Pretest Probability Of Pulmonary Embolism Research Articles

Probability Scores and Diagnostic Algorithms in Pulmonary Embolism: Are They Followed in Clinical Practice?

IntroductionClinical probability scores (CPS) determine the pre-test probability of pulmonary embolism (PE) and assess the need for the tests required in these patients. Our objective is to investigate if PE is diagnosed according to clinical practice guidelines. Materials and methodsRetrospective study of clinically suspected PE in the emergency department between January 2010 and December 2012. A D-dimer value ≥500ng/ml was considered positive. PE was diagnosed on the basis of the multislice computed tomography angiography and, to a lesser extent, with other imaging techniques. The CPS used was the revised Geneva scoring system. ResultsThere were 3924 cases of suspected PE (56% female). Diagnosis was determined in 360 patients (9.2%) and the incidence was 30.6 cases per 100000 inhabitants/year. Sensitivity and the negative predictive value of the D-dimer test were 98.7% and 99.2% respectively. CPS was calculated in only 24 cases (0.6%) and diagnostic algorithms were not followed in 2125 patients (54.2%): in 682 (17.4%) because clinical probability could not be estimated and in 482 (37.6%), 852 (46.4%) and 109 (87.9%) with low, intermediate and high clinical probability, respectively, because the diagnostic algorithms for these probabilities were not applied. ConclusionsCPS are rarely calculated in the diagnosis of PE and the diagnostic algorithm is rarely used in clinical practice. This may result in procedures with potential significant side effects being unnecessarily performed or a high risk of underdiagnosis.

Escalas de probabilidad clínica y algoritmo diagnóstico en la embolia pulmonar: ¿se siguen en la práctica clínica?

IntroductionClinical probability scores (CPS) determine the pre-test probability of pulmonary embolism (PE) and assess the need for the tests required in these patients. Our objective is to investigate if PE is diagnosed according to clinical practice guidelines. Materials and methodsRetrospective study of clinically suspected PE in the emergency department between January 2010 and December 2012. A D-dimer value≥500 ng/ml was considered positive. PE was diagnosed on the basis of the multislice computed tomography angiography and, to a lesser extent, with other imaging techniques. The CPS used was the revised Geneva scoring system. ResultsThere was 3,924 cases of suspected PE (56% female). Diagnosis was determined in 360 patients (9.2%) and the incidence was 30.6 cases per 100,000 inhabitants/year. Sensitivity and the negative predictive value of the D-dimer test were 98.7% and 99.2% respectively. CPS was calculated in only 24 cases (0.6%) and diagnostic algorithms were not followed in 2,125 patients (54.2%): in 682 (17.4%) because clinical probability could not be estimated and in 482 (37.6%), 852 (46.4%) and 109 (87.9%) with low, intermediate and high clinical probability, respectively, because the diagnostic algorithms for these probabilities were not applied. ConclusionsCPS are rarely calculated in the diagnosis of PE and the diagnostic algorithm is rarely used in clinical practice. This may result in procedures with potential significant side effects being unnecessarily performed or to a high risk of underdiagnosis.

Patient preferences for testing for pulmonary embolism in the ED using a shared decision-making model

IntroductionShared decision making (SDM) is a process whereby patients and clinicians work together to make informed medical decisions that incorporate patient values. Recent data suggest that, for patients with low pretest probability of pulmonary embolism (PE), doubling the standard d-dimer cutoff may reduce the need for imaging with minimal increase in missed PE diagnoses. We used an SDM approach to determine patient preferences regarding this diagnostic approach. MethodsWe prospectively enrolled a consecutive sample of emergency department (ED) patients presenting with chest pain or dyspnea. We provided patients with a standardized description of the diagnostic workup for PE. We also provided image arrays describing the risks of computed tomography in low pretest probability patients and the risks of deferring imaging assuming a d-dimer was less than twice the value normally considered positive. We surveyed patients for their preference to undergo or defer imaging in this scenario. ResultsWe enrolled 203 ED patients. Mean age was 55 ± 17 years, and 61% were male. Seventy-four patients (37%) elected to defer computed tomography of the pulmonary arteries testing. Patients with a previous PE diagnosis were less likely to defer computed tomography of the pulmonary arteries testing (P = .007). There was no association between the decision to defer testing and age, sex, family history of PE, or self-assessed risk-taking tendency. ConclusionsWhen presented with a hypothetical scenario, more than one-third of patients deferred imaging for PE based on low clinical probability and a d-dimer less than twice the normal threshold. An SDM approach is acceptable to patients and may decrease imaging for PE.

Scores und Stadien in der Pneumologie

Useful scales and classifications for patients with pulmonary diseases are discussed. The modified Medical Research Council breathlessness scale (mMRC) is a measure of disability in lung patients. The GOLD classifications, the COPD-Assessment Test (CAT) and the BODE Index are important to classify the severity of COPD and to measure the disability of these patients. The Geneva score is a clinical prediction rule used in determining the pre-test probability of pulmonary embolism. The Pulmonary Embolism Severity Index (PESI) is a scoring system used to predict 30 day mortality in patients with pulmonary embolism. The Epworth Sleepiness Scale is intended to measure daytime sleepiness in patients with sleep apnea syndrome. The Asthma Controll Test (ACT) determines if asthma symptoms are well controlled.

Prediction Scores Do Not Correlate with Clinically Adjudicated Categories of Pulmonary Embolism in Critically Ill Patients

Prediction scores for pretest probability of pulmonary embolism (PE) validated in outpatient settings are occasionally used in the intensive care unit (ICU). To evaluate the correlation of Geneva and Wells scores with adjudicated categories of PE in ICU patients. In a randomized trial of thromboprophylaxis, patients with suspected PE were adjudicated as possible, probable or definite PE. Data were then retrospectively abstracted for the Geneva Diagnostic PE score, Wells, Modified Wells and Simplified Wells Diagnostic scores. The chance-corrected agreement between adjudicated categories and each score was calculated. ANOVA was used to compare values across the three adjudicated PE categories. Among 70 patients with suspected PE, agreement was poor between adjudicated categories and Geneva pretest probabilities (kappa=0.01 [95% CI -0.0643 to 0.0941]) or Wells pretest probabilities (kappa=-0.03 [95% CI -0.1462 to 0.0914]). Among four possible, 16 probable and 50 definite PEs, there were no significant differences in Geneva scores (possible = 4.0, probable = 4.7, definite = 4.5; P=0.90), Wells scores (possible = 2.8, probable = 4.9, definite = 4.1; P=0.37), Modified Wells (possible = 2.0, probable = 3.4, definite = 2.9; P=0.34) or Simplified Wells (possible = 1.8, probable = 2.8, definite = 2.4; P=0.30). Pretest probability scores developed outside the ICU do not correlate with adjudicated PE categories in critically ill patients. Research is needed to develop prediction scores for this population.

Right Ventricular Dilatation on Bedside Echocardiography Performed by Emergency Physicians Aids in the Diagnosis of Pulmonary Embolism

The objective of this study was to determine the diagnostic performance of right ventricular dilatation identified by emergency physicians on bedside echocardiography in patients with a suspected or confirmed pulmonary embolism. The secondary objective included an exploratory analysis of the predictive value of a subgroup of findings associated with advanced right ventricular dysfunction (right ventricular hypokinesis, paradoxical septal motion, McConnell's sign). This was a prospective observational study using a convenience sample of patients with suspected (moderate to high pretest probability) or confirmed pulmonary embolism. Participants had bedside echocardiography evaluating for right ventricular dilatation (defined as right ventricular to left ventricular ratio greater than 1:1) and right ventricular dysfunction (right ventricular hypokinesis, paradoxical septal motion, or McConnell's sign). The patient's medical records were reviewed for the final reading on all imaging, disposition, hospital length of stay, 30-day inhospital mortality, and discharge diagnosis. Thirty of 146 patients had a pulmonary embolism. Right ventricular dilatation on echocardiography had a sensitivity of 50% (95% confidence interval [CI] 32% to 68%), a specificity of 98% (95% CI 95% to 100%), a positive predictive value of 88% (95% CI 66% to 100%), and a negative predictive value of 88% (95% CI 83% to 94%). Positive and negative likelihood ratios were determined to be 29 (95% CI 6.1% to 64%) and 0.51 (95% CI 0.4% to 0.7%), respectively. Ten of 11 patients with right ventricular hypokinesis had a pulmonary embolism. All 6 patients with McConnell's sign and all 8 patients with paradoxical septal motion had a diagnosis of pulmonary embolism. There was a 96% observed agreement between coinvestigators and principal investigator interpretation of images obtained and recorded. Right ventricular dilatation and right ventricular dysfunction identified on emergency physician performed echocardiography were found to be highly specific for pulmonary embolism but had poor sensitivity. Bedside echocardiography is a useful tool that can be incorporated into the algorithm of patients with a moderate to high pretest probability of pulmonary embolism.

Triple Rule Out: Why It Is Not Ready to Roll Out

Triple Rule Out: Why It Is Not Ready to Roll Out

Prognostic value of the Geneva prediction rule in patients with pulmonary embolism

BackgroundAssessment of pre-test probability of pulmonary embolism (PE) and prognostic stratification are two widely recommended steps in the management of patients with suspected PE. Some items of the Geneva prediction rule may have a prognostic value.We analyzed whether the initial probability assessed by the Geneva rule was associated with the outcome of patients with PE. MethodsIn a post-hoc analysis of a multicenter trial including 1,693 patients with suspected PE, the all-cause death or readmission rates during the 3-month follow-up of patients with confirmed PE were analyzed. PE probability group was prospectively assessed by the revised Geneva score (RGS). Similar analyses were made with the a posteriori-calculated simplified Geneva score (SGS). ResultsPE was confirmed in 357 patients and 21 (5.9%) died during the 3-month follow-up. The mortality rate differed significantly with the initial RGS group, as with the SGS group. For the RGS, the mortality increased from 0% (95% Confidence Interval: [0–5.4%]) in the low-probability group to 14.3% (95% CI: [6.3-28.2%]) in the high-probability group, and for the SGS, from 0% (95% CI: [0–5.4%] to 17.9% (95% CI: [7.4-36%]). Readmission occurred in 58 out of the 352 patients with complete information on readmission (16.5%). No significant change of readmission rate was found among the RGS or SGS groups. ConclusionsReturning to the initial PE probability evaluation may help clinicians predict 3-month mortality in patients with confirmed PE.(ClinicalTrials.gov: NCT00117169)

CT pulmonary angiography: an over-utilized imaging modality in hospitalized patients with suspected pulmonary embolism

AimsTo determine if computed tomographic pulmonary angiography (CTPA) was overemployed in the evaluation of hospitalized patients with suspected acute pulmonary embolism (PE).MethodsData were gathered retrospectively on hospitalized patients (n=185) who had CTPA for suspected PE between June and August 2009 at our institution.ResultsCTPA was done in 185 hospitalized patients to diagnose acute PE based on clinical suspicion. Of these, 30 (16.2%) patients were tested positive for acute PE on CTPA. The Well's pretest probability for PE was low, moderate, and high in 77 (41.6%), 83 (44.9%), and 25 (13.5%) patients, respectively. Out of the 30 PE-positive patients, pretest probability was low in 2 (6.6%), moderate in 20 (66.7%), and high in 8 (26.6%) (p=0.003). Modified Well's criteria applied to all patients in our study revealed 113 (61%) with low and 72 (39%) with high clinical pretest probability. When modified Well's criteria was applied to 30 PE-positive patients, 10 (33.3%) and 20 (66.6%) were found to have low and high pretest probability, respectively (p=0.006). D-dimer assay was done in 30 (16.2%) of the inpatients with suspected PE and all of them were found to have elevated levels. A lower extremity duplex ultrasound confirmed deep venous thrombosis in 17 (9.1%) of the patients with suspected PE, at least 1 week prior to having CTPA.ConclusionUnderstanding the recommended guidelines, evidence-based literature, and current concepts in evaluation of patients with suspected acute PE will reduce unnecessary CTPA examinations.

365 Contribution and comparison of the wells score with the Geneva score and revised Geneva score for assessing pretest probability of pulmonary embolism in emergency department: Tunisian experience

365 Contribution and comparison of the wells score with the Geneva score and revised Geneva score for assessing pretest probability of pulmonary embolism in emergency department: Tunisian experience

377 Right Ventricular Strain on Bedside Echocardiography: Does It Help in the Diagnosis of a Pulmonary Embolism?

377 Right Ventricular Strain on Bedside Echocardiography: Does It Help in the Diagnosis of a Pulmonary Embolism?

The value of 64-detector row computed tomography for the exclusion of pulmonary embolism

Recently, a diagnostic strategy using a clinical decision rule, D-dimer testing and spiral computed tomography (CT) was found to be effective in the evaluation of patients with clinically suspected pulmonary embolism (PE). However, the rate of venous thromboembolic complications in the three-month follow-up of patients with negative CT was still substantial and included fatal events. It was the objective to evaluate the safety of withholding anticoagulants after a normal 64-detector row CT (64-DCT) scan from a cohort of patients with suspected PE. A total of 545 consecutive patients with clinically suspected first episode of PE and either likely pre-test probability of PE (using the simplified Wells score) or unlikely pre-test probability in combination with a positive D-dimer underwent a 64-DCT. 64-DCT scanning was inconclusive in nine patients (1.6%), confirmed the presence of PE in 169 (31%), and ruled out the diagnosis in the remaining 367. During the three-month follow-up of the 367 patients one developed symptomatic distal deep-vein thrombosis (0.27%; 95%CI, 0.0 to 1.51%) and none developed PE (0 %; 95%CI, 0 to 1.0%). We conclude that 64-DCT scanning has the potential to safely exclude the presence of PE virtually in all patients presenting with clinical suspicion of this clinical disorder.

Acute Pulmonary Embolism Detected by Perfusion SPECT/CT Masquerading as an Intermediate Probability Planar V/Q Scan

A 51-year-old man with renal cell carcinoma, renal insufficiency, and a remote pulmonary embolism (PE) was referred for a ventilation-perfusion (V/Q) scan because of dyspnea and chest pain one day after left partial nephrectomy. Planar V/Q scan revealed an intermediate probability for PE. As the pretest probability for PE was high, a perfusion SPECT/CT was obtained, which clearly demonstrated a large segmental perfusion defect on a background of clear lung parenchyma, consistent with the presence of PE. Follow-up planar V/Q scan after 1 month of anticoagulation therapy was normal.

Comparison of the Wells score with the simplified revised Geneva score for assessing pretest probability of pulmonary embolism

Introduction The Wells score is widely used in the assessment of pretest probability of pulmonary embolism (PE). The revised Geneva score is a fully standardized clinical decision rule that was recently validated and further simplified. We compared the predictive accuracy of these two scores. Methods Data from 339 patients clinically suspected of PE from two prospective management studies were used and combined. Pretest probability of PE was assessed prospectively by the Wells score. The simplified revised (SR) Geneva score was calculated retrospectively. The predictive accuracy of both scores was compared by area under the curve (AUC) of receiver operating characteristic (ROC) curves. Results The overall prevalence of PE was 19%. Prevalence of PE in the low, moderate and high pretest probability groups assessed by the Wells score and by the simplified revised Geneva score was respectively 2%(95% CI (CI) 1-6) and 4% (CI 2-10), 28% (CI 22-35) and 25% (CI 20-32), 93% (CI 70-99) and 56% (CI 27-81). The Wells score performed better than the simplified revised Geneva score in patients with a high suspicion of PE (p < 0.05). The AUC for the Wells score and the simplified revised Geneva score was 0.85 (CI: 0.81 to 0.89) and 0.76 (CI: 0.71 to 0.80) respectively. The difference between the AUCs was statistically significant (p = 0.005). Conclusions In our population the Wells score appeared to be more accurate than the simplified revised Geneva score. The impact of this finding in terms of patient outcomes should be investigated in a prospective study.

Improving diagnostics of pulmonary embolism with clinical prediction models in a clinic of pulmonary diseases

Purpose of the Study: Clinical prediction models have been developed to assess the pre-test probability for pulmonary embolism (PE). The Wells model and the revised Geneva score are the two most well studied. Our purpose was to compare the two prediction models, and indentify the frequent clinical findings of PE in patients admitted to the University Clinic of Pulmonary and Allergic Diseases Golnik. Methods: In 100 random emergency department patients and hospital inpatients with suspected PE and performed pulmonary CT angiography (CTPA) as the gold standard, a retrospective assessment of the clinical probability of PE by the Wells rule and the revised Geneva score was made. ECG, D-dimer, NT-proBNP, arterial blood gas analysis, chest X-ray, CTPA and 13 other clinical findings were analysed as well. Results: Average age was 65 years (SD 14.5), 39 % were male. The overall prevalence of PE was 33 %. The rates of PE in low, moderate, and high PE risk groups as determined according to the Wells model and the revised Geneva score were 3.7, 53,1, 100, and 14.3, 32.1, 83.3 %, respectively. ROC analysis showed that the Wells model was statistically more accurate than the Geneva score with the area under the curve (AUC) in Wells model 0.85 (95 % CI 0.762–0.936) and in Geneva score 0.73 (95 % CI 0.612–0.838). Sudden dyspnea, active malignancy, venous thromboembolism (VTE) history, estrogen therapy, deep vein thrombosis (DVT) signs, ECG changes and lower PaCO2 were significantly more frequent in PE group. All patients with PE had an increased concentration of D-dimer, and no PE were diagnosed in the group of patients with normal D-dimer. CTPA was ordered in 17 % of patients with low pre-test probability of PE according to Wells criteria and normal D-dimer. Conclusions: The Wells model is more accurate than the Geneva scoring system for the diagnosis of PE in patients admitted to a pulmonary clinic. Additional findings, such as sudden dyspnea, estrogen therapy, ECG changes and lower PaCO2, should always be incorporated in clinical assessment of PE. Adding the Wells algorithm to the clinical pathway for PE management might slightly decrease the number of CTPA.

Pulmonary Embolism at CT Angiography: Implications for Appropriateness, Cost, and Radiation Exposure in 2003 Patients

To determine whether thromboembolic risk factor assessment could accurately indicate the pretest probability for pulmonary embolism (PE), and if so, computed tomographic (CT) angiography might be targeted more appropriately than in current usage, resulting in decreased costs and radiation exposure. Institutional review board approval was obtained. Electronic medical records of 2003 patients who underwent CT angiography for possible PE during 1(1/2) years (July 2004 to February 2006) were reviewed retrospectively for thromboembolic risk factors. Risk factors that were assessed included immobilization, malignancy, hypercoagulable state, excess estrogen state, a history of venous thromboembolism, age, and sex. Logistic regressions were conducted to test the significance of each risk factor. Overall, CT angiograms were negative for PE in 1806 (90.16%) of 2003 patients. CT angiograms were positive for PE in 197 (9.84%) of 2003 patients; 6.36% were Emergency Department patients, and 13.46% were inpatients. Of the 197 patients with CT angiograms positive for PE, 192 (97.46%) had one or more risk factors, of which age of 65 years or older (69.04%) was the most common. Of the 1806 patients with CT angiograms negative for PE, 520 (28.79%) had no risk factors. The sensitivity and negative predictive value of risk factor assessment in all patients were 97.46% and 99.05%, respectively. All risk factors, except sex, were significant in the multivariate logistic regression (P < .031). In the setting of no risk factors, it is extraordinarily unlikely (0.95% chance) to have a CT angiogram positive for PE. This selectivity and triage step should help reduce current costs and radiation exposure to patients.

12-Lead ECG Findings of Pulmonary Hypertension Occur More Frequently in Emergency Department Patients With Pulmonary Embolism Than in Patients Without Pulmonary Embolism

Acute pulmonary embolism can produce abnormalities on ECG that reflect severity of pulmonary hypertension. Early recognition of these findings may alter the estimated pretest probability of pulmonary embolism and prompt more aggressive treatment before hemodynamic instability ensues, but it is first important to test whether these findings are specific to patients with pulmonary embolism. We hypothesize that ECG findings consistent with pulmonary hypertension would be observed more frequently in patients with pulmonary embolism. Secondary analysis of a prospective, observational cohort of emergency department patients who were tested for pulmonary embolism. ECGs were ordered at clinician's discretion and interpreted at presentation. Six thousand forty-nine patients had an ECG, 354 (5.9%) of whom were diagnosed with pulmonary embolism. The frequency, positive likelihood ratio (LR+) and 95% confidence interval (CI) of each predictor were as follows: S1Q3T3 8.5% with pulmonary embolism versus 3.3% without pulmonary embolism (LR+ 3.7; 95% CI 2.5 to 5.4); nonsinus rhythm, 23.5% versus 16.6% (LR+ 1.4; 95% CI 1.2 to 1.7); inverted T waves in V1 to V2, 14.4% versus 8.1% (LR+ 1.8; 95% CI 1.3 to 2.3); inversion in V1 to V3, 10.5% versus 4.0% (LR+ 2.6; 95% CI 1.9 to 3.6); inversion in V1 to V4, 7.3% versus 2.0% (LR+ 3.7; 95% CI 2.4 to 5.5); incomplete right bundle branch block, 4.8% versus 2.8% (LR+ 1.7; 95% CI 1.0 to 2.7); tachycardia (pulse rate >100 beats/min), 28.8% versus 15.7% (LR+ 1.8; 95% CI 1.5 to 2.2). Likelihood ratios and specificities were similar when patients with previous cardiopulmonary disease were excluded from analysis. Findings of acute pulmonary hypertension were infrequent overall but were observed more frequently in patients with the final diagnosis of pulmonary embolism compared with patients who do not have pulmonary embolism.

Chronic Obstructive Pulmonary Disease in Patients With Acute Symptomatic Pulmonary Embolism

Background The diagnosis of pulmonary embolism (PE) is often complicated by the presence of chronic obstructive pulmonary disease (COPD). Some studies have suggested that patients with PE and concomitant COPD have a worse prognosis than patients without COPD. Patients and Methods Outpatients diagnosed with acute symptomatic PE at a university tertiary care hospital were prospectively included in the study. Clinical characteristics, time between onset of symptoms and diagnosis, and outcome were analyzed according to presence or absence of COPD. The primary endpoint was all-cause deaths at 3 months. Results Of 882 patients with a confirmed diagnosis of acute symptomatic PE, 8% (95% confidence interval [CI], 6%-9%) had COPD. Patients with COPD were significantly more likely to have a delay in diagnosis of more than 3 days and to have a low pretest probability of pulmonary embolism according to a standardized clinical score. The total number of deaths during 3 months of follow-up was 128 (14%; 95% CI, 12%-17%). Factors significantly associated with mortality from all causes were a history of cancer or immobilization, systolic blood pressure less than 100 mm Hg, and arterial oxyhemoglobin saturation less than 90%. COPD was significantly associated with PE-related death in the logistic regression analysis (relative risk, 2.2; 95% CI, 1.0-5.1). Conclusions Patients with COPD and PE more often have a lower pretest probability and a longer delay in diagnosis of PE. COPD is significantly associated with PE-related death in the 3 months following diagnosis.

Prevalence of Pulmonary Embolism in Acute Exacerbations of COPD

Nearly 30% of all exacerbations of COPD do not have a clear etiology. Although pulmonary embolism (PE) can exacerbate respiratory symptoms such as dyspnea and chest pain, and COPD patients are at a high risk for PE due to a variety of factors including limited mobility, inflammation, and comorbidities, the prevalence of PE during exacerbations is uncertain. A systematic review of the literature was performed to determine the reported prevalence of PE in acute exacerbations of COPD in patients who did and did not require hospitalization. The literature search was performed using MEDLINE, CINAHL, and EMBASE, and complemented by hand searches of bibliographies. Only cross-sectional or prospective studies that used CT scanning or pulmonary angiography for PE diagnosis were included. Of the 2,407 articles identified, 5 met the inclusion criteria (sample size, 550 patients). Overall, the prevalence of PE was 19.9% (95% confidence interval [CI], 6.7 to 33.0%; p = 0.014). In hospitalized patients, the prevalence was higher at 24.7% (95% CI, 17.9 to 31.4%; p = 0.001) than those who were evaluated in the emergency department (3.3%). Presenting symptoms and signs were similar between patients who did and did not have PE. One of four COPD patients who require hospitalization for an acute exacerbation may have PE. A diagnosis of PE should be considered in patients with exacerbation severe enough to warrant hospitalization, especially in those with an intermediate-to-high pretest probability of PE.

Apport de la clinique : faut-il utiliser un score ?

The determination of the clinical pretest probability using clinical prediction models is an important step in the assessment of patients with suspected pulmonary embolism (PE). It helps establish which test or sequence of tests can effectively corroborate or safely rule out PE. For example, it has been demonstrated that it is safe to withhold anticoagulant therapy in patients with negative d-dimer results and low pretest probability at initial presentation. Clinical probability will also increase the diagnostic yield of ventilation perfusion lung scan. Compared with clinical gestalt, clinical prediction rules provide a standardized and more reproducible estimate of a patient's probability of having a PE. Clinical prediction models combine aspects of the history and physical examination to categorize a patient's probability of having a disease. The models classify patients as having a low, moderate, or high likelihood of having PE. Clinical prediction models have been validated and are well established for the diagnosis of PE in symptomatic patients. They allow all physicians, whatever their expertise, to reliably determine the clinical pretest probability of PE, and thus safely manage their patients using diagnostic and therapeutic algorithms.