New diagnostic tests for pulmonary embolism

Role of echocardiography in a patient with suspected acute pulmonary embolism: a case report

Background

Approximately half of pulmonary embolism cases are diagnosed in an emergency context. The classic symptoms of pulmonary embolism are absent in intensive care unit patients who are under sedation and on mechanical ventilation. In this scenario, after the development of sudden, severe hypotension, pulmonary embolism must be considered and included in a differential diagnosis according to the cause of admission. Echocardiography may be of further help in a differential diagnosis of the cause of shock.

Case presentation

We present a case of a 44-year-old Caucasian man who was admitted to the intensive care unit with a diagnosis of community-acquired pneumonia and respiratory failure and who required invasive mechanical ventilation. During admission, the patient developed sudden, severe hypotension that was refractory to treatment. An adequate diagnosis with transthoracic echocardiography was unachievable because of a poor echocardiographic window. However, the combined use of electrocardiography and transesophageal echocardiography established pulmonary embolism as a high-probability diagnosis based on findings of right ventricular pressure overload and right ventricular dysfunction. The unfavorable hemodynamic situation of the patient prevented his transfer to carry out other complementary tests that could confirm the diagnosis of pulmonary embolism. Fibrinolytic and anticoagulant therapies were administered immediately, and a favorable clinical outcome was achieved.

Conclusion

This case highlights the fundamental role that echocardiography played in a patient in the intensive care unit who presented with shock secondary to pulmonary embolism with an unfavorable hemodynamic situation and in whom an unnecessary transfer to perform other complementary diagnostic tests was avoided. The combined use of electrocardiography and echocardiography provided a complete differential diagnosis, identifying the cause of shock and allowing the initiation of specific treatment without further delay. Knowledge of the echocardiographic results that are characteristic of pulmonary embolism can aid in the diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s13256-019-1994-y) contains supplementary material, which is available to authorized users.

Screening for Pulmonary Embolism with a D-Dimer Assay: Do we Still Need to Assess Clinical Probability as Well?

Clinical risk stratification and D-dimer assay can be of use in excluding pulmonary embolism in patients presenting to emergency departments but many D-dimer assays exist and their accuracy varies. We used clinical risk stratification combined with a quantitative latex-agglutination D-dimer assay to screen patients before arranging further imaging if required. Retrospective analysis of a sequential series of 376 patients revealed that no patient with a D-dimer of <275 ng/mL was diagnosed with pulmonary embolism, irrespective of clinical probability. We conclude that a latex-agglutination assay could be used to exclude pulmonary embolism without the necessity for clinical risk stratification. If these findings are borne out by further work, D-dimer strategies to exclude pulmonary embolism could substantially reduce imaging workload.

D-dimer and D-dimer/fibrinogen ratio in predicting pulmonary embolism in patients evaluated in a hospital emergency department

OBJECTIVES

The D-dimer level, fibrinogen level, and D-dimer/fibrinogen ratio are used in the diagnosis of pulmonary embolism, but results vary. We evaluated these parameters in the diagnosis of pulmonary embolism in emergency clinic patients.

METHODS

In this prospective study, 200 patients (pulmonary embolism, 100 patients; no pulmonary embolism, 100 patients) had D-dimer and fibrinogen levels measured before intervention. Pulmonary embolism was diagnosed with computed tomography angiography or ventilation-perfusion scintigraphy.

RESULTS

Compared with patients who did not have pulmonary embolism, patients who had pulmonary embolism had significantly greater mean D-dimer level (pulmonary embolism, 6±7 μg/ml; no pulmonary embolism, 1±1 μg/ml; P⩽0·001) and D-dimer/fibrinogen ratio (pulmonary embolism, 3±3; no pulmonary embolism, 0·4±0·4; P⩽0·001), but similar mean fibrinogen levels (pulmonary embolism, 337±184 mg/dl; no pulmonary embolism, 384±200 mg/dl; not significant). In patients who had pulmonary embolism, mean D-dimer level and D-dimer/fibrinogen ratio were greater in high-risk than non-high-risk patients. With D-dimer cutoff 0·35 μg/ml, sensitivity was high (100%) and specificity was low (27%) for pulmonary embolism. With D-dimer/fibrinogen ratio cutoff 0·13, sensitivity was high (100%) and specificity was low (37%) for pulmonary embolism.

CONCLUSION

A D-dimer level <0·35 μg/ml may exclude the diagnosis of pulmonary embolism. At a D-dimer cutoff 0·5 μg/ml and D-dimer/fibrinogen ratio cutoff 1·0, the D-dimer/fibrinogen ratio may have better specificity than D-dimer level in the diagnosis of pulmonary embolism, but the D-dimer/fibrinogen ratio may lack sufficient specificity in screening.

Pulmonary embolism

Pulmonary embolism (PE) remains one of the most challenging medical diseases in the emergency department. PE is a potentially life threatening diagnosis that is seen in patients with chest pain and/or dyspnea but can span the clinical spectrum of medical presentations. In addition, it does not have any particular clinical feature, laboratory test, or diagnostic modality that can independently and confidently exclude its possibility. This article offers a review of PE in the emergency department. It emphasizes the appropriate determination of pretest probability, the approach to diagnosis and management, and special considerations related to pregnancy and radiation exposure.

Utilization and yield of chest computed tomographic angiography associated with low positive D-dimer levels

BACKGROUND

It is unclear to what degree broadly applied D-dimer testing combined with a low threshold for imaging with even minimally positive results may be contributing to the utilization of chest computed tomographic angiography (CTA).

STUDY OBJECTIVES

To determine what proportion of chest CTAs for suspected pulmonary embolism (PE) were performed in the setting of minimally elevated D-dimer levels, and to determine the prevalence of PE in those patients when stratified by clinical risk.

METHODS

Retrospective chart review of all patients who had chest CTA for the evaluation of suspected PE during the years 2002-2006 in a suburban community teaching hospital emergency department.

RESULTS

There were 1136 eligible patient visits, of which 353 (31.1%) were found to have D-dimer levels in the low positive range (0.5-0.99 μg/mL). Of these 353 patients, 9 (2.6%; 95% confidence interval [CI] 0.9-4.2%) were diagnosed with PE. There were also 109 patients (9.6%) who had normal D-dimer levels (<0.5 μg/mL). Two of these 109 (1.8%; 95% CI 0-4.2%) were diagnosed with PE. When stratified by the Pulmonary Embolism Rule-out Criteria, 99 of 353 patients with low positive D-dimer levels (28.0%; 95% CI 23.4-32.7%), and 14 of 109 with normal D-dimer levels (12.8%; 95% CI 6.6-19.1%) were classified as low risk, none of whom had PE.

CONCLUSIONS

Nearly one-third of all chest CTAs were done for patients with minimally elevated D-dimer levels, and another 9.6% for patients with normal D-dimer levels with very low yield. Further research to define clinical criteria identifying patients with minimal risk of PE despite low positive D-dimer levels represents an opportunity to improve both patient safety and utilization efficiency of chest CTA.

A case of lower extremity venous thrombosis in the pediatric emergency department: associations with May-Thurner syndrome and isotretinoin use

Unilateral calf swelling and pain is not a common complaint in the pediatric emergency department. We present a case of a 17-year-old adolescent boy with no past medical history who presented with left leg swelling and pain while taking prednisone and isotretinoin. He was found to have an extensive occlusive thrombus throughout the deep venous system in his left leg. He was later diagnosed with May-Thurner syndrome, an anatomic variant in which the right iliac artery compresses the left iliac vein. We review the differential diagnosis, diagnostic workup, and initial ED management of deep venous thrombosis and provide a brief discussion of May-Thurner syndrome and the association of isotretinoin and vascular thrombi.

Update on techniques for the diagnosis of pulmonary embolism

IMPORTANCE OF THE FIELD

The clinical suspicion of acute pulmonary embolism (PE) is frequently raised. However, the diagnosis of PE is confirmed in only 20 - 30% of these patients. The high incidence in addition to the potential harm from false-positive or false-negative diagnostic decisions underline the importance of a standardised diagnostic algorithm with high sensitivity as well as specificity.

AREAS COVERED IN THIS REVIEW

This article reviews the diagnostic tests for the diagnosis of PE.

WHAT THE READER WILL GAIN

This review provides an overview of the different clinical decision rules (CDRs), D-dimer tests and imaging techniques in patients suspected of PE. Furthermore, the diagnostic process in patients with clinically suspected recurrent PE, suspicion during pregnancy and new research areas are discussed.

TAKE HOME MESSAGE

Various diagnostic tests are available to detect or exclude PE with good accuracy. CDRs and D-dimer tests play an important role in the exclusion of PE. Neither is sufficient as a single test, but the combination of an 'unlikely' clinical prediction and a normal D-dimer test result safely excludes PE. In case of a high CDR score and/or an elevated D-dimer concentration, extra imaging is necessary with multi-slice computed tomography pulmonary angiography as first choice modality.

Future developments in chest pain diagnosis and management

Much of the focus of research on patients with chest pain is directed at technological advances in the diagnosis and management of acute coronary syndrome (ACS), pulmonary embolism (PE), and acute aortic dissection (AAD), despite there being no significant difference at 4 years as regards mortality, ongoing chest pain, and quality of life between patients presenting to the emergency department with noncardiac chest pain and those with cardiac chest pain. This article examines future developments in the diagnosis and management of patients with suspected ACS, PE, AAD, gastrointestinal disease, and musculoskeletal chest pain.

Clinical conditions and patient factors significantly influence diagnostic utility of D-dimer in venous thromboembolism

Determining D-dimer levels remains important in the diagnostic algorithms for venous thromboembolism (VTE). The present study aimed to identify factors influencing D-dimer utility in diagnosing VTE. Consecutive symptomatic medical patients, who attended our emergency department from 1 November 2006 to 31 December 2006, had D-dimer levels measured as fibrinogen equivalent units (FEU), following clinical risk assessment. Diagnosis of VTE was established by venous compression ultrasonography and computed tomographic pulmonary angiography. VTE-negative patients were followed for 2 months to detect future occurrence of thromboembolism. Impact of various factors on D-dimer levels was analyzed. Four thousand and twenty-six patients attended our emergency department, and 525 patients (median age 52 years) had D-dimer assessed. Final diagnosis of VTE was established in 25 (4.7%) patients on radiological investigations. Median D-dimer levels for VTE-negative patients less than 60 years old, with normal renal function and chest radiology were 0.38 microgFEU/ml (range 0.19-2.3), 0.39 microgFEU/ml (range 0.17-3.5) and 0.39 microgFEU/ml (range 0.1-4.3), respectively. Similar figures for those at least 60 years, with renal impairment and abnormal chest radiology, were 0.75 microgFEU/ml (range 0.22-4.3), 0.52 microgFEU/ml (range 0.17-4.4) and 0.92 microgFEU/ml (range 0.26-5.6), respectively. Factors including patient age, renal function and chest radiology had significant influence on D-dimer levels (P < 0.01). A triad of patient age at least 60 years, renal impairment (modification of diet in renal disease stage 2-5) and abnormal chest radiology had a false positive D-dimer in 96% of patients (n = 72). Use of D-dimer in patients with a triad of advanced age, renal impairment and abnormal chest radiology has no practical diagnostic value in VTE.

Potential impact of adjusting the threshold of the quantitative D-dimer based on pretest probability of acute pulmonary embolism

OBJECTIVES

The utility of D-dimer testing for suspected pulmonary embolism (PE) can be limited by test specificity. The authors tested if the threshold of the quantitative D-dimer can be varied according to pretest probability (PTP) of PE to increase specificity while maintaining a negative predictive value (NPV) of >99%.

METHODS

This was a prospective, observational multicenter study of emergency department (ED) patients in the United States. Eligible patients had a diagnostic study ordered to evaluate possible PE. PTP was determined by the clinician's unstructured estimate and the Wells score. Five different D-dimer assays were used. D-dimer test performance was measured using 1) standard thresholds and 2) variable threshold values: twice (for low PTP patients), equal (intermediate PTP patients), or half (high PTP patients) of standard threshold. Venous thromboembolism (VTE) within 45 days required positive imaging plus decision to treat.

RESULTS

The authors enrolled 7,940 patients tested for PE, and clinicians ordered a quantitative D-dimer for 4,357 (55%) patients who had PTPs distributed as follows: low (74%), moderate (21%), or high (4%). At standard cutoffs, across all PTP strata, quantitative D-dimer testing had a test sensitivity of 94% (95% confidence interval [CI] = 91% to 97%), specificity of 58% (95% CI = 56% to 60%), and NPV of 99.5% (95% CI = 99.1% to 99.7%). If variable cutoffs had been used the overall sensitivity would have been 88% (95% CI = 83% to 92%), specificity 75% (95% CI = 74% to 76%), and NPV 99.1% (95% CI = 98.7% to 99.4%).

CONCLUSIONS

This large multicenter observational sample demonstrates that emergency medicine clinicians currently order a D-dimer in the majority of patients tested for PE, including a large proportion with intermediate PTP and high PTP. Varying the D-dimer's cutoff according to PTP can increase specificity with no measurable decrease in NPV.

Outcomes of high pretest probability patients undergoing d-dimer testing for pulmonary embolism: a pilot study

ELISA (enzyme-linked immunosorbent assay) D-dimer testing is commonly used in the evaluation of possible pulmonary embolism (PE) in the emergency department, but is not recommended in high pretest probability patients. Whether a negative ELISA D-dimer can safely rule out PE in these patients is not known, as there have been no large studies comparing ELISA D-dimer results and outcomes in high pretest probability patients. This was a prospective observational pilot study of emergency department patients evaluated for PE. Patients evaluated for PE had pretest probability assessed by the Wells PE Score. High pretest probability was defined as: dichotomized Wells Score>4 points and patients with trichotomized Wells Score>6 points. Patients had an ELISA D-dimer ordered by the treating physician. Pulmonary embolism was defined as: positive computed tomography scan, high probability ventilation/perfusion scan, positive pulmonary angiogram, or PE on 3-month follow-up. We calculated sensitivity, specificity, positive and negative predictive value, and likelihood ratios for the ELISA D-dimer. We prospectively enrolled 541 patients who underwent D-dimer testing for PE, of whom 130 patients had Wells Score>4 and 33 patients had Wells Score>6 (not mutually exclusive). Of subjects with Wells Score>4, 23 (18%) were diagnosed with PE and 40 (31%) had a negative D-dimer. No patient with Wells Score>4 (sensitivity 100%, 95% confidence interval [CI] 82%-100%; specificity 37%, 95% CI 28%-47%) or Wells Score>6 (sensitivity 100%, 95% CI 63%-100%; specificity 56%, 95% CI 35%-76%) who had a negative D-dimer was diagnosed with PE. The likelihood ratio for a negative D-dimer was 0 for both the Wells>4, and Wells>6 groups, however, the upper limits of the confidence interval around the post-test probability for PE were 16% and 33%, respectively, for these high probability groups. In this pilot study, the rapid ELISA D-dimer had high sensitivity and negative predictive value even when applied to patients with high pretest probability for PE. However, with the post-test probability of PE still as high as 16-33% in the negative D-dimer groups, this precludes applying the results to patient care at present. Further testing is warranted to determine whether these findings can be safely incorporated into practice.

Radiologic diagnoses of patients who received imaging for venous thromboembolism despite negative D-dimer tests

OBJECTIVE

The literature supports a negative D-dimer (-DD) excluding venous thromboembolic disease (VTE) in low-risk patients. We determined the radiologic diagnoses in patients where imaging was ordered despite a -DD.

METHODS

This is a retrospective chart review of patients with a -DD (Tinaquant; Roche Diagnostics, Mannheim, Germany) and a radiologic study within 48 hours, sought to determine radiologic diagnosis (primary outcome), treatment of VTE, and consensus diagnosis of acute VTE.

RESULTS

Among 3462 DD tests, 1678 met the inclusion criteria. Of 1362 patients with DD values of 350 ng/mL or less, 166 (12.2%) had radiologic studies: 93.4% of the final radiologic diagnoses were negative for VTE, 3.6% were indeterminate, and 3.0% (1.0%-6.9%) were positive; 1.8% ultimately had a consensus diagnosis of acute VTE. In 316 patients with DD values between 351 and 500 ng/mL, 88 (27.8%) had radiologic studies: 95.5% were negative, 1.1% were indeterminate, and 3.4% (0.7%-9.6%) were positive.

CONCLUSIONS

Of patients who receive radiologic studies despite -DD tests, 3.0% have positive radiologic diagnoses for acute VTE; only 1.8% had acute VTE after the review of their hospital course.

Echocardiography for management of hypotension in the intensive care unit

Hypotension is a common problem in critically ill patients. Rapid diagnosis and intervention may prevent this deterioration and improve eventual outcome. Echocardiography may make a critical difference in the rapid diagnosis of both common and uncommon but important causes of hypotension, such as pericardial tamponade. The differential diagnosis for hypotension differs between acutely admitted septic or trauma patients and the chronic patient in the intensive care unit. A better approach to patient evaluation is the performance of a comprehensive evaluation on every patient. A comprehensive examination is less likely to miss an unexpected diagnosis. With practice, a complete examination may be performed in minutes. Preload, contractility, systolic function (global and focal), and assessment of diastolic dysfunction (common cause of congestive heart failure) can be performed quickly. Specific situations like pericardial tamponade, pulmonary embolism, left ventricular outflow tract obstruction, unexplained hypoxemia, and aortic dissection, among others, can all be reliably performed using transesophageal echocardiography. Appropriate training and utilization of this technology will essentially help better manage hypotension in critically ill patients and thereby may improve their outcome. An algorithm to this effect has been suggested, although the same results can be achieved with different algorithms or approaches.

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.

Prognostic Value of Arterial/Alveolar Oxygen Tension Ratio (a/APO2) in Acute Pulmonary Embolism

BACKGROUND

Because the arterial/alveolar oxygen tension ratio (a/APO2) is relatively constant throughout the entire range of fractional inspired oxygen concentration (FiO2), its use in determining the prognosis of acute pulmonary embolism (APE) was investigated.

METHODS AND RESULTS

This study retrospectively assessed 202 consecutive patients with APE confirmed by computed tomography or high probability lung scintigraphy. All patients underwent initial arterial blood gas analysis during the first 24 h of admission. Receiver-operating characteristic analyses were performed to determine the a/APO2 cut-off value for predicting 30-day death or 30-day composite events. Cut-off values for a/APO2 were used to determine stability in all patients and 2 subgroups (0.49 for all patients; 0.49 for FiO2 =0.21; 0.46 for FiO2 >0.21). Using the cut-off value of a/APO2 <0.49 for predicting 30-day death, the negative predictive value (NPV) was 90%, and the positive predictive value (PPV) was 30.3%. For the 30-day composite end point, the NPV was 81.3%, and the PPV was 40.9%. Excluding massive APE, the a/APO2 also had high NPV and moderate PPV in predicting short-term prognosis. This study additionally demonstrated a linear relationship between platelet count and a/APO2.

CONCLUSIONS

The cut-off value of a/APO2 <0.49 exhibits stability at variable FiO2 values and is a useful prognostic predictor in APE.

A highly sensitive ELISA D-dimer increases testing but not diagnosis of pulmonary embolism

OBJECTIVES

To determine the effect of introducing a rapid enzyme-linked immunosorbent assay (ELISA) D-dimer on the percentage of emergency department (ED) patients evaluated for pulmonary embolism (PE), the use of associated laboratory testing, pulmonary vascular imaging, and the diagnoses of PE.

METHODS

Patients evaluated for PE during three 120-day periods were enrolled: immediately before (period 1), immediately after (period 2), and one year after the introduction of a rapid ELISA D-dimer in the hospital. The frequency of ED patients evaluated for PE with any test, with D-dimer testing, and with pulmonary vascular imaging and the frequency of PE diagnosis during each time period were determined.

RESULTS

The percentage of patients evaluated for PE nearly doubled; from 1.36% (328/24,101) in period 1 to 2.58% (654/25,318) in period 2 and 2.42% (583/24,093) in period 3. The percentage of patients who underwent D-dimer testing increased more than fourfold; from 0.39% (93/24,101) in period 1 to 1.83% (464/25,318) in period 2 and 1.77% (427/24,093) in period 3. The percentage of patients who underwent pulmonary vascular imaging increased from 1.02% (247/24,101) in period 1 to 1.36% (344/25,318) in period 2 and to 1.39% (334/24,093) in period 3. There was no difference in the percentage of patients diagnosed as having PE in period 1 (0.20% [47/24,101]), period 2 (0.27% [69/25,318]), and period 3 (0.24% [58/24,093]).

CONCLUSIONS

In the study's academic ED, introduction of ELISA D-dimer testing was accompanied by an increase in PE evaluations, D-dimer testing, and pulmonary vascular imaging; there was no observed change in the rate of PE diagnosis.

Acute Pulmonary Embolism: Imaging in the Emergency Department

Acute pulmonary embolism (PE) is a life-threatening condition that requires accurate diagnostic imaging. Morbidity and mortality that result from PE can be reduced significantly if appropriate treatment is initiated early; this makes timely diagnosis imperative. Historically, the gold standard for the imaging of PE has been pulmonary angiography. Rapid advances in radiology and nuclear medicine have led to this modality largely being replaced by noninvasive techniques, most frequently multidetector helical CT pulmonary angiography (CTPA). In cases in which CTPA is contraindicated, other modalities for diagnosis of PE include nuclear ventilation perfusion scanning, magnetic resonance pulmonary angiography, duplex Doppler ultrasonography for deep venous thrombosis, and echocardiography. This article reviews the literature on the role of these imaging modalities in the diagnosis of PE.

Diagnostic and therapeutic strategy for acute pulmonary thromboembolism

BACKGROUND

The diagnostic and therapeutic strategy for acute pulmonary thromboembolism (APTE) was published by the Japanese Circulation Society. But in Japan, there has been no report on how to improve the pre-test probability in APTE-suspected cases, to determine a practically available diagnostic strategy, nor has been a report that compares diagnostic methods and therapies for APTE by decision analysis.

METHODS AND RESULTS

APTE was found in 66.7% before using diagnostic imaging techniques. Compared with the absence of APTE, prolonged immobilization, cancer, tachycardia, unilateral leg swelling and inverted T-wave in V(1-3) were found more often in the presence of APTE. The rate of obtaining the result on the day of ordering the examination test was 100% with arterial blood gas analysis, trans-thoracic echocardiography and computed tomography (CT), 78.2% in D-dimer, 85.5% in pulmonary angiography, and 54.5% in perfusion lung scan. Decision analysis showed that the highest expected utility was anticoagulant over 0.51 in pre-test probability, with CT between 0.13 and 0.51.

CONCLUSIONS

The pre-test probability of APTE has already been high before using specific diagnostic imaging techniques in Japan. Our results showed that the diagnostic strategy for APTE made by the Japanese Circulation Society was available in most hospitals in Japan.

D-dimer testing: advantages and limitations in emergency medicine for managing acute venous thromboembolism

D-dimer values can be rapidly determined and used for the management of acute venous thromboembolism (VTE). However, its role in the setting of emergency still remains unclear and inappropriate testing is a significant clinical problem. This review discusses the currently used assays, clinical indications, and limitations of D-dimer measurement. Studies in English language were identified by searching PubMed from December 1985 to December 2005. Available literature on D-dimer was identified from Medline, along with cross referencing from the reference lists of major articles and reviews on this subject. Among 56 articles collected, 14 papers, 4 overviews and 1 systemic review were selected accordingly to predefined criteria. Data synthesis shows that D-dimer testing has sufficient diagnostic accuracy for ruling out acute VTE if used in combination with standardised clinical judgement. D-dimer seems to be also a useful tool for managing suspected VTE patients in absence of immediate imaging. Attention should be paid to exclude conditions that may affect the accuracy of the test, such as concomitant disease, heparin administration and symptom duration >15 days. Although enzyme-linked immunosorbent assay determination has the highest accuracy, immunoturbidimetric assay seems the most suitable on an emergency basis because of its rapid performance. In conclusion, at present D-dimer testing can be safely used in the management of acute VTE in emergency medicine. However, because of its heterogeneity related to the method used and setting implemented, it is preferable to assess D-dimer accuracy before its implementation in management strategies for VTE.

The effect of single-detector CT versus MDCT on clinical outcomes in patients with suspected acute pulmonary embolism and negative results on CT pulmonary angiography

OBJECTIVE

We sought to compare the clinical outcomes of patients in whom pulmonary embolism (PE) has been ruled out with single-detector CT versus MDCT, given the improved visualization of subsegmental clots with the latter and the recent increase in use of CT for evaluation of PE.

SUBJECTS AND METHODS

Two cohorts of patients undergoing CT for suspected PE with either single-detector CT (3-mm collimation and pitch of 1.7) or MDCT (2-mm collimation and pitch of 1) scanners were prospectively observed and compared using predefined criteria for evidence of subsequent thromboembolic disease during the 6 months after the acquisition of their initial scan.

RESULTS

Ninety-eight patients were scanned using a single-detector CT scanner. Of these, none had evidence of subsequent PE or deep venous thrombosis (DVT), and six (6.1%) died of unrelated causes. Of the 100 patients scanned using an MDCT scanner, one (1.0%) had a subsequent nonfatal PE 2 months after the initial scanning, one (1.0%) had DVT 1 month after the initial scanning, and eight (8.0%) died of unrelated causes. No significant difference was found in either the probability of subsequent thromboembolic events (chi(2) = 0.3183, degrees of freedom [df] = 1, p = 1) or frequency of unrelated deaths (chi(2) = 0.2655, df = 1, p = 0.7829) between patients scanned using single-detector CT or MDCT protocols.

CONCLUSION

Our results show that patients with suspected acute PE and negative CT results have acceptable clinical outcomes in the absence of anticoagulation treatment up to 6 months after acquisition of their initial scan. Furthermore, we found that the increased visualization of smaller, more peripheral arteries afforded by multislice technology did not affect clinical outcome.

Screening for pulmonary embolism with a D-dimer assay: do we still need to assess clinical probability as well?

Clinical risk stratification and D-dimer assay can be of use in excluding pulmonary embolism in patients presenting to emergency departments but many D-dimer assays exist and their accuracy varies. We used clinical risk stratification combined with a quantitative latex-agglutination D-dimer assay to screen patients before arranging further imaging if required. Retrospective analysis of a sequential series of 376 patients revealed that no patient with a D-dimer of <275 ng/mL was diagnosed with pulmonary embolism, irrespective of clinical probability. We conclude that a latex-agglutination assay could be used to exclude pulmonary embolism without the necessity for clinical risk stratification. If these findings are borne out by further work, D-dimer strategies to exclude pulmonary embolism could substantially reduce imaging workload.

CT pulmonary angiography: a comparative analysis of the utilization patterns in emergency department and hospitalized patients between 1998 and 2003

OBJECTIVE

The purpose of our study was to objectively examine the temporal utilization patterns of CT pulmonary angiography in emergency department and hospitalized patients in an academic tertiary care center.

SUBJECTS AND METHODS

Patients who underwent CT examination for suspected pulmonary embolism either through our emergency department or as inpatients during a recent 9-month interval were identified. The absolute number of studies and incidence of positive results and ancillary findings were compared with similar data published from our institution during the corresponding 9-month interval in 1997-1998.

RESULTS

The overall number of patients imaged for pulmonary embolism was significantly greater in the 2002-2003 period than in the 1997-1998 period (homogeneity of rates = 88.45, p < 0.0001). The absolute number of scans obtained was significantly greater in both the emergency department (chi(2) = 167.03, p < 0.0001) and inpatient (chi(2) = 210.62, p < 0.0001) groups in the more recent population. Significantly fewer ancillary findings were reported in both the emergency department (chi(2) = 5.93, p = 0.019) and inpatient (chi(2) = 6.03, p = 0.015) groups in the more recent population. The incidence of CT-detected pulmonary embolism was significantly less in both the emergency department (chi(2) = 34.26, p < 0.0001) and inpatient (chi(2) = 8.52, p < 0.01) groups in the more recent population. This decrease in the incidence of scans with positive findings for pulmonary embolism over time was significantly greater in the emergency department group than the inpatient group (homogeneity of odds = 0.003, p < 0.007).

CONCLUSION

The evolution of CT pulmonary angiography utilization has led to a significant increase in the number of patients being imaged for pulmonary embolism with a coincident significant decrease in the rates of CT-detected pulmonary embolism and ancillary findings both in emergency department and hospitalized patients.

Impact of a rapid rule-out protocol for pulmonary embolism on the rate of screening, missed cases, and pulmonary vascular imaging in an urban US emergency department

STUDY OBJECTIVE

This study tests the hypothesis that implementation of a point-of-care emergency department (ED) protocol to rule out pulmonary embolism would increase the rate of evaluation without increasing the rate of pulmonary vascular imaging or ED length of stay and that less than 1.0% of patients with a negative protocol would have an adverse outcome.

METHODS

A baseline study was conducted on patients with suspected pulmonary embolism at an urban ED to establish baseline measurements performed when only pulmonary vascular imaging was available to rule out pulmonary embolism. The intervention protocol used pretest probability assessment, a whole-blood d -dimer assay, and an alveolar dead-space measurement to rule out pulmonary embolism. The main outcomes were diagnosis of venous thromboembolism or sudden unexpected death within 90 days.

RESULTS

During baseline, 453 of 61,322 patients (0.74%; 95% confidence interval [CI] 0.67% to 0.81%) underwent pulmonary vascular imaging, and 8% (95% CI 6% to 11%) of scan results were positive; 1.20% (95% CI 0.39% to 2.78%) of untreated discharged patients were anticoagulated for venous thromboembolism or died unexpectedly within 90 days. The median length of stay was 385 minutes. After intervention, 1,460 of 102,848 patients (1.42%; 95% CI 1.35% to 1.49%) were evaluated for pulmonary embolism. Seven hundred fifty-two patients had a negative protocol and 5 of 752 (0.66%; 95% CI 0.20% to 1.54%) had venous thromboembolism within 90 days, none with unexpected death. After intervention, the rate of pulmonary vascular imaging tended to decrease (0.64%; 95% CI 0.59% to 0.69%), and more scans (11%; 95% CI 9% to 14%) were read as positive; the length of stay decreased to 297 minutes.

CONCLUSION

A point-of-care pulmonary embolism rule-out protocol doubled the rate of screening for pulmonary embolism in the ED, had a false negative rate of less than 1.0%, did not increase the pulmonary vascular imaging rate, and decreased length of stay.

Prospective validation of wells criteria in the evaluation of patients with suspected pulmonary embolism

STUDY OBJECTIVE

The literature suggests that the d -dimer is useful in patients suspected of having pulmonary embolism and who have a low pretest probability of disease. A previously defined clinical decision rule, the Wells Criteria, may provide a reliable and reproducible means of determining this pretest probability. We evaluate the interrater agreement and external validity of Wells Criteria in determining pretest probability in patients suspected of having pulmonary embolism.

METHODS

This was a prospective observational study. Trained research assistants enrolled patients during 120 random 8-hour shifts. Patients who underwent imaging for pulmonary embolism after a medical history, physical examination, and chest radiograph were enrolled. Treating providers and research assistants determined pretest probability according to Wells Criteria in a blinded fashion. Two d -dimer assays were run. Three-month follow-up for the diagnosis of pulmonary embolism was performed. Interrater agreement tables were created. kappa Values, sensitivities, and specificities were determined.

RESULTS

Of the 153 eligible patients, 3 patients were missed, 16 patients declined, and 134 (88%) patients were enrolled. Sixteen (12%) patients were diagnosed with pulmonary embolism. The kappa values for Wells Criteria were 0.54 and 0.72 for the trichotomized and dichotomized scorings, respectively. When Wells Criteria were trichotomized into low pretest probability (n=59, 44%), moderate pretest probability (n=61, 46%), or high pretest probability (n=14, 10%), the pulmonary embolism prevalence was 2%, 15%, and 43%, respectively. When Wells Criteria were dichotomized into pulmonary embolism-unlikely (n=88, 66%) or pulmonary embolism-likely (n=46, 34%), the prevalence was 3% and 28%, respectively. The immunoturbidimetric and rapid enzyme-linked immunosorbent assay d -dimer assays had similar sensitivities (94%) and specificities (45% versus 46%).

CONCLUSION

Wells Criteria have a moderate to substantial interrater agreement and reliably risk stratify pretest probability in patients with suspected pulmonary embolism.

Diagnosis of pulmonary embolism: a cost-effectiveness analysis

OBJECTIVE

Pulmonary embolism is a major cause of maternal death. The work up for suspected pulmonary embolism is complex, with many potential diagnostic options. We performed a cost analysis to evaluate which of several diagnostic strategies was the most cost-effective with the least number of deaths from pulmonary embolism.

STUDY DESIGN

We created a decision tree to evaluate the following strategies: (1) Compression ultrasonography followed by anticoagulation (if there is a positive result) or secondary tests, ventilation perfusion scans or spiral computed tomography (if there is a negative result); high probability ventilation perfusion scans (a positive test result) resulted in anticoagulation; low probability ventilation perfusion scans (a negative test) resulted in no treatment; intermediate tests that resulted in a second test (computed tomography or pulmonary angiography). (2) Ventilation perfusion scans as a primary test followed by anticoagulation. (3) Computed tomography followed by anticoagulation (if there is a positive result). The following assumptions were made: The incidence of pulmonary embolism in pregnant women with suspected pulmonary embolism is 5%; 40% of documented pulmonary embolisms have a positive compression ultrasound result; 10% of ventilation perfusion scans for suspected pulmonary embolism are high probability, 60% are indeterminate, and 30% are low probability for pulmonary embolism; the sensitivity of computed tomography is 95%; the sensitivity of angiography is 98%. The assumed mortality rate of treated pulmonary embolism is 0.7% and of untreated pulmonary embolism in pregnancy is 15% (range, 10%-50%). The angiography-associated mortality rate is 0.5%, and the anticoagulation associated mortality rate is 0.2%. The following costs were used for the model: compression ultrasonography, 200.00 dollars; ventilation perfusion scans, 400.00 dollars; angiography, 1000.00 dollars; computed tomography, 500.00 dollars; and anticoagulation, 5982.00 dollars. With baseline assumptions, spiral computed tomography as the initial diagnostic regimen was found to be the most cost-effective at 17,208 dollars per life saved. Sensitivity analyses were performed over a wide range of assumptions that included alteration of the probability of pulmonary embolism, the sensitivity of computed tomography, ventilation perfusion scans, and compression ultrasonography, the cost of computed tomography, and the mortality rate of untreated pulmonary embolism. Our findings remained robust over a wide range of assumptions.

CONCLUSION

Suspected pulmonary embolism remains a diagnostic quandary. Our analysis indicated that spiral computed tomography offers the most cost-effective method for diagnosing this potentially fatal condition.

Cardiac ultrasound

The use of echocardiography in the ED is well established and continues to gain widespread use in the evaluation of critically ill patients. In certain circumstances such as chest trauma, pericardial effusion, and cardiac arrest,EPs can perform and interpret echocardiographic examinations reliably. In other circumstances such as the diagnosis of acute coronary syndromes, PE,and endocarditis, the EP should be aware of the uses and limitations of echocardiography and obtain appropriate consultation when necessary.Academic- and community-based EPs should seek to incorporate further the use of echocardiography in their respective clinical practices, with special attention given to training and quality assurance. As EPs continue to improve their skills in cardiac ultrasound, their ability to diagnose a wider spectrum of cardiac diseases undoubtedly will grow proportionally.

A rapid quantitative turbimetric d-dimer assay has high sensitivity for detection of pulmonary embolism in the ED

Many rapid d-dimer assays are commercially available with wide ranges of reported sensitivities, often based on small sample sizes. This has limited their intended use as rapid and inexpensive tests to evaluate pulmonary embolism in the low-risk patient. We sought to determine the sensitivity of the STA-Liatest D-Di d-dimer assay in our ED. We performed a retrospective analysis of 103 patients seen in our ED with the admitting diagnosis of known or suspected pulmonary embolism. These charts were assessed to establish if a d-dimer assay was performed within 24 hours. These charts were then reviewed to determine what diagnostic studies were performed and what final diagnosis was reached. Of the 103 charts identified, 55 had d-dimer assays performed within 24 hours. Of those, 38 were diagnosed with pulmonary embolism; none had negative d-dimer assays (<400 ng/mL). Using the exact method, the sensitivity of this assay was calculated to be 100% with a 95% confidence interval (CI) of 91.4% to 100%. Our results suggest that the STA-Liatest D-Di d-dimer assay could have an adequate sensitivity to be used to rule out pulmonary embolism in low-risk patients. Further prospective studies with larger sample sizes are required to validate this observation.

Inferior Vena Cava Filter is a New Additional Therapeutic Option to Reduce Mortality From Acute Pulmonary Embolism

BACKGROUND

There are few reports that examine the current imaging and management techniques according to the severity of acute pulmonary embolism (APE) or that clarify whether the management strategy ameliorated the mortality from APE.

METHODS AND RESULTS

The study group were 456 patients with APE who were clinically diagnosed before their death. The severity at diagnosis, and the imaging and management techniques were analyzed. Mortality from APE was 0.8% in patients without shock nor right ventricular overload, 2.7% in patients with right ventricular overload without shock, 15.6% in patients with shock, and 52.4% in patients with cardiopulmonary arrest (p<0.0001). In the more severe cases, pulmonary angiography and trans-thoracic echocardiography were used more frequently, whereas both ventilation and perfusion lung scans were used less frequently. Computed tomography was used widely, regardless of the severity. Thrombolytic therapy and catheter therapy were used more frequently in the more severe cases, but an inferior vena cava filter was the only management strategy that reduced the mortality from APE.

CONCLUSIONS

The severity of APE at diagnosis affected the selection of both the diagnostic techniques and the type of management. Implantation of inferior vena cava filters reduced the mortality from APE.

Turbidimetric D-Dimer Test in the Diagnosis of Pulmonary Embolism: A Metaanalysis

Background: Clinicians in outpatient clinics and emergency departments desire an accurate quantitative D-dimer assay. The study objective was to evaluate the diagnostic performance characteristics of the latex turbidimetric D-dimer test in the diagnosis of pulmonary embolism (PE) in the emergency department population.

Methods: We conducted a search of MEDLINE, EMBASE, and bibliographies of previous systematic reviews with no language restriction. Experts in the field of PE research were contacted to identify unpublished studies. Prospective investigations involving predominately outpatient populations with suspected PE that used a turbidimetric D-dimer test were included. Two authors extracted data independently and assessed study quality based on the composition of the patient spectrum and the reference standard used. Consensus was reached by conference. The analysis was based on a summary ROC curve and combining sensitivity and specificity independently across studies using a random-effects model.

Results: The search yielded 264 publications and 2 unpublished studies. Nine studies met the inclusion criteria and provided a sample of 1901 individuals. Eight of the nine studies were homogeneous in terms of both sensitivity and specificity. One study had similar sensitivity but higher specificity. Combining the studies yielded an overall sensitivity of 0.93 (95% confidence interval, 0.89–0.96) and an overall specificity of 0.51 (95% confidence interval, 0.42–0.59).

Conclusions: The turbidimetric D-dimer test is sensitive but nonspecific for the detection of PE in the emergency department setting. D-Dimer tests using latex turbidimetric methods appear to have test characteristics comparable to those for ELISA methods.

Methodology for a rapid protocol to rule out pulmonary embolism in the emergency department

We propose an emergency department (ED) pulmonary embolism rule-out protocol based on pretest probability assessment coupled with either a negative D -dimer assay result or a negative D -dimer assay result plus a normal alveolar dead-space measurement. We examine the safety, efficiency, and feasibility of such a protocol, paying special attention to implicit and explicit strategies of pretest probability assessment among patients with suspected pulmonary embolism. Finally, we assess the potential effect of the proposed pulmonary embolism rule-out protocol on use of imaging resources and ED throughput.

ELISA D-dimer measurement for the clinical suspicion of pulmonary embolism in the emergency department: one-year observational study of the safety profile and physician's prescription

OBJECTIVES

To validate the safety profile of a rapid ELISA D-dimer as the first diagnostic step in the clinical suspicion of pulmonary embolism (PE) in outpatients admitted to an emergency department (ED), and to retrospectively evaluate the appropriateness of the physician's prescription.

DESIGN AND SETTING

An observational study of all patients admitted to the ED of an urban university teaching hospital with signs and symptoms justifying the prescription of a rapid ELISA D-dimer measurement (Vidas; Biomerieux; France) as the first line diagnostic test for PE. Acute PE was established or excluded according to an appropriate combination of the D-dimer concentration, the lung scintigraphy, the spiral computerized tomography (spiral CT), the venous ultrasonography, and the arteriography in case of uncertain results. All patients with D-dimer values under the cut-off point of 500 ng/ml were followed up after 6 months.

RESULTS

395 patients were studied. A normal D-dimer concentration < 500 ng/ml was found in 179 patients (45% of the cohort). The retrospective analysis showed that none of these patients were found to have a high pre-test clinical probability. None of these 179 patients received anticoagulation nor displayed a PE event during a 6-month period (negative predictive value 100%; 95% CI, 98.0 to 100%; sensitivity 100%; 95% CI, 90.3 to 100%). Among the 216 patients (55%) with D-dimer values above 500 ng/ml, PE was confirmed in 32 cases, for a prevalence of the disease of 8.1%. Eighty-six patients (22%) had no additional testing in spite of positive D dimer values > 500 ng/ml, pointing out a 22% rate of inappropriate use of the D-dimer measurement.

CONCLUSION

This observational study confirms that a normal rapid ELISA D-dimer value (< 500 ng/ml) used as a first diagnostic step in ruling out the diagnosis of PE is a safe clinical practice when the pre-test clinical probability is low or intermediate. Nevertheless, the low prevalence rate of the disease (8.1%) suggests a potential overused and inappropriate prescription.

Diagnosing pulmonary embolism: a question of too much choice?

The diagnosis of pulmonary embolism (PE) is difficult with many patients treated without the disease or left untreated without an adequate diagnostic work up. Recent advances in PE diagnosis are reviewed. The use of risk stratification in PE diagnosis is strongly recommended and evidence on how it can best be performed summarized. The Ginsberg/Wells stratification rule is recommended currently as the best validated rule. Computed tomographic pulmonary angiography (CTPA) was found to have quite poor sensitivity and to be poorly validated. It is recommended as adequate as a positive test in moderate/high risk groups and an exclusionary test in low risk groups or where an adequate alternative diagnosis is found. For D-Dimer tests the only test with adequate sensitivity and validation in management studies is the VIDASCopyright D-Dimer. This is in low/intermediate risk groups in the ED population. The Simpli-RedCopyright test is also reviewed but is too insensitive for most populations. Echocardiography: this is good in compromised patients as it is a bedside test which when negative virtually excludes PE. If positive in the right setting it has a high positive predictive value. A negative echocardiogram predicts a benign clinical course for PE. The rest of the paper details the authors approach to integrating these new techniques with established algorithms and where progress is likely to occur in the next few years. These include improvements in CTPA (plus the addition of CT venography), new point of care D-Dimer tests, better risk stratification rules and integration of new strategies with artificial neural networks or computerized guidelines.

Pulmonary embolism

PE is one of the great challenges in medicine. It is a disease that carries with it a high mortality rate, yet no historical piece of information, physical examination finding, or diagnostic modality is perfect at excluding its possibility. Emergency physicians must be vigilant about considering PE in the differential diagnosis of a variety of presenting complaints and must use a variety of diagnostic and therapeutic options as they manage patients with suspected or confirmed PE. The diagnostic options range from bedside diagnostic tests to highly specialized imaging available at only specialized institutions. Knowing the advantages and disadvantages of each of the diagnostic modalities assists the physician in employing the best test. Therapeutic options also vary widely and include anticoagulation, vena caval interruption, systemic thrombolysis, embolectomy, and other therapeutic adjuncts, such as ECMO and inhaled nitric oxide. Similarly, awareness of the indications and contraindications to the varied therapeutic agents ensures appropriate therapy when the diagnosis is made.

Clinical policy: critical issues in the evaluation and management of adult patients presenting with suspected pulmonary embolism

This clinical policy focuses on critical issues in the evaluation and management of patients with signs or symptoms of pulmonary embolism (PE). A MEDLINE search for clinical trials published from January 1995 through April 2001 was performed using the key words "pulmonary embolus" with limits of "clinical investigations" and "clinical policies." Subcommittee members and expert peer reviewers also supplied articles with direct bearing on the policy. This policy focuses on 2 major areas of current interest and/or controversy: (1) diagnostic: utility of D -dimer, ventilation-perfusion scanning, and spiral computed tomography angiogram in the evaluation of PE; and (2) therapeutic: indications for fibrinolytic therapy. Recommendations for patient management are provided for each 1 of these topics based on strength of evidence (Level A, B, or C). Level A recommendations represent patient management principles that reflect a high degree of clinical certainty; Level B recommendations represent patient management principles that reflect moderate clinical certainty; and Level C recommendations represent other patient management strategies based on preliminary, inconclusive, or conflicting evidence, or based on panel consensus. This guideline is intended for physicians working in emergency departments or chest pain evaluation units.

Can a state-of-the-art D-dimer test be used to determine the need for CT imaging in patients suspected of having pulmonary embolism?

RATIONALE AND OBJECTIVES

The purpose of this study was to determine whether a simple rapid blood test can obviate computed tomography (CT) in a sizable percentage of patients suspected of having pulmonary embolism, based on the hypothesis that negative D-dimer results could eliminate any further search for pulmonary embolism.

MATERIALS AND METHODS

At the authors' institution, 2,121 sequential patients underwent a whole-blood antibody agglutination test for cross-linked fibrin degradation products (D-dimer). Of these patients, 844 had positive test results and were not further considered. A retrospective review included reports of all multisection combined CT venographic and pulmonary angiographic studies obtained within 48 hours of the D-dimer assay for the 1,277 patients with negative D-dimer results; 229 (18%) of these 1,277 patients underwent combined CT venography and pulmonary angiography, usually within 24 hours.

RESULTS

Retrospective review of the imaging examinations that were discrepant with the D-dimer results revealed only three false-negative D-dimer results. Of the 229 patients in whom combined CT venography and pulmonary angiography was performed for suspected pulmonary embolism, 226 (98.7%) had no evidence of acute pulmonary embolism or deep venous thrombosis. The negative predictive value of a negative D-dimer result was therefore 98.7% (confidence interval, 96.2%-99.7%).

CONCLUSION

The D-dimer assay is a simple rapid blood test that is sensitive to the presence of acute thrombosis. Very few patients with negative results have acute deep venous thrombosis or pulmonary embolism, with combined CT venography and pulmonary angiography used as the reference standard.

The accuracy of the enzyme-linked immunosorbent assay D-dimer test in the diagnosis of pulmonary embolism: a meta-analysis

STUDY OBJECTIVE

We sought to determine the sensitivity and specificity of the enzyme-linked immunosorbent assay (ELISA) D -dimer test in the diagnosis of pulmonary embolism (PE) in the adult emergency department population.

METHODS

A search of MEDLINE, EMBASE, and bibliographies of previous systematic reviews was conducted, with no language restriction. Experts in the field of PE research were contacted to identify unpublished studies. Prospective investigations involving a predominately outpatient population suspected of PE that used ELISA D -dimer tests were included. Two authors extracted data independently and assessed study quality on the basis of the patient spectrum and reference standard. Consensus was reached by means of conference. The analysis was based on a summary receiver operating characteristic curve and pooled estimates for sensitivity and specificity by using a random-effects model.

RESULTS

The search yielded 52 publications. No unpublished studies were found. Eleven studies met the inclusion criteria and provided a sample of 2,126 patients. The summary receiver operating characteristic curve analysis found significant heterogeneity among the 11 studies. Subgroup analysis of the 9 studies that used traditional ELISA D -dimer methods yielded the most valid pooled estimates, with a sensitivity of 0.94 (95% confidence interval [CI] 0.88 to 0.97) and a specificity of 0.45 (95% CI 0.36 to 0.55). Advanced age resulted in a lower specificity. A prolonged duration of symptoms decreased the sensitivity and specificity.

CONCLUSION

The ELISA D -dimer test is highly sensitive but nonspecific for the detection of PE in the clinical setting. This test might help clinicians safely rule out PE, especially in the face of low and low-to-moderate pretest probabilities.

Criteria for the safe use of D-dimer testing in emergency department patients with suspected pulmonary embolism: a multicenter US study

STUDY OBJECTIVE

We derive a decision rule to partition emergency department patients with suspected pulmonary embolism (PE) into a small, high-risk group (>40% pretest probability) that is unsafe for D -dimer testing and a larger group that is safe to have PE ruled out with either a whole-blood D -dimer plus alveolar deadspace measurement or a quantitative D -dimer assay.

METHODS

Nine hundred thirty-four patients with suspected PE were studied at 7 urban EDs in the United States. Patients were prospectively interviewed and examined for recognized symptoms, signs, and risk factors associated with PE. These data were collected before standard objective imaging for PE. Selected variables were analyzed by multivariate logistic analysis to determine factors associated with PE (P <.05). A decision rule was then constructed to categorize approximately 80% of ED patients as safe for D -dimer testing.

RESULTS

Pretest prevalence of PE was 19.4% (181/934; 95% confidence interval [CI] 16.3% to 21.7%). Six variables found to be significant on multivariate analysis were used to construct the decision rule. Unsafe patients had either a shock index (heart rate/systolic blood pressure) more than 1.0 or age older than 50 years, together with any one of the following conditions: unexplained hypoxemia (SaO (2) <95%; no prior lung disease), unilateral leg swelling, recent major surgery, or hemoptysis. These criteria were met by 197 (21.0%) of 934 patients, and 83 of 197 (42.1%; 95% CI 35.3% to 49.6%) patients had PE. Exclusion of these 197 unsafe patients significantly decreased the probability of PE in the remaining 737 (79.0%) safe patients to 13.3% (95% CI 10.9% to 15.9%).

CONCLUSION

Simple clinical criteria can permit safe D -dimer testing in the majority of ED patients with suspected PE. These criteria warrant prospective validation.