions of abnormality in the remote or low likelihood categories. In the patients with seizure, all the cases except one subdural hematoma had clinical predictions of CT abnormality, at least in the moderate range. Thus, although we could show no correlation between prediction and actual result for the seizure group, it appears that there was a higher clinical suspicion of which patients would actually have an abnormal CT in this group than in the trauma group. Clinical predictions of the type of pathology matched actual results 66.7% of the time. That the abnormality seen on CT was different than expected one-third of the time suggests that it is often difficult to identify the underlying pathology causing the patientg clinical complaint. CONCLUSION
Although our data show a definite relationship between prediction of CT abnormality and actual CT result, it clearly is not adequately refined to allow patient selection for CT based solely on clinical impression. Previous studies have argued for the use of various algorithms to guide clinicians in choosing patients for CT. 11-13,15.16 Others have suggested the liberal use of CT in ED patients with even minimal head trauma. 4-8'14 To date, no study has been able to show perfect sensitivity for the selection of patients with intracranial abnormalities without performance of a large proportion of negative examinations. Although it is clear that a large number of negative scans are being performed at a great financial cost, our current data do not provide an alternative to a low threshold for CT to avoid missing clinically silent but potentially lethal pathology. REFERENCES 1. Sexton CO, Caples C: EmergencyCT of the head: Indications and utilization. MdMedJ 1987;36:493-495.
1277
C R A N I A L CT Reinus & Zwemer
2. Mills ML, RussoLS, Ross BA: High-yield criteria for urgent cranial computed tomography scans. Ann EmergMed 1986;15:1167-1172. 3. Harrup SN: Head scanning during admission through the accident and emergency department. Injury1983;14:465-470. 4. Livingston DH, Loder PA, Kozinl J, et al: The use of CT scanning to triage patients requiring admission following minimal head injury. J Trauma1991;31:483-489. 5. Stein SC, RossSE: The value of computed tomographic scans in patients with low-risk head injuries. Neurosurgery1990;26:538-640. 6. FeuermanT, Ashley P, Gade FG, at al: Value of skull radiography, head computed tomographic scanning and admission for observation in cases of minor head injury. Neurosurgery 1988;22:449-453.
C o p y r i g h t 9 by t h e A m e r i c a n College o f E m e r g e n c y P h y s i c i a n s R e p r i n t no. 47/1/55407 Address for reprints: William R Reinus, MD Associate Professor Jewish Hospital Maltinckrodt Institute of Radiology Washington University Medical Center
7. Dacey RG Jr, Alves WM, Rimel RW, et al: Neurosurgical complications after apparently minor head injury. J Neurosurg1986;65:203-210.
215 S Kingshighway
8. Harad IT, Kerstein MD: Inadequacyof bedside clinical indicators in identifying significant intracranial injury in trauma patients. J Trauma1992;32:359-363.
314-454-7400
9. McMicken DB: EmergencyCT head scans in traumatic and atraumatic conditions. Ann Emerg Med1986;15:274-279.
St Louis, Missouri 53110
Fax 314454-5262
10. Wood LP, Parisi M, Finch IJ: Value of contrast enhanced CT scanning in the non-trauma emergencyroom patient. Neuroradiology1990;32:261-264. 11. Ramirez-LassepasM, Cipolle RJ, Morillo LR, et al: Value of computed tomographic scan in the evaluation of adult patients after their first seizure. Ann Neuro11984;15:536-543. 12. Young AC, Mohr PD, Borg CostanziJ, et al: is routine computerised axial tomography in epilepsy worth while? Lancet1982;2:1446-1447. 13. van Donselaar CA, Geerts AT, SchimsheimerR: Idiopathic first seizure in adult life: Who should be treated? BMJ 1991;302:620-623. 14. Livingston DH, Loder PA, Hunt CD: Minimal head injury: Is admission necessary?Am Surg 1991;57:14-17. 15. Vydareny K, Harle T, Potchen EJ: An algorithmic approach to the roentgenographicevaluation of head trauma: Medical and financial implications. InvestRadio11983;4:390-395. 16. French BN, Dublin AB: The value of computerizedtomography in the management of 1000 consecutive heed injuries, SurgNeurol1977;7:171-183. 17. Eisner RF,Turnbull TL, Howes DS, et al: Efficacy of "standard"seizure workup in the emergencydepartment. Ann EmergMed 1986;15:33-39. 18. RussoLS, Goldstein KH: CT evaluation in patients after first seizure. Ann Neuro11985;17:618619. 19. KnausWA, Wagner DP, Davis DO: CT for headache:Cost/benefit for subarachnoid hemorrhage.Am J Radiol1981;136:537-542. 20. GrosskreutzSR, OsbornRE, SanchezRM: Computedtomography of the brain in the evaluation of the headachepatient. Milit Med 1991;156:137-I48. 21. Baker HL Jr: Cranial CT in the investigation of headache:Cost-effectivenessfor brain tumors J Neuroradio11983;10:112-116. 22. Adams RD, Victor M: Principlesof Neurology,ed 4. New York, McGraw-Hill, 1989. 23. Swets JA, Pickett RM: Evaluationof DiagnosticSystems:MethodsFromSignalDetection Theory.New York, Academic Press,1982. 24. Adams HP, Kassell NF, Torner JC, et al: CT and clinical correlations in recent aneurysmal subaraohnoidhemorrhage:A preliminary report of the CooperativeAneurysm Study. Neurology 1983;33:981-988.
1 27 8
ANNALS OF EMERGENCY MEDICINE
23:6
JUNE 1994
Clinical Prediction of Emergency Cranial Computed Tomography Results From the Department of Radiology" and the Emergency Department, Department of Internal Medicine,* Jewish Hospital, Washington Umversity Medical Center, St Louis, Missouri. Received for publication April 12, 1993. Revisionsreceived June 23 and November 8, 1993. Acceptedfor publication November 17, 1993,
William R Reinus, MO*
Study purpose: To determine the ability of clinicians to pre-
Frank L Zwemer Jr, MD t
dict the results of emergency head computed tomography (CT) scans.
Methods: Clinicians requesting cranial CT scans from the emergency department prospectively filled out a form detailing their patients' complaints, possible diagnoses, and the likelihood of finding those diagnoses on CT.The results of the scans were catalogued according to diagnosis and classified as acutely abnormal, chronically abnormal, or normal. Resu|ts: Analysis of 536 consecutive patients showed a significant direct correlation between clinical prediction of CT abnormality and scan results. No definite differences in the ability to predict scan results were observed among different physician training levels. Thirty-six patients had acute abnormalities on CT despite a clinical prediction of remote or low likelihood. Conclusion: Although clinical predictions of CT abnormality correlate with actual CT results, the correlation is not adequateIV refined to rely on for selection of patients for emergency cranial CT scans. [Reinus WB, Zwemer FL Jr: Clinical prediction of emergency cranial computed tomography results. Ann EmergMedJune t994;23:12-/1-12-/8.]
JUNE 1994 23:6 ANNALS OF EMESGENCu MEDICINE
1271
CRANIAL
CT Reinus & Zwemer
INTRODUCTION
Many studies have evaluated the usefulness of emergency cranial computed tomography (CT) for a variety of clinical problems, including trauma, headaches, ischemia, and seizures. 1-10 A large proportion of the scans that are obtained to evaluate these problems show rio acute abnormality Most agree, however, that it is important to maintain a low threshold for obtaining CT to avoid missing significant but clinically silent pathology.4-&1144 Although several past analyses of common acute rleurologic clinical problems have suggested guidelines for obtaining a CT, no set of guidelines has had perfect sensitivity t,15-2~ Therefore, clinicians have had to individually tailor their decisions to obtain a CT to each patient's particular clinical situation. To our knowledge, no study has evaluated the ability of clinicians to predict CT findings from patients' clinical presentations. In this study, we attempt to analyze this relationship between clinical impression and the results of CT scans obtained for neurologic complaints.
substance. Dizziness was defined as a complaint of lightheadedness, positional or otherwise, without accompanying vertigo. The depressed sensorium variable was distinguished from unresponsiveness. A patient had to be totally unarousable to meet criteria for the unresponsiveness variable. Aside from the exceptions just noted, the clinical variables could be present in any combination. CT scans were performed on one of two General Electric 9800 scanners. All were obtained using a standard protocol with 1-cm collimation and 1-cm slice thickness. IV contrast was not given. All scans were interpreted by an attending radiologist. CT examinations were reviewed by one of the authors whenever a discrepancy existed between clinical and imaging data or an ambiguous or uncertain finding was described. This necessitated Table 1.
Study entryform 1. Reason for Head CT (please circle all findings that apply): PHYSICALFINDINGS MUST BE NEW OR ACUTELYWORSENED
MATERIALS
AND
METHODS
Cases were collected between January 14, 1992, and December 6, 1992, from a Level II emergency department that treats 26,000 patients per year and is in a major teaching hospital. In all patients for whom a head CT was requested, clinicians filled out a form before obtaining the CT. Data entered on the form included the clinical indication for the CT, the abnormality or abnormalities that the clinician suspected the scan would show, the clinician's prediction of the likelihood of finding an abnormality on the CT, and the clinician's specialty and postgraduate training level (Table 1). All predictions were scored on a 6-point scale from remote, which was scored as 1, through certain, which was scored as 6. Because the ED we studied is affiliated with a teaching institution, the majority of the forms were completed by medicine or neurology house officers, including residents and fellows, and by full-time ED attendings. Attending physicians staff the ED on a 24-hour basis and are always available for case consultation. The patients' histories and physical examinations were classified according to 37 major clinical variables (Table 1). Terminology was used in accordance with standard textbook definitions. 22 Hypertension was defined as a diastolic blood pressure of more than 90 mm Hg recorded on presentation to the ED. Intoxication was classified as positive based on a blood alcohol level equal to or more than 100 mg% or evidence of ingestion of other illicit
1 27 2
Agitation Amaurosis Amnesia Aphasia Apraxia Ataxia Babinski Bipolar disorder Blurred vision Cancer Cranial nerve dysfunction Depressed sensorium Disorientation Dizziness Facial nerve deficit only Other, Specify:
Fever T = ~ Focal motor deficit Focal sensory deficit Headache Headache, worst Hypertension BP = _ _ / _ Intoxication Loss of consciousness Neurologic deficit, resolved Neurologic deficit, unresolved Medicolegal
Paresthesias only Photophobia Romberg sign Schizophrenia Seizure, new onset Seizure, NOT new onset Slurred speech only
Trauma/motor vehicle accident Unresponsive Vertigo Weakness, generalized
2. Looking for (check all that apply): _ Abscess _ Cerebritis _ Fracture _ Hemorrhage, _ Hemorrhage, _ Hemorrhage, __ Hemorrhage, __ Hemorrhage, __ Hemorrhage,
__ Herniation, brain
subarachnoid intracranial intraparenchymal intraventricular subdurat epidural
_ Hydrocephalus _ Infarct _ Leukoencephalopathy _ Meningitis _ Tumor, metastasis _ Tumor, primary _ Other: _ _
3. Likelihood of Finding Suspected Abnormality: Remote (1) < 5% Low (2) 5% to 15% Moderate (3) > 15% to 45%
Moderate high (4) > 45% to 85% High (5) > 85% to 95% Certain (6) > 95%
4. Ordering Physician and Training Level: Medicine: PGY _ Attending Neurology: PGY _ Attending
ED: Attending Neuresurgery: PGY _ Attending
ANNALS OF EMERGENCY MEDICINE
23:6
JUNE 1994
C R A N I A L CT Reinus & Zwemer
review of 5% to 10% of the scans. Discrepancies were resolved wherever possible by evaluation of followup imaging studies, either CT or magnetic resonance imaging. Scans were classified as acutely positive on finding intracalvarial abnormalities, either axial or extra-axial, which could not be shown to be chronic by either virtue of appearance or the availability of prior scans. Scans were classified as chronically abnormal whenever a lesion was judged to be long-standing by virtue of its appearance or
presence on prior scans. Thus, a well-defined lucency in a vascular distribution consistent with an infarction accompanied by associated enlargement of adjacent cerebrospinal fluid spaces would be considered chronic even in the absence of a prior CT. If an acute finding coexisted with a chronic finding, the Scan was classified as acutely abnormal. We conducted analyses for the group as a whole and by training level. We analyzed first- and second-year postgraduate physicians, third-year postgraduate physi-
Table 2.
CT result versus clinical prediction CT Result Prediction
Negative
Chronic
Acute
Total
Remote (< 5%) Low (5% to 15%) Moderate (> 15% to 45%) Moderate high (> 45% to 85%) High (> 85% to 95%) Certain (> 95%) Total Valuesindicatenumberof patients(%).
29 (5.4) 98 (18.3) 70 (13.1) 13 (2.4) 5 (0.9) 1 (0,2) 216 (40.3)
23 (4.3) 61 (11.4) 74 (13.8) 27 (5.0) 9 (1.7) 3 (0.8) 197 (36.8)
4 (0.7) 32 (6.0) 46 (8.6) 17 (3.2) 18 (3.4) 6 (1.1) 123 (22.9)
56 (10.4) 191 (35.6) 190 (35.4) 57 (10.6) 32 (6.0) 10 (1.9) 536 (100.0)
Figure 1.
Graph of percent of cases in each CT result category by clinical prediction for all patients %
100 90 80 70 60 50 4G 30 20 10 0
LOW
I BI CT:AcuteAbnormality
IVloderate Moderate High Predictionof AcuteCTAbnormality [ ] CT:ChronicAbnormality
Pltgn
[ ] CT:Negative
I
Numbersin graphcolumnsrepresentabsolutenumberof datapoints,
JUNE 1994
23:6
ANNALS OF EMERGENCY MEOICINE
1273
CRANIAL CT
Reinus & Zwemer
clans through fellows, and attendings separately. Although specialty was recorded, there was not enough variation in physician specialization to allow analysis by specialty. We subdivided our entire sample according to findings on neurologic examination and repeated our analyses for those patients without neurologic findings. We also selected the groups of patients with complaints of headache, seizure, and trauma for separate analyses. We compared the physicians' predicted CT findings with the actual CT findings for cases where there was an acutely abnormal CT. Categories considered included infarct, subarachnoid hemorrhage (SAH), subdural or epidural hemorrhage (SDH/EDH), intracranial or intraventricular hemorrhage (ICI-t/IVH), tumor, and other. To be considered a match, a finding on the CT had to have been considered in the clinician's differential. Therefore, a clinician who suspected either an infarct or SAH would
have been scored as a match if the CT showed either or both of these findings. Two-way factorial analysis of variance, Tukey's HSD (SAS Institute Inc, Cary, North Carolina), %2 tests, and receiver operator curve (ROC) analysis using a univariate Z-score test 23 were used where applicable. The P values obtained were used as measures of the strength of the evidence against the null hypothesis tested. Values of P < .05 were considered statistically significant, with moderate evidence against the null hypothesis. Values of P < .01 were considered strong evidence against the null hypothesis. RESULTS
We collected data on 550 consecutive patients who underwent cranial CT out of the ED. Fourteen cases had incomplete forms and so were excluded from analysis. We assumed a missing at random basis for the data and used the remaining cases for analysis. Analysis of Prediction: All Cases The correlation between predicted CT results and actual CT results is given for the entire sample (Table 2). There were 123 CT scans (22.9%) with acute abnormalities and 197 CT scans (36.8%) with chronic abnormalities. The remaining 216 scans (40.3%) were normal. Graphic display of the data in Table 2 shows that as the predicted probability of an abnormal CT increased, so did the relative percentage of acutely abnormal CT scans (Figure 1). This association was highly significant (Tukey's HSD, P = .0001). In addition, pairwise testing of each possible pair of CT classifications (acute, chronic, and negative) by level of clinical prediction showed statistical significance in every case (Tukey's HSD, P < .05). Thus, as the level of CT abnormality worsened, so did the clinicians' suspicion of abnormality. Even so, there were 36 scans with acute abnormalities despite prediction of remote or low probability of an abnormality by the ordering physician. Requests for these 36 cases did not come disproportionately from less-expe-
Figure 2.
ROCs for prediction of acute CT abnormality by training level True-PositiveFraction 1.0
.>.: .: ,:. :: .;,,~ %-~'L-"................
0.8
~ , , t *'~
0.6
0.4 j
0,0 ~' I'e''''''"
.."
'
0.2
' 0.4
'
' 0.6
'
' 0.8
'
' 1.0
False-PositiveFraction
Table 3,
Predicted versus actual CT result by pathologc category Actual CT Result
Match with predicted result No match with predicted result
Infarct
SAH
SDH/EDH
ICH/IVH
Tumor
Other
Total
46 15
1 1
1 3
14 7
15 10
5 5
82 41
2
4
21
25
10
123
50.0
25.0
66.7
60.0
50.0
Total
61
Corrected (%)
75.4
12 7 4
ANNALS OF EMERGENCY MEDICINE
66.7
23:6
JUNE 1994
CRANIAL CT Reinus & Zwemer
rienced physicians (Z2, P =. 11). Included in this group were 18 early infarcts, eight mass lesions, three parenchymal hemorrhages, three subdural hematomas, two patients with previously unrecognized hydrocephalus, one basilar skull fracture, and one patient with a giant cerebral aneurysm arising from the tip of the right internal carotid artery. The mass lesions, all previously undiagnosed, included three patients with metastatic disease, two with primary tumors, and three with small meningiomas that were believed to be incidental in every case. Analysis by Training Level of Physician There was an overall significant difference among training level groupings with respect to the magnitude of prediction of CT abnormality (Tukey%HSD, P = .02). In general, the least-experienced physicians tended to assign higher probabilities of acute abnormality for CT scans (average prediction magnitude, 2.8) than did more-experienced physicians (average prediction magnitude, 2.6). However, pairwise testing of the training level groupings with respect to prediction of scan findings showed no significance. Although a trend was suggested, we could show no significant interaction between training level and CT results with respect to prediction of CT findings (Tukey's HSD, P = .07). Therefore, clinicians at all levels of training, despite mild differences in overall level of estimation,
appear to have a sense of the likelihood of finding an acute abnormality on CT. ROC analysis confirmed this concept. The similarity of the shapes of the curves and areas below the curve for each training level indicates similar sensitivity and specificity for a CT abnormality among the tested physician experience levels (Figure 2). These areas did not differ significantly for any pairwise test comparing the training level groupings. Analysis by Result of Neurologic Examination As expected, the average predicted likelihood of an acute CT abnormality was significantly higher in patients with neurologic findings (average prediction magnitude, 3.2) than in those without (average prediction magnitude, 2.5) (analysis of variance, P < 1 x 104~ We repeated evaluation of clinical prediction versus scan result for the 357 patients without positive neurologic findings. We again observed a direct correlation between predicted and actual CT results (Tukey's HSD, P = .0001). Even in this group, however, 25 patients with acutely abnormal CT scans had clinical predictions of remote or low likelihood of a CT abnormality. Analysis by Complaints of Headache, Seizure and Trauma We also evaluated clinical ability to predict CT results with respect to three specific complaints: headache (n = 106) (Figure 3), seizure (n = 56) (Figure 4), and head trauma
Figure3. Graph of percent of cases in each CT result category by clinical prediction of abnormality for patients with a complaint of headache 100
80
60
40
20
Kemote
LOW
[ ] CT: Acute Abnormality
Moaerate
Moderate High Prediction of CT Abnormality []
CT: Chronic Abnormality
Certain
Illgn
[ ] CT:Negative
I
Numbersin graph columns represent absolute number of data points,
JUNE 1994 23:6 ANNALS OF EMERGENCY MEDICINE
1275
CRANIAL CT
Reinus & Zwemer
Figure 4.
Graph of percent of cases in each CT result category by clinical prediction of abnormality for patients with a complaint of seizure 100 90 80
70 60 50 40 30 20 10 0
Nemote
LOW
I
Moderate Moderate High Probabilityof Acute CTAbnormality
~ CT:AcuteAbnormality
High
[ ] CT:ChronicAbnormality
l, ercaln
[ ] CT:Negative
I
Numbersin graphcolumnsrepresentabsolutenumberof data points.
Figure 5.
Graph of percent of cases in each CT result category by clinical prediction of abnormality for patients with a complaint of trauma % 100 90 80 70 60 50 40 30 20 10 0
LOW
Moderate
tltgn
Moderate High
Probabilityof Acute CTAbnormality [ ] CT:AcuteAbnormality
~
CT:ChronicAbnormality
[ ] CT:Negative
1
Numbersin graphcolumnsrepresentabsolutenumberof data points.
1276
ANNALS OF EMERGENCY MEDICINE
23:6
JUNE 1994
C R A N I A L CT Remus & Zweme*
I III
(n = 85) (Figure 5). Among these three complaints, we found a significant relationship between the predicted likelihood of CT abnormality and the actual CT classification only for the complaint of headache (%2, p = .0115). No statistical relationship was found between a suspicion of CT abnormality and eventual CT classification for either complaint of seizure or trauma. Analysis by Prediction of PathologyType Finally, we evaluated clinical ability to correctly predict the type of pathology on acutely positive CT scans (Table 3). Overall, the correct category was predicted in 82 of the 123 acutely positive scans (66.7%). Performance was best for infarcts with a match in 75.4% of cases. SDH/EDH and SAH were sparsely represented in our sample, so evaluation of these lesions may not be accurate. DISCUSSION
Our data show that clinicians' predictions of acute abnormalities on cranial CT generally coincide with the findings on the scan. Despite this fact, 29.2% of the acutely positive scans were in the remote or low prediction categories. In the sample of patients whose neurologic examinations were negative, 36.7% of the acutely positive scans were in the remote or low likelihood categories, a higher percentage than for the entire sample. This percentage increase is statistically significant (%2, p < .003), indicating that it is even more difficult to predict CT outcome in the absence of neurologic findings. It is precisely this difficulty that has caused many clinicians to have an extremely low threshold for obtaining a CT, particularly m an emergency setting where the patient is not well known to the physician.2-9, 2 4 Eighteen of the acutely positive scans (50%) in the remote or low likelihood categories showed early or new infarctions, and most likely the patients' courses were not significantly altered by the CT results. On the other hand, eight of these scans (22.2%) showed masses, five of which were clinically significant. Six additional scans (16.7%) showed intracranial hemorrhage, and two scans (5.6%) showed newly diagnosed hydrocephalus. Discovery of these lesions made a significant difference to the disposition of these patients from the ED. We found no interaction between training level and prediction of CT abnormality. It appears that the ability to predict CT results did not improve significantly with increasing experience. Again, this is corroborated by the similar ROC curves developed for each training level group with respect to prediction of an acute CT abnormality (Figure 2). However, this conclusion must be
JUNE 1994 23:6
ANNALS OF EMER6ENCY MEDICINE
guarded because there is a supervising attending present in the ED on a 24-hour-a-day basis. We could not control for the possibility that consultation between attendings and junior residents may have obscured a relationship between ability to predict scan results and training level. Despite the overall correlation between prediction of CT abnormality and eventual findings, the subgroups of patients with seizure (Figure 4) and trauma (Figure 5) did not show similar correlations. The exact reason for this is uncertain. It may be a function of the size of these subgroups, but we believe this is unlikely. In the trauma group, all acutely abnormal studies, except one infarction, had predictions of abnormality in the remote or low likelihood categories. In the patients with seizure, all the cases except one subdural hematoma had clinical predictions of CT abnormality, at least in the moderate range. Thus, although we could show no correlation between prediction and actual result for the seizure group, it appears that there was a higher clinical suspicion of which patients would actually have an abnormal CT in this group than in the trauma group. Clinical predictions of the type of pathology matched actual results 66.7% of the time. That the abnormality seen on CT was different than expected one-third of the time suggests that it is often difficult to identify the underlying pathology causing the patientg clinical complaint. CONCLUSION
Although our data show a definite relationship between prediction of CT abnormality and actual CT result, it clearly is not adequately refined to allow patient selection for CT based solely on clinical impression. Previous studies have argued for the use of various algorithms to guide clinicians in choosing patients for CT. 11-13,15.16 Others have suggested the liberal use of CT in ED patients with even minimal head trauma. 4-8'14 To date, no study has been able to show perfect sensitivity for the selection of patients with intracranial abnormalities without performance of a large proportion of negative examinations. Although it is clear that a large number of negative scans are being performed at a great financial cost, our current data do not provide an alternative to a low threshold for CT to avoid missing clinically silent but potentially lethal pathology. REFERENCES 1. Sexton CO, Caples C: EmergencyCT of the head: Indications and utilization. MdMedJ 1987;36:493-495.
1277
C R A N I A L CT Reinus & Zwemer
2. Mills ML, RussoLS, Ross BA: High-yield criteria for urgent cranial computed tomography scans. Ann EmergMed 1986;15:1167-1172. 3. Harrup SN: Head scanning during admission through the accident and emergency department. Injury1983;14:465-470. 4. Livingston DH, Loder PA, Kozinl J, et al: The use of CT scanning to triage patients requiring admission following minimal head injury. J Trauma1991;31:483-489. 5. Stein SC, RossSE: The value of computed tomographic scans in patients with low-risk head injuries. Neurosurgery1990;26:538-640. 6. FeuermanT, Ashley P, Gade FG, at al: Value of skull radiography, head computed tomographic scanning and admission for observation in cases of minor head injury. Neurosurgery 1988;22:449-453.
C o p y r i g h t 9 by t h e A m e r i c a n College o f E m e r g e n c y P h y s i c i a n s R e p r i n t no. 47/1/55407 Address for reprints: William R Reinus, MD Associate Professor Jewish Hospital Maltinckrodt Institute of Radiology Washington University Medical Center
7. Dacey RG Jr, Alves WM, Rimel RW, et al: Neurosurgical complications after apparently minor head injury. J Neurosurg1986;65:203-210.
215 S Kingshighway
8. Harad IT, Kerstein MD: Inadequacyof bedside clinical indicators in identifying significant intracranial injury in trauma patients. J Trauma1992;32:359-363.
314-454-7400
9. McMicken DB: EmergencyCT head scans in traumatic and atraumatic conditions. Ann Emerg Med1986;15:274-279.
St Louis, Missouri 53110
Fax 314454-5262
10. Wood LP, Parisi M, Finch IJ: Value of contrast enhanced CT scanning in the non-trauma emergencyroom patient. Neuroradiology1990;32:261-264. 11. Ramirez-LassepasM, Cipolle RJ, Morillo LR, et al: Value of computed tomographic scan in the evaluation of adult patients after their first seizure. Ann Neuro11984;15:536-543. 12. Young AC, Mohr PD, Borg CostanziJ, et al: is routine computerised axial tomography in epilepsy worth while? Lancet1982;2:1446-1447. 13. van Donselaar CA, Geerts AT, SchimsheimerR: Idiopathic first seizure in adult life: Who should be treated? BMJ 1991;302:620-623. 14. Livingston DH, Loder PA, Hunt CD: Minimal head injury: Is admission necessary?Am Surg 1991;57:14-17. 15. Vydareny K, Harle T, Potchen EJ: An algorithmic approach to the roentgenographicevaluation of head trauma: Medical and financial implications. InvestRadio11983;4:390-395. 16. French BN, Dublin AB: The value of computerizedtomography in the management of 1000 consecutive heed injuries, SurgNeurol1977;7:171-183. 17. Eisner RF,Turnbull TL, Howes DS, et al: Efficacy of "standard"seizure workup in the emergencydepartment. Ann EmergMed 1986;15:33-39. 18. RussoLS, Goldstein KH: CT evaluation in patients after first seizure. Ann Neuro11985;17:618619. 19. KnausWA, Wagner DP, Davis DO: CT for headache:Cost/benefit for subarachnoid hemorrhage.Am J Radiol1981;136:537-542. 20. GrosskreutzSR, OsbornRE, SanchezRM: Computedtomography of the brain in the evaluation of the headachepatient. Milit Med 1991;156:137-I48. 21. Baker HL Jr: Cranial CT in the investigation of headache:Cost-effectivenessfor brain tumors J Neuroradio11983;10:112-116. 22. Adams RD, Victor M: Principlesof Neurology,ed 4. New York, McGraw-Hill, 1989. 23. Swets JA, Pickett RM: Evaluationof DiagnosticSystems:MethodsFromSignalDetection Theory.New York, Academic Press,1982. 24. Adams HP, Kassell NF, Torner JC, et al: CT and clinical correlations in recent aneurysmal subaraohnoidhemorrhage:A preliminary report of the CooperativeAneurysm Study. Neurology 1983;33:981-988.
1 27 8
ANNALS OF EMERGENCY MEDICINE
23:6
JUNE 1994