Assessing clinical probability of pulmonary embolism in the emergency ward: a simple score

Diagnosing pulmonary embolism

Objective testing for pulmonary embolism is necessary, because clinical assessment alone is unreliable and the consequences of misdiagnosis are serious. No single test has ideal properties (100% sensitivity and specificity, no risk, low cost). Pulmonary angiography is regarded as the final arbiter but is ill suited for diagnosing a disease present in only a third of patients in whom it is suspected. Some tests are good for confirmation and some for exclusion of embolism; others are able to do both but are often non-diagnostic. For optimal efficiency, choice of the initial test should be guided by clinical assessment of the likelihood of embolism and by patient characteristics that may influence test accuracy. Standardised clinical estimates can be used to give a pre-test probability to assess, after appropriate objective testing, the post-test probability of embolism. Multidetector computed tomography can replace both scintigraphy and angiography for the exclusion and diagnosis of this disease and should now be considered the central imaging investigation in suspected pulmonary embolism.

External validation and comparison of recently described prediction rules for suspected pulmonary embolism

PURPOSE OF REVIEW

The assessment of pretest probability, allowing the categorization of patients clinically suspected of having pulmonary embolism in low, intermediate, and high clinical probability, is an essential step in contemporary diagnostic strategies because it permits limiting the number of additional diagnostic tests, especially invasive tests. Clinical probability can be evaluated implicitly or by prediction rules. Two prediction rules for pulmonary embolism have been described: the Canadian prediction rule (the Wells score) and the Geneva prediction rule. Their original descriptions were published in 2000 and 2001, respectively. These prediction rules need to be externally validated, and, ideally, outcome studies should demonstrate that patients may be safely treated on the basis of the assessment of the clinical probability they provide. Therefore, the purpose of this review is to discuss the external validation of these rules, because this particular point has been only recently achieved.

RECENT FINDINGS

Application of both rules in an external setting and in a prospective study have confirmed their validity. A recent study suggests that the best evaluation is probably based on a prediction rule associated with possible clinical override.

SUMMARY

Studies comparing an empiric assessment with explicit assessment, such as the Wells simplified score or the Geneva score, have shown that the three tools show similar accuracy. External validation and use of both rules in prospective management studies have only recently been performed and have confirmed their validity. Some reports suggest that empiric assessment may be influenced by level of training. Objective prediction rules seems to be less influenced by experience and should be preferred by more junior doctors. The tool used for clinical probability assessment is probably less important than the principle of a careful clinical probability assessment in each patient with suspected pulmonary embolism.

Étude BPCO-EP : prévalence et prédiction de l’embolie pulmonaire dans l’exacerbation de la broncho-pneumopathie obstructive chronique

INTRODUCTION

Patients suffering from chronic obstructive pulmonary disease (COPD) are often admitted to hospital with an exacerbation of their disease that manifests itself with an increase in cough and/or sputum, increased dyspnoea and sometimes chest pain. These episodes are most often attributed to an acute exacerbation of bronchial infection but the real cause is often unknown. COPD is considered a risk factor for pulmonary embolism (PE) and PE is part of the differential diagnosis of an acute exacerbation of COPD. However, the symptoms of these two conditions overlap to a considerable extent and the investigation of PE is often ignored in these patients. Therefore the true prevalence of PE in this situation is unknown. Nevertheless several small series suggest that up to 30% of patients seen as emergencies with exacerbations of COPD may have a deep vein thrombosis or PE. The aims of this study are therefore: 1. To evaluate the prevalence of PE in patients admitted as emergencies with exacerbations of COPD; and 2. To attempt to develop a prediction guide for PE in this population in order to identify the patients in whom PE should be investigated.

MATERIALS AND METHODS

600 consecutive patients admitted as emergencies with exacerbations of COPD will be included in a cross sectional study in three university hospitals (Geneva and Lausanne in Switzerland, and Amiens in France). Patients fulfilling the inclusion criteria will be investigated by a diagnostic algorithm appropriate for the study of PE, including D-dimer levels and, in those with abnormal results, ultrasonic scan of the deep veins of the legs and spiral CT scan. The patient characteristics on admission will be incorporated in a multivariate regression analysis in an attempt to identify the predictive factors for PE in these patients. The expected duration of the study is 24 months.

EXPECTED RESULTS

This study should determine the prevalence of PE in patients admitted as emergencies with exacerbations of COPD and therefore help decide when, and in which patients, a systematic search for PE should be undertaken.

Impaired fibrinolytic potential related to elevated ?1-proteinase inhibitor levels in patients with pulmonary thromboembolism

The contribution of neutrophil leukocyte elastase (NE) to in vivo thrombolysis is still an open question. The present study examines the impact of variable levels of alpha1-proteinase inhibitor (alpha1-PI) (the major plasma inhibitor of NE) on fibrinolysis within the setting of thromboembolic diseases. Blood samples were taken from 56 patients with pulmonary thromboembolism prior to treatment. alpha1-PI and alpha1-PI-NE complex were measured in the serum and plasma with immunoturbidimetric and enzyme-linked immunosorbent assay (ELISA) methods, respectively. The fibrinolytic potential [spontaneous, tissue-type plasminogen activator (tPA) induced, and plasmin induced] of the plasma was evaluated in vitro with turbidimetric clot lysis assay. Correlation analysis (Pearson product-moment correlation coefficient, r) of the turbidimetric lysis parameters and the blood levels of alpha1-PI and alpha1-PI-NE complex was carried out. Fibrinolysis is slower in clots prepared from plasma containing elevated levels of alpha1-PI and alpha1-PI-NE complex. The maximal turbidity of the plasma clots shows significant correlation with the alpha1-PI level (r=0.39, p=0.003) and the correlation of the maximal turbidity and the tPA-induced lysis time is also significant (r=0.77, p<0.001). The lysis time correlates with the plasma level of alpha1-PI-NE complex, if fibrinolysis is induced with tPA (r=0.37, p=0.02), but not with plasmin (r=0.19, p=0.4). Our study shows that in pulmonary thromboembolism elevated levels of alpha1-PI are associated with suppressed plasma fibrinolytic potential. This effect can be at least partially explained by the coarse fibrin network structure and retarded plasminogen activator-dependent fibrinolysis.

Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism

Overuse of the d-dimer to screen for possible pulmonary embolism (PE) can have negative consequences. This study derives and tests clinical criteria to justify not ordering a d-dimer. The test threshold was estimated at 1.8% using the method of Pauker and Kassirer. The PE rule-out criteria were derived from logistic regression analysis with stepwise backward elimination of 21 variables collected on 3148 emergency department patients evaluated for PE at 10 US hospitals. Eight variables were included in a block rule: Age < 50 years, pulse < 100 bpm, SaO(2) > 94%, no unilateral leg swelling, no hemoptysis, no recent trauma or surgery, no prior PE or DVT, no hormone use. The rule was then prospectively tested in a low-risk group (1427 patients from two hospitals initially tested for PE with a d-dimer) and a very low-risk group (convenience sample of 382 patients with chief complaint of dyspnea, PE not suspected). The prevalence of PE was 8% (95% confidence interval: 7-9%) in the low-risk group and 2% (1-4%) in the very low-risk group on longitudinal follow-up. Application of the rule in the low-risk and very low-risk populations yielded sensitivities of 96% and 100% and specificities of 27% and 15%, respectively. The prevalence of PE in those who met the rule criteria was 1.4% (0.5-3.0%) and 0% (0-6.2%), respectively. The derived eight-factor block rule reduced the pretest probability below the test threshold for d-dimer in two validation populations, but the rule's utility was limited by low specificity.

Suspicion of pulmonary embolism in outpatients: nonspecific chest pain is the most frequent alternative diagnosis

OBJECTIVES

Several recent studies have focused on identifying clinical predictors of embolism. However, although pulmonary embolism is ruled out in 70-85% of the patients in whom it is suspected, data on the clinical characteristics and discharge diagnosis of such patients are scarce. Our aim was to evaluate whether clinical characteristics would allow predicting alternative diagnoses other than pulmonary embolism thereby ruling out venous thromboembolism.

DESIGN

Retrospective analysis.

SETTING

Emergency centres of two teaching and general hospitals.

SUBJECTS

A total of 1090 consecutive outpatients admitted for clinically suspected pulmonary embolism and a diagnosis established by a validated algorithm and a 3-month follow-up.

OUTCOMES

Discharge diagnoses of patients in whom pulmonary embolism was ruled out were identified and regrouped into two categories: (i) nonspecific chest pain and (ii) diagnosis other than pulmonary embolism. Predictive accuracy of clinical and laboratory variables for diagnosing nonspecific chest pain was assessed by univariate and multivariate analysis.

RESULTS

In patients without pulmonary embolism, nonspecific chest pain (parietal chest pain, chest pain of unknown origin and pleuritis) was the most frequent discharge diagnosis (n = 334, 31% of the entire cohort, 43% of the patients without pulmonary embolism). Other patients without pulmonary embolism had a wide variety of diagnoses, of which the most frequent were bronchopneumonia (6.0% of the entire cohort) and heart failure (5.2%). In the multivariate analysis, seven variables were strongly associated with nonspecific chest pain: younger age (below 40 years), female gender, respiratory rate below 20 min(-1), heart rate below 100 min(-1), and absence of recent immobilization, dyspnoea and haemoptysis. Two of the 24 patients in whom all those characteristics were present had pulmonary embolism (8%, 95% CI 3-22%).

CONCLUSIONS

The most frequent discharge diagnosis in emergency ward patients in whom pulmonary embolism is ruled out is nonspecific chest pain. A clinical model did not allow to predict nonspecific chest pain with enough accuracy to rule out pulmonary embolism without further testing. Whether a more precise characterization of chest pain might allow an accurate identification of such patients deserves further study.

Pulmonary thromboembolism in Asians/Pacific Islanders in the United States: analysis of data from the National Hospital Discharge Survey and the United States Bureau of the Census

PURPOSE

To assess the rate of diagnosis of deep venous thrombosis, pulmonary embolism, and venous thromboembolism; the incidence in hospitalized patients; and mortality from pulmonary embolism among Asians/Pacific Islanders in the United States.

METHODS

The number of patients discharged from hospitals with a diagnostic code for pulmonary embolism or deep venous thrombosis from 1990 through 1999 was obtained from the National Hospital Discharge Survey. Population estimates and deaths from pulmonary embolism from 1990 through 1998 were obtained from the United States Bureau of the Census.

RESULTS

Rate ratios of 10-year age-adjusted rates of diagnosis of deep venous thrombosis, pulmonary embolism, and venous thromboembolism comparing Asians/Pacific Islanders with whites and African Americans ranged from 0.16 to 0.21. Rate ratios comparing incidences in hospitalized patients ranged from 0.32 to 0.42. The age-adjusted rate ratio of mortality in "others" (which included Asians/Pacific Islanders) was 0.29 (95% confidence interval [CI]: 0.01 to 0.87) compared with whites and 0.14 (95% CI: 0.0 to 0.58) compared with African Americans.

CONCLUSION

Rates of deep venous thrombosis, pulmonary embolism, and venous thromboembolism; incidences in hospitalized patients; and the mortality rate from pulmonary embolism were markedly lower in Asians/Pacific Islanders than in whites and African Americans. Clinical assessment of the prior probability of venous thromboembolic disease at the bedside should probably be adjusted based on these ethnic differences.

Diagnosing pulmonary embolism in outpatients with clinical assessment, D-dimer measurement, venous ultrasound, and helical computed tomography: a multicenter management study

PURPOSE

To evaluate a diagnostic strategy for pulmonary embolism that combined clinical assessment, plasma D-dimer measurement, lower limb venous ultrasonography, and helical computed tomography (CT).

METHODS

A cohort of 965 consecutive patients presenting to the emergency departments of three general and teaching hospitals with clinically suspected pulmonary embolism underwent sequential noninvasive testing. Clinical probability was assessed by a prediction rule combined with implicit judgment. All patients were followed for 3 months.

RESULTS

A normal D-dimer level (<500 microg/L by a rapid enzyme-linked immunosorbent assay) ruled out venous thromboembolism in 280 patients (29%), and finding a deep vein thrombosis by ultrasonography established the diagnosis in 92 patients (9.5%). Helical CT was required in only 593 patients (61%) and showed pulmonary embolism in 124 patients (12.8%). Pulmonary embolism was considered ruled out in the 450 patients (46.6%) with a negative ultrasound and CT scan and a low-to-intermediate clinical probability. The 8 patients with a negative ultrasound and CT scan despite a high clinical probability proceeded to pulmonary angiography (positive: 2; negative: 6). Helical CT was inconclusive in 11 patients (pulmonary embolism: 4; no pulmonary embolism: 7). The overall prevalence of pulmonary embolism was 23%. Patients classified as not having pulmonary embolism were not anticoagulated during follow-up and had a 3-month thromboembolic risk of 1.0% (95% confidence interval: 0.5% to 2.1%).

CONCLUSION

A noninvasive diagnostic strategy combining clinical assessment, D-dimer measurement, ultrasonography, and helical CT yielded a diagnosis in 99% of outpatients suspected of pulmonary embolism, and appeared to be safe, provided that CT was combined with ultrasonography to rule out the disease.

CT venography in suspected pulmonary thromboembolism

Pulmonary embolism (PE) and deep venous thrombosis (DVT) are a continuum and are difficult to diagnose clinically. Combined CT venography and pulmonary angiography (CTVPA) is a single examination that combines multidetector CT pulmonary angiography (CTPA) and CT venography (CTV) of the abdomen, pelvis, and lower extremities, providing "one-stop shopping" for venous thromboembolism without additional venipuncture or i.v. contrast, and it adds only a few additional minutes to scanning time. CTVPA rapidly and accurately examines the deep veins, reveals the presence, absence, and extent of deep venous thrombosis, serves as a baseline, and helps guide patient management. Multiple investigators have reported a high degree of accuracy when CTV is compared with venous ultrasound. There are some pitfalls in image interpretation, especially with regard to mixing artifacts, and there are continuing controversies as to exactly which parts of the abdomen, pelvis, and legs should be scanned routinely, the ideal timing of CTV acquisition relative to contrast injection, and the slice thickness and gap, if any, that should be used.

Practical utility of clinical prediction rules for suspected acute pulmonary embolism in a large academic institution

INTRODUCTION

In an attempt to standardize clinicians' approach to the determination of pretest probability (PTP) in pulmonary embolism (PE), two simplified scoring models have recently been proposed. We sought to determine the utility of these algorithms in patients with suspected PE in a large, tertiary, academic medical center.

METHODS

We performed a retrospective analysis of 295 inpatients and outpatients from our institution who were evaluated for suspected PE. Pretest probability (PTP) was calculated using two previously formulated scoring systems by Wells et al. (Canadian score) and Wicki et al. (Geneva score). Our primary endpoint was the prevalence of PE within each strata of PTP.

RESULTS

The prevalence of pulmonary embolism in our cohort was 30%. The prevalence of PE in the low, intermediate and high PTP groups using the Canadian score was 15.3% (95% CI 9.5-23.7%), 34.8% (95% CI 27.9-42.4%), and 47.2% (95% CI 32.0-63.0), respectively. When compared with the low PTP group, the odds ratios of the likelihood of PE was 2.95 (95% CI 1.56-5.59) in the intermediate PTP group and 4.95 (95% CI 2.11-11.64) in the high PTP. The Wicki analysis was divided into "Geneva pure" and "Geneva presumed", where the fractional inspired oxygen concentration was known and presumed to have been sampled on room air, respectively. Neither of the Geneva scores showed statistical significance in the prevalence of PE among the PTP groups.

CONCLUSIONS

The Wells' clinical prediction score is easily applied and meaningfully risk stratifies patients with suspected PE. In our population, the Geneva score was less useful.

[Pulmonary embolism: analysis of cases without initial suspicion and sensitivity of three clinical models]

BACKGROUND AND OBJECTIVE

Pulmonary embolism (PE) is a frequent and severe condition. Although clinical models do exist, many patients are wrongly diagnosed. Our objective was to evaluate the clinical characteristics of patients with PE who are admitted at a hospital without initial clinical suspicion of it. We also evaluated the sensitivity of three clinical models in order to categorize the pre-test probability of PE.

PATIENTS AND METHOD

Retrospective review of clinical cases of PE diagnosed in a teaching hospital during one year. We compared the clinical features of patients whose PE was not initially suspected with those of patients in whom PE was a first diagnosis. The three clinical models were applied in all cases.

RESULTS

58 patients were identified. In 15 out of them (26%), PE was not an initial diagnosis. Patients without an initial PE suspicion were older, and previous surgery was less frequent among them. The clinical models exhibited sensitivities (60, 85, 89%) which were lower than those previously reported but higher than the doctor's initial clinical suspicion (74%). The models showed bad agreement between them (kappa = 0.06-0.1).

CONCLUSIONS

An initial misdiagnosis of PE is not justified by atypical clinical characteristics. The use of clinical models would improve the clinical suspicion.

Efficacy of alteplase thrombolysis for ED treatment of pulmonary embolism with shock

Our objective was to assess efficacy and tolerance of thrombolysis using 0.6 mg/kg of Alteplase in patients with massive pulmonary embolism defined as the association of a pulmonary embolism with shock. We retrospectively included 21 patients presenting with a massive pulmonary embolism confirmed by either scintigraphy or spiral computed tomography. Patients were treated on the basis of a standard rationale followed by thrombolysis with 0.6 mg/kg Alteplase over a period of 15 minutes. Hospital mortality, vital signs before and 2 hours after thrombolysis, and incidence of hemorrhagic events were recorded. Five patients (23.8%) died, 4 of these deaths occurred during the first 4 hours after hospital admission. Systolic and diastolic blood pressure (Sp02) were significantly improved 2 hours after the beginning of thrombolysis. Five minor hemorrhagic events occurred. This study demonstrates that for patients with pulmonary embolism and shock, a bolus treatment with Alteplase is potentially effective and well tolerated.

Misdiagnosis of pulmonary embolism in patients with allergic reaction — The importance of prior probability of disease

Because pulmonary embolism (PE) and its treatment carry substantial risk of morbidity and mortality, accurate diagnosis is essential. We report two cases with allergic reactions, in which PE was suggested by routine ECG and D-dimer elevation and strengthened by spiral CT. Therapy with low-molecular-weight heparin was initiated and long-term anticoagulation was considered. As their histories did not reveal any predisposing factor to PE, the cases were re-evaluated. Elevation of D-dimer was now attributed to allergic reaction, ECG abnormalities were considered as constitutional, and findings from spiral CT attributed to breathing artifacts and partial-volume effects. The diagnosis of PE was therefore rejected and anticoagulant treatment discontinued without sequelae. These cases show the importance of determining clinical probability before ordering further diagnostic tests and critical interpretation of test results suggestive of PE, based on prior probability of the disease.

V/Q-Scanning/SPECT for the Diagnosis of Pulmonary Embolism

Pulmonary embolism (PE) is visualized indirectly by perfusion (Q) scanning as a parenchymal defect related to the embolized artery, and is confirmed by combined ventilation (V) scanning, showing a normal regional ventilation. Based on its principle of detection, V/Q scanning is able to show even small emboli and this ability is enhanced by SPECT. Compared to angiography, V/Q scanning seems to be burdened with low specificity, whereas its sensitivity is sufficiently high. Correlation of V/Q scanning with single-slice CT is comparable with that with angiography. The positive predictive value of V/Q scanning cannot be assessed by the reference standard angiography or by single-slice CT because both have turned out to be inadequate. Correlation of V/Q scanning with high-resolution CT is very promising, revealing high sensitivity as well as specificity of V/Q scanning, but this needs further evaluation in larger studies. Nevertheless, the use of V/Q scanning as a one-step diagnostic approach to PE is unrestricted in patients with normal chest radiograph, whereas V/Q scanning in combination with spiral CT is recommended in patients with abnormal chest radiograph. The negative predictive value of V/Q scanning for recurrent PE is unsurpassed high and by this, V/Q scanning tends to be used primarily to exclude rather than confirm PE.

Comparison of diagnostic accuracies in outpatients and hospitalized patients of D-dimer testing for the evaluation of suspected pulmonary embolism

BACKGROUND

The ability of various D-dimer assays to exclude the diagnosis of thromboembolic diseases is controversial. We examined the diagnostic accuracy of two D-dimer methods in hospitalized patients and outpatients.

METHODS

We studied consecutive patients for whom D-dimer testing was ordered for investigation of suspected pulmonary embolism. We measured D-dimer by an ELISA (VIDAS D-dimer) and an enhanced microlatex immunoassay method (Diagnostica Stago STA Liatest D-di). Patient diagnoses were based on imaging studies or, when these were not performed, on follow-up by review of medical records 3 months later.

RESULTS

We examined 233 hospitalized patients and 234 outpatients with a mean age of 58 years (range, 1-92 years) and a female-to-male ratio of 1.4 to 1. Thromboembolism was present in 8% of outpatients and 12% of hospitalized patients. In outpatients, the negative predictive values were 98% [95% confidence interval (CI), 93-100%] and 99% (94-100%) for the microlatex and ELISA methods, respectively, at the recommended cutoffs. Areas under the ROC curves were similar for the two methods [0.77 (95% CI, 0.67-0.87) and 0.81 (0.73-0.89), respectively]. By contrast, in hospitalized patients, the confidence intervals for the areas under the ROC curves included 0.5 [0.60 (95% CI, 0.50-0.71) and 0.56 (0.44-0.67)].

CONCLUSIONS

For hospitalized patients, in contrast to outpatients, the diagnostic accuracy of D-dimer testing for pulmonary embolism is poor in a tertiary care setting, presumably reflecting thrombosis and comorbidities, other than pulmonary embolism, that increase the D-dimer concentrations in these patients. The patient population studied appears more important than assay method in studies of the diagnostic accuracy of D-dimer testing.

The utility of pretest probability assessment in patients with clinically suspected venous thromboembolism

The assessment of pretest probability (PTP), with stratification into low-, intermediate- and high-risk groups is an essential initial step in the current diagnostic management of patients with suspected venous thromboembolism (VTE). In combination with additional information, it reduces the need for initial and supplementary imaging, and allows considerable refinement of the posterior probability of VTE following non-invasive imaging. PTP may be assessed either empirically or by using various decision rules or scoring systems, the best known of which are the simplified Wells scores for suspected deep vein thrombosis (DVT) and pulmonary embolism (PE), and the Geneva score for suspected PE. Each of these approaches shows similar directional and categorical accuracy, and has been validated as facilitating clinically useful classification of the PTP, although an overview of data suggests that fewer patients tend to be classified as low PTP when assessed empirically. This group is the most important to identify, as several outcome studies have shown that imaging and treatment are safely obviated in outpatients with suspected DVT or PE who have a low PTP in combination with negative d-dimer testing, a subgroup accounting for up to half of all patients studied. Hence, while probably not of critical importance, the explicit approach offered by scoring systems might be preferred over empirical assessment, particularly when used by more junior staff.

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 probability evaluation models in patients with pulmonary thromboembolism]

BACKGROUND

The evaluation of the clinical probability (CP) of pulmonary thromboembolism (PTE) is useful in patients with suspected PTE.

METHOD

We assessed the CP of PTE using 3 different models (described by Miniati et al., Wells et al. and Wicki et al.) in a series of 154 patients with PTE.

RESULTS

A high CP and a low CP were present in 11.7%, 39% and 14.3%, and in 0.6%, 0% and 1.9% of patients with PTE according to the first, second and third models, respectively. The frequency of high CP was not significantly different between patients older or younger than 70 years, between both sexes, nor between patients with or without cardiopulmonary disease. There was, however, a significantly lower frequency of high CP, according to the second model, in patients older than 70 years (31.1% vs 50%, p = 0.03).

CONCLUSIONS

The CP evaluation models studied are comparable. A low CP makes highly improbable a diagnosis of PTE. Only up to approximately one third of patients with PTE hare a high CP.

Laboratory tests in the diagnosis of pulmonary embolism

The diagnosis of pulmonary embolism (PE) requires objective testing. However, all imaging techniques have their own limitations and costs and cannot be performed in every patient with suspected PE. After decades of unfruitful research, several laboratory tests have been evaluated for suspected PE, the most promising being the D-dimer test. As a general rule, the specificity of D-dimers is too low to confirm PE. Conversely, several (but not all) D-dimer assays have a high sensitivity for diagnosing PE. Outcome studies indicate that the Vidas D-dimer and SimpliRED D-dimer can be used safely to withdraw anticoagulation when the pretest probability of PE is low (SimpliRED) or when it is low or moderate (Vidas). These results may however not apply to other D-dimer assays and clinicians should know the characteristics of the test used in their hospital. Blood gas analysis does not have sufficient sensitivity and specificity to confirm or exclude PE, but it may be used to evaluate the clinical probability of PE before other testing is done. The diagnostic value of the alveolar dead space fraction in patients with suspected PE is currently investigated. Initial data suggest that it needs to be combined with a D-dimer test to safely exclude PE. Brain natriuretic peptide and cardiac troponin have limited usefulness for diagnosing PE, but both tests may identify patients with a poor prognosis, in whom more aggressive treatment may be warranted.

Diagnosis of pulmonary embolism: when is imaging needed?

Recent advances in the management of patients with suspected pulmonary embolism have improved diagnostic accuracy and made management algorithms safer and more accessible. Ongoing clinical trials are evaluating whether these diagnostic processes can be made even simpler and less expensive. It is now possible to identify low-risk patients with suspected pulmonary embolism in whom imaging procedures can be avoided altogether.

Venous thromboembolism in intensive care patients

Venous thromboembolism frequently complicates the management of patients with severe medical and surgical illnesses. Because the diagnosis of VTE is especially challenging in critically ill patients, the focus of intensivists should be on characterization of risk factors and the appropriate choice of VTE prophylaxis. LDUH or LMHW is the preferred choice for VTE prophylaxis in ICU patients. Mechanical methods of prophylaxis should be reserved for patients with a high risk for bleeding. The effectiveness of mechanical methods and of combined strategies of prevention and the clinically important outcomes of therapy need to be explored further in critically ill patients. Few diagnostic strategies have been assessed in ICU patients with suspected PE. Ventilation-perfusion lung scans remain a pivotal diagnostic test but retain the same limitations in critically ill patients as seen in other patient populations. Newer noninvasive techniques, such as spiral CT associated with imaging of the extremities, are gaining more wide-spread use, but, thus far, pulmonary angiography remains the most reliable technique to confirm or exclude PE in patients with respiratory failure. A consensus must be reached regarding the most appropriate combination of tests for adequate and cost-effective diagnosis of VTE. Further investigation of diagnostic strategies that include adequate consideration of clinical diagnosis using standardized models and noninvasive imaging are warranted.

A structured clinical model for predicting the probability of pulmonary embolism

PURPOSE

To develop a structured model to predict the clinical probability of pulmonary embolism.

METHODS

We studied 1,100 consecutive patients with suspected pulmonary embolism in whom a definite diagnosis had been established. We used logistic regression analysis to estimate the probability of pulmonary embolism based on patients' clinical characteristics; the probability was categorized as low (< or = 10%), intermediate (>10%, < or = 50%), moderately high (>50%, < or = 90%), or high (>90%).

RESULTS

The overall prevalence of pulmonary embolism was 40% (n = 440). Ten characteristics were associated with an increased risk of pulmonary embolism (male sex, older age, history of thrombophlebitis, sudden-onset dyspnea, chest pain, hemoptysis, electrocardiographic signs of acute right ventricular overload, radiographic signs of oligemia, amputation of the hilar artery, and pulmonary consolidation suggestive of infarction), and five were associated with a decreased risk (prior cardiovascular or pulmonary disease, high fever, pulmonary consolidation other than infarction, and pulmonary edema on the chest radiograph). With this model, 432 patients (39%) were rated a low probability, of whom 19 (4%) had pulmonary embolism; 283 (26%) were rated an intermediate probability, of whom 62 (22%) had pulmonary embolism; 72 (7%) were rated a moderately high probability, of whom 53 (74%) had pulmonary embolism; and 313 (28%) were rated a high probability, of whom 306 (98%) had pulmonary embolism.

CONCLUSION

This prediction model may be useful for estimating the probability of pulmonary embolism before obtaining definitive test results.

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.

Does this patient have acute cholecystitis?

CONTEXT

Although few patients with acute abdominal pain will prove to have cholecystitis, ruling in or ruling out acute cholecystitis consumes substantial diagnostic resources.

OBJECTIVE

To determine if aspects of the history and physical examination or basic laboratory testing clearly identify patients who require diagnostic imaging tests to rule in or rule out the diagnosis of acute cholecystitis.

DATA SOURCES

Electronic search of the Science Citation Index, Cochrane Library, and English-language articles from January 1966 through November 2000 indexed in MEDLINE. We also hand-searched Index Medicus for 1950-1965, and scanned references in identified articles and bibliographies of prominent textbooks of physical examination, surgery, and gastroenterology. To identify relevant articles appearing since the comprehensive search, we repeated the MEDLINE search in July 2002.

STUDY SELECTION

Included studies evaluated the role of the history, physical examination, and/or laboratory tests in adults with abdominal pain or suspected acute cholecystitis. Studies had to report data from a control group found not to have acute cholecystitis. Acceptable definitions of cholecystitis included surgery, pathologic examination, hepatic iminodiacetic acid scan or right upper quadrant ultrasound, or clinical course consistent with acute cholecystitis and no evidence for an alternate diagnosis. Studies of acalculous cholecystitis were included. Seventeen of 195 identified studies met the inclusion criteria.

DATA EXTRACTION

Two authors independently abstracted data from the 17 included studies. Disagreements were resolved by discussion and consensus with a third author.

DATA SYNTHESIS

No clinical or laboratory finding had a sufficiently high positive likelihood ratio (LR) or low negative LR to rule in or rule out the diagnosis of acute cholecystitis. Possible exceptions were the Murphy sign (positive LR, 2.8; 95% CI, 0.8-8.6) and right upper quadrant tenderness (negative LR, 0.4; 95% CI, 0.2-1.1), though the 95% CIs for both included 1.0. Available data on diagnostic confirmation rates at laparotomy and test characteristics of relevant radiological investigations suggest that the diagnostic impression of acute cholecystitis has a positive LR of 25 to 30. Unfortunately, the available literature does not identify the specific combinations of clinical and laboratory findings that presumably account for this diagnostic success.

CONCLUSIONS

No single clinical finding or laboratory test carries sufficient weight to establish or exclude cholecystitis without further testing (eg, right upper quadrant ultrasound). Combinations of certain symptoms, signs, and laboratory results likely have more useful LRs, and presumably inform the diagnostic impressions of experienced clinicians. Pending further research characterizing the pretest probabilities associated with different clinical presentations, the evaluation of patients with abdominal pain suggestive of cholecystitis will continue to rely heavily on the clinical gestalt and diagnostic imaging.

Comparison of two clinical prediction rules and implicit assessment among patients with suspected pulmonary embolism

PURPOSE

Two prediction rules for pulmonary embolism have been described recently: the Wells' rule, which was derived from both outpatients and inpatients, and which includes a subjective element; and the Geneva rule, which is entirely standardized and is suitable only for emergency department patients. We compared the predictive accuracy and the concordance of the two methods, as well as the Geneva score overridden by implicit clinical judgment.

SUBJECTS AND METHODS

We studied 277 consecutive patients admitted to the emergency departments of three teaching hospitals. Clinical probability was assessed prospectively with the Geneva score and the Geneva score overridden by implicit clinical judgment in case of a disagreement. The Wells' score was calculated retrospectively.

RESULTS

The three methods classified similar proportions of patients as having a low (53% to 58% of patients), intermediate (37% to 41% of patients), or high (4% to 10% of patients) probability of pulmonary embolism. The actual frequencies of pulmonary embolism in each category were also similar (5% to 13% in the low, 38% to 40% in the intermediate, and 67% to 91% in the high clinical probability categories). Receiver operating characteristic curve analysis showed no difference between the two prediction rules, but the Geneva score overridden by implicit evaluation had a marginally higher accuracy. Concordance between the two prediction rules was fair (kappa coefficient = 0.43). Clinicians disagreed with the Geneva score in 21% of patients (n = 57).

CONCLUSIONS

The two prediction rules had a similar predictive accuracy for pulmonary embolism among emergency department patients. The Geneva rule appears to be more accurate when combined with clinical judgment, although it does not apply to inpatients.

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.

The natural history of venous thromboembolism: impact on ventilation/perfusion scan reporting

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are separate but related aspects of the same dynamic disease process known as venous thromboembolism (VTE). Recent community studies have shown that VTE is a major health issue for the developed world, with at least 201,000 new cases each year in the United States, comprising 107,000 with DVT and 94,000 with PE. A quarter of PE cases die within 7 days, some so rapidly that treatment or intervention is impossible. Despite the availability of heparin prophylaxis, the annual incidence of VTE has remained constant at 1 event per 1,000 person-years since 1979 but reaches 1 event per 100 person-years for the over-85-year-olds. The most important risk factors for VTE are hemostatic and environmental. The recent discoveries of factor V Leiden, prothrombin 20210A, and high concentrations of factor VIII have highlighted the increasing importance of a genetic predisposition to thrombophilia. Acquired hemostatic factors include pregnancy and the puerperium, oral contraception, hormone-replacement therapy, malignant tumors, and antiphospholipid syndromes. Important environmental risk factors include hospitalization with previous surgery or trauma, confinement in a care facility, neurologic disease or paraplegia after stroke, current or recent central venous catheter or transvenous pacemaker, and long airplane flights. Internists may be confused about the risk of PE after ventilation/perfusion (VQ) imaging. This may well arise from their use of the relative risk of PE after a low-probability category scan rather than the absolute risk obtained by incorporating the PE prevalence for their particular patient in the risk analysis. Ideally, personal communication with an experienced referring physician provides this clinical information for nuclear medicine. Diagnostic tools or checklists can be used as an alternative. A general knowledge of the natural history of VTE will encourage the nuclear medicine physician to provide an appropriate clinical signal to complement VQ categorical analysis. Combination of these 2 dynamic elements of the art and science of VQ scan reporting-the clinical pretest probability of PE and lung scan category-will permit an accurate prediction of the absolute risk of PE posttest.

[When to suspect pulmonary embolism in a patient with deep venous thrombosis?]

The approach to take in trying to establish or disprove a diagnosis of pulmonary embolism in the presence of deep vein thrombosis is the subject of some controversy nowadays. Systematic perfusion lung scan can be proposed, given the mediocre specificity of the clinical symptoms of embolism or the high frequency of asymptomatic pulmonary embolism. This strategy, however, is not validated in terms of cost-efficacy. In practical terms, favourable evolution and the low rate of recurrent embolism observed with a well executed anticoagulant treatment pleads against systematic scintigraphy. Because of its moderate sensitivity, systematic echocardiography probably should not be an element of the assessment of asymptomatic pulmonary embolism. The advent of spiral CT scan in the management of such patients could however make it necessary to reconsider this position, by allowing complete venous and pulmonary examination in thrombo-embolic disease.

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.