Pretest Probability Of Pulmonary Embolism Research Articles

CT Angiography in the Evaluation of Acute Pulmonary Embolus

The purpose of this study was to assess the appropriate use of CT angiography (CTA) in the diagnostic evaluation of acute pulmonary embolism (PE). We reviewed a total of 575 CT angiograms obtained to evaluate for PE at a large level 1 trauma teaching hospital from January 2004 through March 2005. Various clinical settings were used for 267 inpatient (46%), 258 emergency department (45%), and 50 outpatient (9%) studies. We excluded CTA performed for other reasons, repeated CTA, and patient records with incomplete clinical data. On the basis of chart review in which the investigators were blinded to final diagnoses, pretest probability of PE according to the Wells criteria was retrospectively assigned to each patient. D-dimer values, when obtained, also were reviewed. The diagnosis of PE was based on final CTA reports. PE was diagnosed in 9.57% of 575 patients. Positivity rates by location were 32 (12%) of the 267 inpatients, 22 (8.5%) of the 258 emergency department patients, and one (2.0%) of the 50 outpatients. Three (< 1%) of the 575 patients had high probability of PE, even though 351 patients had gone directly to CTA. Of the other 572 patients, 158 (28%) had intermediate and 414 (72%) low probability of PE. In the high, intermediate, and low probability groups, two (67%), 24 (15%), and 29 (7%), respectively, of the patients had PE. A D-dimer assay was performed for 224 (39%) of the 575 patients. Thirty-nine (17%) of the 224 patients had normal results (< 0.5 microg/mL); 107 (48%), intermediate results (0.6-2.0 microg/mL); and 78 (35%), abnormal results (> 2.0 microg/mL). In the emergency department cohort, 151 (59%) of 258 patients underwent a D-dimer assay. Thirty-two (21%) of the 151 patients had normal results; 81 (54%), intermediate results; and 38 (25%), abnormal results. Only one patient with a normal D-dimer level and three patients with intermediate D-dimer levels had PE, the equivalent of 3% of each group. The number of CTA examinations ordered for patients with normal and intermediate D-dimer results was 146 (25% of the 575 total studies). Twenty-two (8%) of the 258 emergency department patients had PE, and clinical suspicion of PE was high for 11 (50%), intermediate for 10 (45%), and low for one (5%) of those patients. Our data showed suboptimal use of the Wells criteria and subjective overestimation of the probability of PE before ordering of CTA. Although a definitive acceptable PE positivity rate for CTA has not been established, the 10% yield represents overuse of CTA as a screening rather than a diagnostic examination.

Pulmonary Embolism Outcome: A Prospective Evaluation of CT Pulmonary Angiographic Clot Burden Score and ECG Score

The purpose of this study was to establish whether a correlation exists between the CT pulmonary angiographic clot burden score, the ECG score at diagnosis, and the 12-month mortality rate among patients diagnosed with pulmonary embolism. A total of 523 consecutive patients who underwent CT pulmonary angiography for a suspected moderate to high pretest probability of pulmonary embolism were recruited from March 2003 to October 2004. There were 105 patients with positive CT pulmonary angiography examinations. Two consultant respiratory physicians and two consultant radiologists independently and prospectively calculated an ECG score and a quantified pulmonary artery clot burden, respectively. Twelve-month follow-up was completed in all patients. The mean ECG score was 2.36 (SD, 2.84) and the mean clot burden score percentage was 23.74% (16.8%). Poor correlation (r = 0.09) was seen between the average ECG score and the average clot burden score percentage (p = 0.39) at diagnosis. Thirteen patients had died at the 12-month follow-up. The mean ECG score for those patients who were alive was 2.4 (2.91) and for those who had died was 2.03 (2.34) at 12 months (p = 0.65). The mean clot burden score percentage for those patients who were alive was 24% (17%) and for those who had died was 22.1% (15.7%) at 12 months (p < 0.73). No statistically significant association was seen between ECG score and CT pulmonary angiographic clot burden at diagnosis and the 12-month all-cause mortality rate of patients diagnosed with pulmonary embolism.

La perfusion pulmonaire en morphoTEMP dans le diagnostic de l’embolie pulmonaire : comparaison à la scintigraphie pulmonaire planaire de ventilation/perfusion

The aim of this study is to assess a new tool for the diagnosis of acute pulmonary embolism (PE): single-photon emission computed tomography lung perfusion imaging associated with unenhanced computed tomography (SPECT/CT) compared to planar ventilation-perfusion (VQ) lung scintigraphy. Methods One hundred and three patients with suspected acute PE underwent VQ scintigraphy (two scans were uninterpretable) followed by perfusion SPECT/CT. The two types of images were analysed separately: (1) according to the modified PIOPED scintigraphic criteria for VQ lung scan and (2) with regard to SPECT/CT mismatches suggestive acute PE (segmental perfusion defects detected on SPECT images not matched with CT abnormalities). Results On average, the number of segmental perfusion defects per patient was higher with SPECT/CT than with planar scintigraphy (4.3 ± 3.6 versus 2.8 ± 2.6; p < 0.001). A mismatch was found with SPECT-CT in 0% (0/18) of normal scintigraphy, and 8% (3/39) for low, 32% (8/25) for intermediate and 74% (14/19) for high probabilities of PE at scintigraphy. The presence of a SPECT/CT mismatch was also associated with higher pretest probability of acute PE ( p = 0.001), even for the 25 patients in the intermediate-probability subgroup ( p = 0.02). Finally, a SPECT/CT match was found in 29 patients that was not suggestive of acute PE due to the presence, in areas with perfusion defects on SPECT images, of the following CT abnormalities: hypodensity and/or emphysema (71%), condensation or atelectasis (38%), pleural disease (7%), extrapulmonary structure (14%) and/or bronchial obstruction (7%). Conclusion In patients with suspected acute PE, the results obtained with pulmonary SPECT/CT images are consistent with those obtained with VQ scintigraphy and the pretest probability of PE. Further studies comparing SPECT/CT imaging with angiographic techniques are now required to evaluate more specifically the diagnostic value of this new tool.

Evidence-based Practice in Radiology: Steps 3 and 4—Appraise and Apply Diagnostic Radiology Literature

Several paradigms for evidence-based practice (EBP) exist. One model proposes that specialist academic centers should primarily construct valid guidelines for various topics in medicine (top-down model). An alternative model integrates "the best research evidence with clinical expertise and patient values" (bottom-up model). Whereas the former model inherently implies a central specialized process, the latter implies that practitioners working in nonspecialist centers can learn and implement a standardized set of tools with which to ask a question, search and appraise the literature, and then apply best current evidence in a local setting. This article focuses on appraising the literature and applying retrieved results and is part of a series on EBP in radiology. This article describes a clinical scenario in which a new respirologist at a hospital requests indirect computed tomographic (CT) venography as part of a work-up of a patient with a high pretest probability for pulmonary embolism and a positive d-dimer test result. Many controversies surround the technique of indirect CT venography, and difficult topics such as this are ideally suited to the tools of EBP. This article will describe how to approach such a scenario.

Assessment of pretest probability of pulmonary embolism in the emergency department by physicians in training using the Wells model

IntroductionAssessment of pretest probability should be the initial step in investigation of patients with suspected pulmonary embolism (PE). In teaching hospitals physicians in training are often the first physicians to evaluate patients. ObjectiveTo evaluate the accuracy of pretest probability assessment of PE by physicians in training using the Wells clinical model and to assess the safety of a diagnostic strategy including pretest probability assessment. Patients and methods291 consecutive outpatients with clinical suspicion of PE were categorized as having a low, moderate or high pretest probability of PE by physicians in training who could take supervising physicians' advice when they deemed necessary. Then, patients were managed according to a sequential diagnostic algorithm including D-dimer testing, lung scan, leg compression ultrasonography and helical computed tomography. Patients in whom PE was deemed absent were followed up for 3 months. Results34 patients (18%) had PE. Prevalence of PE in the low, moderate and high pretest probability groups categorized by physicians in training alone was 3% (95% confidence interval (CI): 1% to 9%), 31% (95% CI: 22% to 42%) and 100% (95% CI: 61% to 100%) respectively. One of the 152 untreated patients (0.7%, 95% CI: 0.1% to 3.6%) developed a thromboembolic event during the 3-month follow-up period. ConclusionPhysicians in training can use the Wells clinical model to determine pretest probability of PE. A diagnostic strategy including the use of this model by physicians in training with access to supervising physicians' advice appears to be safe.

Imaging pulmonary embolism in pregnancy: what is the most appropriate imaging protocol?

Pulmonary embolism is the leading cause of death in pregnancy. Despite the difficulties in clinical diagnosis and the concerns regarding radiation of the fetus, the British Thoracic Society guidelines for imaging pulmonary embolism do not specifically address the issue of imaging for pulmonary embolism in this group. This communication discusses the difficulties of diagnosis and imaging pulmonary embolism in pregnancy and proposes a suitable imaging protocol. Clinical exclusion of patients from further imaging is recommended if the patient has a low pre-test probability of pulmonary embolism and a normal d-dimer. It is advised that all remaining patients undergo bilateral leg Doppler assessment. If this test is positive, the patient should be treated for pulmonary embolism; if negative, all patients should be referred for CT pulmonary angiography. Ideally, informed consent should be obtained prior to CT scanning. All neonates exposed to iodinated contrast in utero should have their thyroid function tested in the first week of life due to the theoretical risk of contrast induced hypothyroidism.

The Contribution of the Subjective Component of the Canadian Pulmonary Embolism Score to the Overall Score in Emergency Department Patients

Clinicians frequently use their experience to determine the pretest probability of pulmonary embolism (PE), although scoring systems are promoted as being more reliable. The Canadian Pulmonary Embolism Score (CPES) combines six objective questions and one subjective question. The CPES has been validated and appears to be useful for risk-stratifying patients. However, research suggests that subjective gestalt performs similarly to the CPES, and the influence of the subjective question on the predictive value of the CPES is not clear. To determine the test characteristics of the CPES, its subjective question, and the degree to which the predictive value of the CPES is influenced by its individual questions. The authors performed a prospective observational study on a cohort of emergency department patients suspected of having PE. The authors compared patients' CPES results with the diagnosis of PE, calculated the test characteristics of the CPES, and determined the contribution of individual CPES questions to the score's overall predictive value. Of 607 patients, 61 (10%) had PE. Of low-risk patients (CPES < or =4), 5.54% (n = 449; 95% confidence interval [95% CI] = 3.64% to 8.11%) had PE. The sensitivity (59.0%; 95% CI = 47.4% to 69.8%) and the negative predictive value (94.4%; 95% CI = 92.8% to 95.9%) of the CPES were similar to the sensitivity (53.2%; 95% CI = 40.2% to 65.8%) and negative predictive value (93.5%; 95% CI = 90.7% to 95.5%) of the subjective question alone. In multivariable analysis, nearly all of the predictive value of the CPES was derived from the subjective question. The predictive value of the CPES appears to be derived primarily from its subjective component.

Comparison of the Unstructured Clinician Estimate of Pretest Probability for Pulmonary Embolism to the Canadian Score and the Charlotte Rule: A Prospective Observational Study

Clinical decision rules have been validated for estimation of pretest probability in patients with suspected pulmonary embolism (PE). However, many clinicians prefer to use clinical gestalt for this purpose. The authors compared the unstructured clinical estimate of pretest probability for PE with two clinical decision rules. This prospective, observational study was conducted from October 2001 to July 2004 at an urban academic emergency department with an annual census of 105,000. A total of 2,603 patients were enrolled; mean age (+/- SD) was 45 (+/- 16) years, and 70% were female. All patients were evaluated for PE using a previously published protocol, including D-dimer and alveolar dead space measurements, and selected use of pulmonary vascular imaging. All had 45-day follow-up. Interobserver agreement for each pretest probability estimation method was measured in a separate group of 154 patients. The overall prevalence of PE was 5.8% (95% confidence interval [CI] = 4.9% to 6.8%). Most were deemed low risk for PE, including 69% by the unstructured estimate < 15%, 73% by the Canadian score < 2, and 88% by the Charlotte rule "safe." The corresponding prevalence of disease in each of these low-risk groups was 2.6%, 3.0%, and 4.2%. Weighted Cohen's kappa values were 0.60 (95% CI = 0.46 to 0.74) for the unstructured clinical estimate < 15%, 0.47 (95% CI = 0.33 to 0.61) for the Canadian score < 2, and 0.85 (95% CI = 0.69 to 1.0) for the Charlotte rule "safe." The unstructured clinical estimate of low pretest probability for PE compares favorably with the Canadian score and the Charlotte rule. Interobserver agreement for the unstructured estimate is moderate.

Comparison of the Unstructured Clinician Estimate of Pretest Probability for Pulmonary Embolism to the Canadian Score and the Charlotte Rule: A Prospective Observational Study

Comparison of the Unstructured Clinician Estimate of Pretest Probability for Pulmonary Embolism to the Canadian Score and the Charlotte Rule: A Prospective Observational Study

Comparison of Two Models of Attribute Matching to Predict Pretest Probability of Pulmonary Embolism

Comparison of Two Models of Attribute Matching to Predict Pretest Probability of Pulmonary Embolism

Comparison of 3 Clinical Models for Predicting the Probability of Pulmonary Embolism

Two clinical models have been described to predict the probability of pulmonary embolism: the Canadian (or Wells) model, and the Geneva model. A third model has been developed recently at our institution (the Pisa model). We compared the performance of the 3 models in 215 consecutive patients with suspected pulmonary embolism. The clinical probability predicted by the models was categorized as low, intermediate, or high. In all patients, pulmonary angiography was used as the reference diagnostic standard. In patients with pulmonary embolism, the extent of pulmonary embolization was assessed on the lung scan as an index of disease severity. The prevalence of pulmonary embolism was 43.3%, and the median extent of pulmonary embolization at diagnosis was 39.8% (range, 4.5%-75.3%). The proportions of patients categorized as having low, intermediate, or high probability were, respectively: 12%, 60%, and 28%, for the Geneva model; 30%, 55%, and 15%, for the Wells model; 37%, 37%, and 26% for the Pisa model. The frequencies of pulmonary embolism in the low, intermediate, and high probability categories were, respectively: 50%, 39%, and 49% for the Geneva model; 12%, 54%, and 64% for the Wells model; 5%, 42%, and 98% for the Pisa model. Among patients with pulmonary embolism, there was a strong, positive relation between clinical probability predicted by the Pisa model and the extent of pulmonary embolization. The Pisa model proved more accurate than the 2 other models. It may be useful to physicians in defining precisely the pretest probability of pulmonary embolism.

Role of the 12-Lead Electrocardiogram in Diagnosing Pulmonary Embolism

We investigated the role of the standard 12-lead electrocardiogram (ECG) to improve the pretest probability of pulmonary embolism before performing computed tomographic (CT) pulmonary angiography. A retrospective chart analysis was performed on patients who underwent CT pulmonary angiography at a tertiary care hospital during a 30-month period. Comparison of 15 ECG parameters was made between those with CT pulmonary angiograms positive for pulmonary embolism and a matched control group with negative CT pulmonary angiograms. Data were analyzed by chi-squared tests and logistic regression. Sinus tachycardia (39% vs. 24%, P <0.01), an S1 Q3 T3 pattern (12% vs. 3%, P <0.01), atrial tachyarrhythmias (15% vs. 4%, P <0.005), a Q wave in lead III (40% vs. 26%, P <0.02), and a Q3 T3 pattern (8% vs. 1%, P <0.02) were the findings significantly associated with pulmonary embolism. We conclude that 1) standard 12-lead ECG findings can increase the pretest probability of pulmonary embolism before performing CT pulmonary angiography; and that 2) the ECG findings have relatively low likelihood ratios to have clinical use.

Pulmonary embolism in younger adults: Clinical presentation and comparison of two scoring systems used to estimate pretest probability of disease in the emergency department

Study objectives: Previous reports suggested that clinical presentation of pulmonary embolism could be different in younger compared with older patients. We test this hypothesis and compare 2 scoring systems used to estimate pretest probability of pulmonary embolism in younger and older patients admitted to the emergency department (ED). Methods: This is an observational retrospective study of 80 consecutive patients (40 younger adults, age ≤45 years; 40 older adults, age >45 years) admitted to the ED of an urban hospital from January 1996 to June 2003 for suspected pulmonary embolism, confirmed by high-probability lung scan or spiral computed tomography. We excluded patients with cardiopulmonary diseases. We collected data of history, age, sex, symptoms, signs and parameters, laboratory tests, chest radiograph, ECG, and arterial blood gas and estimated pretest probability of pulmonary embolism using Wells system according to 7 variables: suspected deep venous thrombosis, an alternative diagnosis is less likely than pulmonary embolism, pulse rate greater than 100 beats/min, recent immobilization or surgery, previous deep venous thrombosis/pulmonary embolism, hemoptysis, and malignancy; and Wicki system, based on 8 variables: recent surgery, previous thromboembolic event, older age, hypocapnia, hypoxemia, tachycardia, band atelectasis, or elevation hemidiaphragm on chest radiograph. A probability score was calculated by adding points assigned to these variables. We used Student's <i>t</i> or Fisher exact test to compare 2 groups. Spearman rank correlation coefficient was calculated for 2 score models and between each model and number of unperfused lung segments. Results: Mean ages were 39 years (range 25 to 45 years) for younger adults and 81 years (range 70 to 93 years) for older adults. After comparison with older patients, younger patients had less typical pulmonary embolism risk factors (in particular recent immobilization: 20% versus 35%, <i>P</i>=.03; malignancy: 6% versus 36%, <i>P</i><.001); less abnormal ECG (40% versus 70%, <i>P</i><.001) (right bundle-branch block was the more frequent abnormality in younger adults, 30% versus 17%, <i>P</i><.001); less abnormal radiograph (20% versus 40%, <i>P</i><.001); lower d-dimer levels (mean of 875, 8 μg/L versus 1,889, 7 μg/L in older adults [<i>P</i><.05]). Among younger adults, the more frequent symptoms were dyspnea (50%), chest pain (50% versus 30% in older adults, <i>P</i>=.006), cough (20% versus 5% in older adults, <i>P</i>=.003), and hemoptysis (15% versus 5%, <i>P</i><.03). At presentation, younger patients showed better parameters and better air room arterial blood gas (PaO₂, oxygen alveolar-arterial difference). The 2 predictive systems showed a different distribution of scores in 2 groups. Among older adults, with both systems, there was a predominance of high scores: 85% with Wells score greater than 2 (high pulmonary embolism probability) and 85% with Wicki score greater than 5 (high pulmonary embolism probability). Instead, among younger adults there was a high predominance of high score with Wells score: 90% with score greater than 2, but few younger adults had a Wicki score greater than 5 (45%). Between the 2 systems, there is a weak positive correlation (<i>r</i>=0.31, <i>P</i>>.05). The Wells system showed a moderate positive correlation with the number of unperfused lung segments (<i>r</i>=0.68, <i>P</i>=.004). Conclusion: In this study, among younger adults with pulmonary embolism, there is a more insidious clinical presentation; the Wells system has a predominance of high scores and seems to have a positive correlation with pulmonary embolism severity. The low number of patients is the main limitation of the study.

Clinical gestalt and the diagnosis of pulmonary embolism: Does experience matter?

Study objectives: We seek to determine whether the accuracy of pretest assessment of the likelihood of pulmonary embolism was related to physician experience. We compared the accuracy of the subjective pretest probability assessment made by senior physicians (postgraduate year [PGY]-4+) to that of interns (PGY-1) and residents (PGY-2 and PGY-3) working in the emergency department (ED) of a large teaching hospital. Methods: We performed a prospective observational study in an urban, academic ED with annual census of 48,000 patient visits. Eligible patients had at least 1 diagnostic test ordered to evaluate pulmonary embolism. The physician treating the patient was asked whether he or she considered pulmonary embolism the diagnosis or whether an alternative diagnosis was likely. This result was compared with the patient's ultimate diagnosis. Physicians' experience was categorized by the number of years of training since medical school graduation. Results: We enrolled 583 adults evaluated for pulmonary embolism in the ED. Pulmonary embolism was considered the most likely diagnosis for 26% of patients. Pulmonary embolism was diagnosed in 10% of patients. There was a trend toward increasing diagnostic accuracy with increasing experience, as demonstrated by the frequency of true positive assessments (17% versus 20% versus 25%), true negative assessments (89% versus 94% versus 96%), and likelihood ratio (1.49 versus 2.34 versus 3.33), respectively ( P for trend .1). However, when compared with validated clinical prediction rules, no rule was identified with a likelihood ratio between those of the inexperienced and experienced physicians in our study. Conclusion: Clinical experience appears to be related to the ability to accurately determine the pretest probability of pulmonary embolism. However, this difference is unlikely to be clinically significant. The difference in accuracy between inexperienced and experienced physicians is not sufficiently large to distinguish between the 2 when determining whether clinical gestalt or a clinical prediction rule should be used to determine the pretest probability of pulmonary embolism.

Review: clinical gestalt strategies and clinical prediction rules have similar discriminate pretest probabilities of pulmonary embolism

Chunilal SD, Eikelboom JW, Attia J, et al. Does this patient have pulmonary embolism? JAMA 2003;290:2849–58. [OpenUrl][1][CrossRef][2][PubMed][3][Web of Science][4] Q In patients with suspected pulmonary embolism, how do clinical prediction...

Clinical experience and pre-test probability scores in the diagnosis of pulmonary embolism.

The Geneva and Wells pre-test probability scores are intended to replace empirical assessment of patients with suspected pulmonary embolism (PE). The effect of clinical experience on the inter-rater variability of these scores, and on empirical judgement, is unknown. To determine whether medical staff appointment grade affects the inter-rater variability of these pre-test probability scores, or empirical assessment, in patients with suspected PE. Questionnaire survey. Doctors were grouped by grade (mean number of years since graduation+/-SEM): house officers 0.7+/-0.2, registrars 6.3+/-0.6, consultants 25+/-4 and applied pre-test probability scores to actual case scenarios. The Geneva score was the most consistent method of determining pre-test probability and was unaffected by clinical experience (Geneva kappa=0.73, Wells kappa=0.38, empirical kappa=0.23, p<0.001 ). With empirical judgement, inter-rater variability was inversely proportional to clinical experience (house officers kappa=0.37, registrars kappa=0.24, consultants kappa= 0.16, p<0.05). The Geneva score was the least variable method and can be applied by junior or senior doctors. Using empirical judgement, junior doctors were more likely to agree on the pre-test probability of PE than were their more senior colleagues. This may imply that as physicians gain experience, they recognize that the diagnosis of PE can be difficult to assess and are reluctant to exclude it on clinical grounds.

More Data on Spiral CT and Diagnosis of Pulmonary Embolism

Increasingly, spiral CT is incorporated into diagnostic strategies for pulmonary embolism (PE). In this multicenter French study, researchers examined outcomes with the following algorithm: All patients with suspected PE underwent clinical estimation of pretest probability of PE (using a published scheme), spiral CT, and leg ultrasound (US). Patients with negative CT and US and …

New methods for estimating pretest probability in the diagnosis of pulmonary embolism.

The clinical assessment of the probability of pulmonary embolism is a key step in proposed diagnostic strategies for pulmonary embolism, because the interpretation of noninvasive test results is conditional on the pretest probability derived from the presence or absence of clinical factors. The past year has brought important progress in the general area of clinical prediction of pulmonary embolism with the publication of two new simple clinical prediction rules. Each of the prediction rules includes a total of seven clinical variables that, when combined, allow for the categorization of patients into categories of low, intermediate, or high pretest probability of pulmonary embolism. Although these clinical prediction rules are perhaps only slightly better than the estimates of experienced clinicians, they provide an explicit method for estimating the probability of PE as an adjunct to diagnostic testing. Further validation work is now needed to assess how well these new prediction rules perform in settings other than the derivation sites.

Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer.

The limitations of the current diagnostic standard, ventilation-perfusion lung scanning, complicate the management of patients with suspected pulmonary embolism. We previously demonstrated that determining the pretest probability can assist with management and that the high negative predictive value of certain D -dimer assays may simplify the diagnostic process. To determine the safety of using a simple clinical model combined with D -dimer assay to manage patients presenting to the emergency department with suspected pulmonary embolism. Prospective cohort study. Emergency departments at four tertiary care hospitals in Canada. 930 consecutive patients with suspected pulmonary embolism. Physicians first used a clinical model to determine patients' pretest probability of pulmonary embolism and then performed a D -dimer test. Patients with low pretest probability and a negative D -dimer result had no further tests and were considered to have a diagnosis of pulmonary embolism excluded. All other patients underwent ventilation-perfusion lung scanning. If the scan was nondiagnostic, bilateral deep venous ultrasonography was done. Whether further testing (by serial ultrasonography or angiography) was done depended on the patients' pretest probability and the lung scanning results. Patients received a diagnosis of pulmonary embolism if they had a high-probability ventilation-perfusion scan, an abnormal result on ultrasonography or pulmonary angiography, or a venous thromboembolic event during follow-up. Patients for whom the diagnosis was considered excluded were followed up for 3 months for the development of thromboembolic events. The pretest probability of pulmonary embolism was low, moderate, and high in 527, 339, and 64 patients (1.3%, 16.2%, and 37.5% had pulmonary embolism), respectively. Of 849 patients in whom a diagnosis of pulmonary-embolism had initially been excluded, 5 (0.6% [95% CI, 0.2% to 1.4%]) developed pulmonary embolism or deep venous thrombosis during follow-up. However, 4 of these patients had not undergone the proper diagnostic testing protocol. In 7 of the patients who received a diagnosis of pulmonary embolism, the physician had performed more diagnostic tests than were called for by the algorithm. In 759 of the 849 patients in whom pulmonary embolism was not found on initial evaluation, the diagnostic protocol was followed correctly. Only 1 (0.1% [CI, 0.0% to 0.7%]) of these 759 patients developed thromboembolic events during follow-up. Of the 437 patients with a negative D -dimer result and low clinical probability, only 1 developed pulmonary embolism during follow-up; thus, the negative predictive value for the combined strategy of using the clinical model with D -dimer testing in these patients was 99.5% (CI, 99.1% to 100%). Managing patients for suspected pulmonary embolism on the basis of pretest probability and D -dimer result is safe and decreases the need for diagnostic imaging.

69. The accuracy of clinical diagnosis in defining the pre-test probability of pulmonary embolism

69. The accuracy of clinical diagnosis in defining the pre-test probability of pulmonary embolism