Diagnosis
Spiral computer tomography for the diagnosis of pulmonary embolism in critically ill surgical patients: A comparison with pulmonary angiography.
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This review may be
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Summary
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| Posted By: |
Gordon S. Doig |
| E-Mail: |
Gordon.Doig@EvidenceBased.net
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| Posted Date: |
14 Aug 2001 |
| Title: |
Spiral computer tomography for the diagnosis of pulmonary embolism in critically ill surgical patients: A comparison with pulmonary angiography. |
| Authors: |
Velmahos GC, Vassiliu P, Wilcox A et al |
| Reference: |
Arch Surg 2001;136:505-510 |
| Link: |
Click here for a direct link to the paper. A password may be required for access to fulltext.
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| Abstract: |
HYPOTHESIS: Spiral computed tomographic pulmonary angiography (CTPA) is sensitive and specific in diagnosing pulmonary embolism (PE) in critically ill surgical patients.
DESIGN: Prospective study comparing CTPA with the criterion standard, pulmonary angiography (PA).
SETTING: Surgical intensive care unit of an academic hospital.
PATIENTS: Twenty-two critically ill surgical patients with clinical suspicion of PE. The CTPAs and PAs were independently read by 4 radiologists (2 for each test) blinded to each other's interpretation. Clinical suspicion was classified as high, intermediate, or low according to predetermined criteria. All but 2 patients had marked pulmonary parenchymal disease at the time of the event that triggered evaluation for PE.
INTERVENTIONS: Computed tomographic pulmonary angiography and PA in 22 patients, venous duplex scan in 19.
RESULTS: Eleven patients (50%) had evidence of PE on PA, 5 in central and 6 in peripheral pulmonary arteries. The sensitivity and specificity of CTPA was, respectively, 45% and 82% for all PEs, 60% and 100% for central PEs, and 33% and 82% for peripheral PEs. Duplex scanning was 40% sensitive and 100% specific in diagnosing PE. The independent reviewers disagreed only in 14% of CTPA and 14% of PA interpretations. There were no differences in risk factors or clinical characteristics between patients with and without PE. The level of clinical suspicion was identical in the 2 groups.
CONCLUSIONS: Pulmonary angiography remains the gold standard for the diagnosis of PE in critically ill surgical patients. Computed tomographic pulmonary angiography needs further evaluation in this population. |
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Are the Results Valid?
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Was there an independent, blind comparison with a reference standard? |
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Yes. Pulmonary angiography was used as the reference standard and angiograms and CT images were read by different radiologists who were 'blind' to the results of each other's readings. |
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Did the patient sample include an appropriate spectrum of patients to whom the diagnostic test will be applied in clinical practice? |
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Yes. Fairly simple, objective criteria were used to select patients for inclusion. |
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Did the results of the test being evaluated influence the decision to perform the reference standard? |
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No. The results of the spiral CT did not influence the decision to perform an angiogram. All patients who entered the study received both a CT and an angio. |
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Were the methods for performing the test described in sufficient detail to permit replication? |
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Yes. The methods appear to be described in sufficient detail. |
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What are the Results?
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Are likelihood ratios for the test results presented or data necessary for their calculation provided? |
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Using the angiogram as the reference standard, the sensitivity of the spiral CT was reported as45% with a specificity of 82%. This yields a likelihood ratio of 2.5 for a positive test [sens/(1-spec) = .45/(1-.82)=2.5]. Unfortunately, since there were only 22 patients in this study, the confidence limits around the estimates of sensitivity and specificity are VERY wide. From the PIOPED study, the likelihood ratio for a positive 'high probability' V/Q scan is 18.3 with an 'intermediate' positive scan LRT of 1.2 and a 'low probability' scan of 0.36. |
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Will the Results Help Me In Caring For My Patients?
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Will the reproducibility of the test result and its interpretation be satisfactory in my setting? |
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Yes. There is no reason to belive the results obtained in any large tertiary care centre should differ from this paper's findings. |
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Are the results applicable to my patient? |
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Yes. The patients were fairly representative of Surgical ICU patients. |
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Will the results change my management? |
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Probably not. These findings do not demonstrate that spiral CT is more useful for screening PEs than V/Q scans. If you are currently using V/Q scans, this paper would not motivate a change to spiral CT. |
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Will patients be better off as a result of the test? |
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At the current level of performance (likelihood ratio for positive test = 2.5), spiral CT provides a 'small' (but potentially useful) improvement in information however, since there are both false positives and false negatives with spiral CTs, a significant number of patients with both negative and positive results would need to be Angio'd in order to be certain that therapy (anticoagulation) is appropriate. |
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Spiral computer tomography for the diagnosis of pulmonary embolism in critically ill surgical patients: A comparison with pulmonary angiography.
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