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

Intermediate-Risk and High-Risk Pulmonary Embolism: Recognition and Management: Cardiology Clinics: Cardiac Emergencies

Pulmonary embolism (PE) is the third most common cause of cardiovascular death. Every specialty of medical practitioner will encounter PE in their patients, and should be prepared to employ contemporary strategies for diagnosis and initial risk-stratification. Treatment of PE is based on risk-stratification, with anticoagulation for all patients, and advanced modalities including systemic thrombolysis, catheter-directed therapies, and mechanical circulatory supports utilized in a manner paralleling PE severity and clinical context.

How to Combat Over-Testing for Patients Suspected of Pulmonary Embolism: A Narrative Review

The diagnosis of PE remains difficult in 2023 because the signs and symptoms are not sensible nor specific. The consequences of potential diagnostic errors can be dramatic, whether by default or by excess. Furthermore, the achievement of a simple diagnostic strategy, based on clinical probability assessment, D-dimer measurement and computed tomography pulmonary angiography (CTPA) leads to a new challenge for PE diagnosis: over-testing. Indeed, since the 2000s, the wide availability of CTPA resulted in a major increase in investigations with a mod I confirm erate increase in PE diagnosis, without any notable improvement in patient outcomes. Quite the contrary, the complications of anticoagulation for PE increased significantly, and the long-term consequences of imaging diagnostic radiation is an important concern, especially the risk of breast cancer for young women. As a result, several strategies have been proposed to fight over-testing. They are mostly based on defining a subgroup of patients for whom no specific exam should be required to rule-out PE and adjusting the D-dimer cutoff to allow the exclusion of PE without performing CTPA. This narrative review presents the advantages and limitations of these different strategies as well as the perspective in PE diagnosis.

New cut-off point for D-dimer in the diagnosis of pulmonary embolism during pregnancy

Background

Considering that pulmonary embolism (PE) is one of the leading causes of mortality among pregnant women and that the D-dimer level in pregnancy can be highly fluctuating, a new and reliable D-dimer reference value is essential to identifying PE in this group of patients. Hence, the present study aimed to evaluate the diagnostic effect of D-dimer testing in pregnant women with suspected PE.

Methods

This study recruited 100 women with confirmed pregnancy or six weeks after delivery or abortion with suspected PE symptoms. Wells criteria, D-dimer values, and pregnancy trimesters were recorded. Definitive PE results were obtained using multidetector computed tomography (MDCT) or pulmonary ventilation/perfusion scans.

Results

D-dimer cut-off point in PE diagnosis was higher than 1,447 mg/L [sensitivity, 87.5%; specificity, 63.04%; area under the curve (AUC)=0.735; P=0.003]. In addition, the combination of Wells criteria with the D-dimer test indicated that the cut-off points of D-dimer in PE likely and unlikely women were 1,962 and 1,447 mg/L, respectively, and had acceptable and significant diagnostic value in PE detection. In addition, the diagnostic value of D-dimer in pregnancy trimesters was not found to be significant (P>0.05).

Conclusion

The new cut-off points of 1,447 and 1,962 mg/L were determined for D-dimer in pregnant women with likely and unlikely PE, respectively. Moreover, the new cut-off points in the first and second trimesters of pregnancy were 1,701 mg/L and 1,451 mg/L, respectively, which indicated no statistically acceptable diagnostic value.

High-Risk Chief Complaints I: Chest Pain-The Big Three (an Update)

Nontraumatic chest pain is a frequent concern of emergency department patients, with causes that range from benign to immediately life threatening. Identifying those patients who require immediate/urgent intervention remains challenging and is a high-risk area for emergency medicine physicians where incorrect or delayed diagnosis may lead to significant morbidity and mortality. This article focuses on the 3 most prevalent diagnoses associated with adverse outcomes in patients presenting with nontraumatic chest pain, acute coronary syndrome, thoracic aortic dissection, and pulmonary embolism. Important aspects of clinical evaluation, diagnostic testing, treatment, and disposition and other less common causes of lethal chest pain are also discussed.

D-dimer: Preanalytical, analytical, postanalytical variables, and clinical applications

D-dimer is a soluble fibrin degradation product deriving from the plasmin-mediated degradation of cross-linked fibrin. D-dimer can hence be considered a biomarker of activation of coagulation and fibrinolysis, and it is routinely used for ruling out venous thromboembolism (VTE). D-dimer is increasingly used to assess the risk of VTE recurrence and to help define the optimal duration of anticoagulation treatment in patients with VTE, for diagnosing disseminated intravascular coagulation, and for screening medical patients at increased risk of VTE. This review is aimed at (1) revising the definition of D-dimer; (2) discussing preanalytical variables affecting the measurement of D-dimer; (3) reviewing and comparing assay performance and some postanalytical variables (e.g. different units and age-adjusted cutoffs); and (4) discussing the use of D-dimer measurement across different clinical settings.

Pregnancy-Adapted YEARS Algorithm for Diagnosis of Suspected Pulmonary Embolism

BACKGROUND

Pulmonary embolism is one of the leading causes of maternal death in the Western world. Because of the low specificity and sensitivity of the d-dimer test, all pregnant women with suspected pulmonary embolism undergo computed tomographic (CT) pulmonary angiography or ventilation-perfusion scanning, both of which involve radiation exposure to the mother and fetus. Whether a pregnancy-adapted algorithm could be used to safely avoid diagnostic imaging in pregnant women with suspected pulmonary embolism is unknown.

METHODS

In a prospective study involving pregnant women with suspected pulmonary embolism, we assessed three criteria from the YEARS algorithm (clinical signs of deep-vein thrombosis, hemoptysis, and pulmonary embolism as the most likely diagnosis) and measured the d-dimer level. Pulmonary embolism was ruled out if none of the three criteria were met and the d-dimer level was less than 1000 ng per milliliter or if one or more of the three criteria were met and the d-dimer level was less than 500 ng per milliliter. Adaptation of the YEARS algorithm for pregnant women involved compression ultrasonography for women with symptoms of deep-vein thrombosis; if the results were positive (i.e., a clot was present), CT pulmonary angiography was not performed. All patients in whom pulmonary embolism had not been ruled out underwent CT pulmonary angiography. The primary outcome was the incidence of venous thromboembolism at 3 months. The secondary outcome was the proportion of patients in whom CT pulmonary angiography was not indicated to safely rule out pulmonary embolism.

RESULTS

A total of 510 women were screened, of whom 12 (2.4%) were excluded. Pulmonary embolism was diagnosed in 20 patients (4.0%) at baseline. During follow-up, popliteal deep-vein thrombosis was diagnosed in 1 patient (0.21%; 95% confidence interval [CI], 0.04 to 1.2); no patient had pulmonary embolism. CT pulmonary angiography was not indicated, and thus was avoided, in 195 patients (39%; 95% CI, 35 to 44). The efficiency of the algorithm was highest during the first trimester of pregnancy and lowest during the third trimester; CT pulmonary angiography was avoided in 65% of patients who began the study in the first trimester and in 32% who began the study in the third trimester.

CONCLUSIONS

Pulmonary embolism was safely ruled out by the pregnancy-adapted YEARS diagnostic algorithm across all trimesters of pregnancy. CT pulmonary angiography was avoided in 32 to 65% of patients. (Funded by Leiden University Medical Center and 17 other participating hospitals; Artemis Netherlands Trial Register number, NL5726.).

Multicenter Evaluation of the YEARS Criteria in Emergency Department Patients Evaluated for Pulmonary Embolism

BACKGROUND

It may be possible to safely rule out pulmonary embolism (PE) in patients with low pretest probability (PTP) using a higher than standard D-dimer threshold. The YEARS criteria, which include three questions from the Wells PE score to identify low-PTP patients and a variable D-dimer threshold, was recently shown to decrease the need for imaging to rule out PE by 14% in a multicenter study in the Netherlands. However, the YEARS approach has not been studied in the United States.

METHODS

This study was a prospective, observational study of consecutive adult patients evaluated for PE in 17 U.S. emergency departments. Prior to diagnostic testing, we collected the YEARS criteria: "Does the patient have clinical signs or symptoms of DVT?" "Does the patient have hemoptysis?" "Are alternative diagnoses less likely than PE?" with YEARS (+) being any "yes" response. A negative D-dimer was <1000 mg/dL for YEARS (-) patients and <500 mg/dL for YEARS (+) patients. We calculated test characteristics and used Fisher's exact test to compare proportions of patients who would have been referred for imaging and patients who would have had PE "missed."

RESULTS

Of 1,789 patients, 84 (4%) had PE, 1,134 (63%) were female, 1,038 (58%) were white, and mean (±SD) age was 48 (±16) years. Using the standard D-dimer threshold, 940 (53%) would not have had imaging, with two (0.2%, 95% confidence interval [CI] = 0.02%-0.60%) missed PE. Using YEARS adjustment, 1,204 (67%, 95% CI = 65%-69%) would not have been referred for imaging, with six (0.5%, 95% CI = 0.18%-1.1%) missed PE, and using "alternative diagnoses less likely than PE" adjustment, 1,237 (69%, 95% CI = 67%-71%) would not have had imaging with six (0.49%, 95% CI = 0.18%-1.05%) missed PE. Sensitivity was 97.6% (95% CI = 91.7%-99.7%) for the standard threshold and 92.9% (95% CI = 85%-97%) for both adjusted thresholds. Negative predictive value (NPV) was nearly 100% for all approaches.

CONCLUSIONS

D-dimer adjustment based on PTP may result in a reduced need for imaging to evaluate possible PE, with some additional missed PE but no decrease in NPV.

Ruling out Pulmonary Embolism in Patients with High Pretest Probability

Introduction

The American College of Emergency Physicians guidelines recommend more aggressive workup beyond imaging alone in patients with a high pretest probability (PTP) of pulmonary embolism (PE). However, the ability of multiple tests to safely rule out PE in high PTP patients is not known. We sought to measure the ability of negative computed tomography pulmonary angiography (CTPA) along with negative D-dimer to rule out PE in these high-risk patients.

Methods

We analyzed data from a previous prospective observational study conducted in 12 emergency departments (ED). Wells score criteria were entered by providers before final PE testing. PE was diagnosed by imaging on the index ED visit, or within 45 days, demonstrating either PE or deep vein thrombosis (DVT), or if the patient died of PE during the 45-day, follow-up period. Testing threshold was set at 1.8%.

Results

A total of 7,940 patients were enrolled and tested for PE, and 257 had high PTP (Wells >6). Sixteen of these high-risk patients had negative CTPA and negative D-dimer, of whom two were positive for PE (12.5% [95% confidence interval {2.2%–40.0%}]). One of these patients had a DVT on CT venogram and the other was diagnosed at follow-up.

Conclusion

Our analysis suggests that in patients with high PTP of PE, neither negative CTPA by itself nor a negative CTPA plus a negative D-dimer are sufficient to rule out PE. More aggressive workup strategies may be required for these patients.

Comparison of clinical probability-adjusted D-dimer and age-adjusted D-dimer interpretation to exclude venous thromboembolism

Two new strategies for interpreting D-dimer results have been proposed: i) using a progressively higher D-dimer threshold with increasing age (age-adjusted strategy) and ii) using a D-dimer threshold in patients with low clinical probability that is twice the threshold used in patients with moderate clinical probability (clinical probability-adjusted strategy). Our objective was to compare the diagnostic accuracy of age-adjusted and clinical probability-adjusted D-dimer interpretation in patients with a low or moderate clinical probability of venous thromboembolism (VTE). We performed a retrospective analysis of clinical data and blood samples from two prospective studies. We compared the negative predictive value (NPV) for VTE, and the proportion of patients with a negative D-dimer result, using two D-dimer interpretation strategies: the age-adjusted strategy, which uses a progressively higher D-dimer threshold with increasing age over 50 years (age in years × 10 µg/L FEU); and the clinical probability-adjusted strategy which uses a D-dimer threshold of 1000 µg/L FEU in patients with low clinical probability and 500 µg/L FEU in patients with moderate clinical probability. A total of 1649 outpatients with low or moderate clinical probability for a first suspected deep vein thrombosis or pulmonary embolism were included. The NPV of both the clinical probability-adjusted strategy (99.7%) and the age-adjusted strategy (99.6%) were similar. However, the proportion of patients with a negative result was greater with the clinical probability-adjusted strategy (56.1% vs, 50.9%; difference 5.2%; 95% CI 3.5% to 6.8%). These findings suggest that clinical probability-adjusted D-dimer interpretation is a better way of interpreting D-dimer results compared to age-adjusted interpretation.

D-dimer Interval Likelihood Ratios for Pulmonary Embolism

OBJECTIVE

The objective was to estimate D-dimer interval likelihood ratios (iLRs) for diagnosing pulmonary embolism (PE).

METHODS

The authors used pooled patient-level data from five PE diagnostic management studies to estimate iLRs for the eight D-dimer intervals with boundaries 250, 500, 750, 1,000, 1,500, 2,500, and 5,000 ng/mL. Logistic regression was used to fit the data so that an interval increase corresponds to increasing the likelihood ratio by a constant factor.

RESULTS

The iLR for the D-dimer interval 1,000-1,499 ng/mL was essentially 1.0 (0.98 with 95% confidence interval [CI] = 0.82-1.18). In the logistic regression model, the constant between-interval factor was 2.0 (95% CI = 1.9-2.1). Using these iLR estimates, if the pre-D-dimer probability of PE is 15%, only a D-dimer less than 500 ng/mL will result in a posttest probability below 3%; if the pretest probability is 5%, the threshold for a "negative" D-dimer is 1,000 ng/mL.

CONCLUSIONS

A decision strategy based on these approximate iLRs agrees with several published strategies.

Pulmonary embolism: the diagnosis, risk-stratification, treatment and disposition of emergency department patients

The diagnosis or exclusion of pulmonary embolism (PE) remains challenging for emergency physicians. Symptoms can be vague or non-existent, and the clinical presentation shares features with many other common diagnoses. Diagnostic testing is complicated, as biomarkers, like the D-dimer, are frequently false positive, and imaging, like computed tomography pulmonary angiography, carries risks of radiation and contrast dye exposure. It is therefore incumbent on emergency physicians to be both vigilant and thoughtful about this diagnosis. In recent years, several advances in treatment have also emerged. Novel, direct-acting oral anticoagulants make the outpatient treatment of low risk PE easier than before. However, the spectrum of PE severity varies widely, so emergency physicians must be able to risk-stratify patients to ensure the appropriate disposition. Finally, PE response teams have been developed to facilitate rapid access to advanced therapies (e.g., catheter directed thrombolysis) for patients with high-risk PE. This review will discuss the clinical challenges of PE diagnosis, risk stratification and treatment that emergency physicians face every day.

Improving appropriate use of pulmonary computed tomography angiography by increasing the serum D-dimer threshold and assessing clinical probability

OBJECTIVE

To determine whether the implementation of an increased D-dimer threshold value and clinical probability assessment increases the prevalence of pulmonary embolism (PE) in patients undergoing pulmonary computed tomography angiography (PCTA) in an Emergency Department setting.

METHODS

A retrospective review of all patients undergoing PCTA during 2 separate 12-month intervals, 1 before the implementation of an increased D-dimer threshold and recommendation for formal clinical probability assessment and the other after regional implementation. The primary outcome measure was the prevalence of acute PE in each of the samples.

RESULTS

After the implementation of the increased D-dimer threshold and recommendation for formal clinical probability assessment, the prevalence of PE detected by PCTA increased from 4.7% to 11.7% (p < 0.001). Among all PCTAs performed after the new guidelines were promulgated, 8.6% were still performed on patients who had serum D-dimer values lower than the threshold of 1.0 µg/mL. Despite the recommendation for formal clinical probability assessment before ordering a PCTA, only 4% of patients had a formal clinical probability assessment recorded in their electronic medical record.

CONCLUSION

The implementation of an increased D-dimer threshold value increased the prevalence of PE in patients undergoing PCTA in an Emergency Department setting, but more consistent application of clinical probability assessment remains an elusive target.

A simple decision rule including D-dimer to reduce the need for computed tomography scanning in patients with suspected pulmonary embolism

BACKGROUND

An 'unlikely' clinical decision rule with a negative D-dimer result safely excludes pulmonary embolism (PE) in 30% of presenting patients. We aimed to simplify this diagnostic approach and to increase its efficiency.

METHODS

Data for 723 consecutive patients with suspected PE were analyzed (prevalence of PE, 22%). After constructing a logistic regression model with the D-dimer test result and items from the Wells' score, we identified the most prevalent combinations of influential items and selected new D-dimer positivity thresholds. The performance was separately validated with data from 2785 consecutive patients with suspected PE.

RESULTS

Three Wells items significantly added incremental value to the D-dimer test: hemoptysis, signs of deep vein thrombosis and 'PE most likely'. Based on the most frequent combinations of these three items, we identified two groups: (i) none of these three items positive (41%); (ii) one or more of these items positive (59%). When applying a 1000 μg/L D-dimer threshold in group 1 and 500 μg/L in group 2, PE could be excluded without CT scanning in 36%, at a false-negative rate of 1.2% (95%, 0.04-3.3%). In the validation set, these proportions were 46% and 1.9% (95% CI, 1.2-2.7%), respectively. Using the conventional Wells score with a normal D-dimer result, these rates were, respectively, 22% and 0.6% (95% CI, 0.10-2.4%).

CONCLUSION

Combining Wells items with the D-dimer test resulted in a simplified decision rule, which reduces the need for CT scanning in patients with suspected PE. A prospective validation is required before it can be implemented in clinical practice.

A systematic review of studies comparing diagnostic clinical prediction rules with clinical judgment

Background

Diagnostic clinical prediction rules (CPRs) are developed to improve diagnosis or decrease diagnostic testing. Whether, and in what situations diagnostic CPRs improve upon clinical judgment is unclear.

Methods and Findings

We searched MEDLINE, Embase and CINAHL, with supplementary citation and reference checking for studies comparing CPRs and clinical judgment against a current objective reference standard. We report 1) the proportion of study participants classified as not having disease who hence may avoid further testing and or treatment and 2) the proportion, among those classified as not having disease, who do (missed diagnoses) by both approaches. 31 studies of 13 medical conditions were included, with 46 comparisons between CPRs and clinical judgment. In 2 comparisons (4%), CPRs reduced the proportion of missed diagnoses, but this was offset by classifying a larger proportion of study participants as having disease (more false positives). In 36 comparisons (78%) the proportion of diagnoses missed by CPRs and clinical judgment was similar, and in 9 of these, the CPRs classified a larger proportion of participants as not having disease (fewer false positives). In 8 comparisons (17%) the proportion of diagnoses missed by the CPRs was greater. This was offset by classifying a smaller proportion of participants as having the disease (fewer false positives) in 2 comparisons. There were no comparisons where the CPR missed a smaller proportion of diagnoses than clinical judgment and classified more participants as not having the disease. The design of the included studies allows evaluation of CPRs when their results are applied independently of clinical judgment. The performance of CPRs, when implemented by clinicians as a support to their judgment may be different.

Conclusions

In the limited studies to date, CPRs are rarely superior to clinical judgment and there is generally a trade-off between the proportion classified as not having disease and the proportion of missed diagnoses. Differences between the two methods of judgment are likely the result of different diagnostic thresholds for positivity. Which is the preferred judgment method for a particular clinical condition depends on the relative benefits and harms of true positive and false positive diagnoses.

Optimizing diagnostic imaging in the emergency department

While emergency diagnostic imaging use has increased significantly, there is a lack of evidence for corresponding improvements in patient outcomes. Optimizing emergency department (ED) diagnostic imaging has the potential to improve the quality, safety, and outcomes of ED patients, but to date, there have not been any coordinated efforts to further our evidence-based knowledge in this area. The objective of this article is to discuss six aspects of diagnostic imaging to provide background information on the underlying framework for the 2015 Academic Emergency Medicine consensus conference, "Diagnostic Imaging in the Emergency Department: A Research Agenda to Optimize Utilization." The consensus conference aims to generate a high priority research agenda for emergency diagnostic imaging that will inform the design of future investigations. The six components herein will serve as the group topics for the conference: 1) patient-centered outcomes research; 2) clinical decision rules; 3) training, education, and competency; 4) knowledge translation and barriers to image optimization; 5) use of administrative data; and 6) comparative effectiveness research: alternatives to traditional CT use.

Impact of d-Dimers on the Differential Diagnosis of Acute Chest Pain: Current Aspects Besides the Widely Known

d-dimers are cleavage products of fibrin that occur during plasmin-mediated fibrinolysis of blood clots. In the emergency department, d-dimer measurement represents a valuable and cost-effective tool in the differential diagnosis of acute chest pain including the main life-threatening entities: acute coronary syndrome, pulmonary embolism, and acute aortic syndrome. Whereas the diagnostic and prognostic values of d-dimer testing in acute coronary syndrome is of less priority, increases of d-dimers are frequently found in venous thromboembolism and acute aortic syndromes, especially acute aortic dissection. As to the high negative predictive value of d-dimer in those disorders, patients with low to intermediate pretest probability may profit in terms of less necessity of further non-invasive or even invasive imaging, simultaneously reducing potential complications and healthcare-related costs. However, because of the low specificity of the different d-dimer tests in contrast to its frequent usage, adequate interpretation is required. Age-related adjustment of d-dimer levels may be used to increase its diagnostic power.

Magnitude of D-dimer matters for diagnosing pulmonary embolus

OBJECTIVE

The objective of this study is to determine whether the magnitude of the D-dimer correlates with a higher likelihood of pulmonary embolus (PE).

METHODS

We performed an electronic chart review at our academic, tertiary care center, annual emergency department (ED) census greater than 100000. All patients with a chest computed tomographic (CT) scan with intravenous contrast and an elevated D-dimer level obtained in the ED between January 2001 and July 2008 were identified. Specific, predetermined, predefined data elements including sex, age, D-dimer level, and final ED diagnosis were recorded by a hypothesis-blinded extractor using a preformatted data form. D-dimer level less than 0.58 μg/mL constitutes the normal laboratory reference range for our turbidometric D-dimer assay. Data were analyzed using standard statistical methods, and a linear regression analysis was performed for correlation analysis of D-dimer and diagnosis of PE.

RESULTS

We identified 544 subjects who had both a chest CT scan performed and an elevated D-dimer level obtained in the ED. Fifty-eight subjects (10.7%; mean D-dimer, 4.9 μg/mL) were diagnosed with PE, and 486 (89.3%; mean D-dimer, 2.0) did not have a PE. The percentages of PE diagnoses for D-dimers in the ranges 0.58 to 1.0, 1.0 to 2.0, 2.0 to 5.0, 5.0 to 20.0, and greater than 20.0 (n = 11) were 3.6%, 8.0%, 16.2%, 35.3%, and 45.5%, respectively. The positive predictive value of PE for D-dimer level cutoffs of greater than 0.58, greater than 1.0, greater than 2.0, greater than 5.0, and greater than 20.0 was 10.7%, 14.6%, 22.2%, 37.8%, and 45.5%, respectively. Increasing D-dimer values were strongly correlated with the presence of PE (odds ratio, 1.1685 per stratum; P < .001).

CONCLUSION

Increasing magnitude of D-dimer correlates with increasing likelihood of PE diagnosed by CT angiography.

Overuse of computed tomography pulmonary angiography in the evaluation of patients with suspected pulmonary embolism in the emergency department

BACKGROUND

Clinical decision rules have been developed and validated for the evaluation of patients presenting with suspected pulmonary embolism (PE) to the emergency department (ED).

OBJECTIVES

The objective was to assess the percentage of computed tomographic pulmonary angiography (CT-PA) procedures that could have been avoided by use of the Wells score coupled with D-dimer testing (Wells/D-dimer) or pulmonary embolism rule-out criteria (PERC) in ED patients with suspected PE.

METHODS

The authors conducted a prospective cohort study of adult ED patients undergoing CT-PA for suspected PE. Wells score and PERC were calculated. A research blood sample was obtained for D-dimer testing for subjects who did not undergo testing as part of their ED evaluation. The primary outcome was PE by CT-PA or 90-day follow-up. Secondary outcomes were ED length of stay (LOS) and CT-PA time as defined by time from order to initial radiologist interpretation.

RESULTS

Of 152 suspected PE subjects available for analysis (mean ± SD age = 46.3 ± 15.6 years, 74% female, 59% black or African American, 11.8% diagnosed with PE), 14 (9.2%) met PERC, none of whom were diagnosed with PE. A low-risk Wells score (≤4) was assigned to 110 (72%) subjects, of whom only 38 (35%) underwent clinical D-dimer testing (elevated in 33/38). Of the 72 subjects with low-risk Wells scores who did not have D-dimers performed in the ED, archived research samples were negative in 16 (22%). All 21 subjects with low-risk Wells scores and negative D-dimers were PE-negative. CT-PA time (median = 160 minutes) accounted for more than half of total ED LOS (median = 295 minutes).

CONCLUSIONS

In total, 9.2 and 13.8% of CT-PA procedures could have been avoided by use of PERC and Wells/D-dimer, respectively.

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.

D-dimer threshold increase with pretest probability unlikely for pulmonary embolism to decrease unnecessary computerized tomographic pulmonary angiography

BACKGROUND

Increasing the threshold to define a positive D-dimer could reduce unnecessary computed tomographic pulmonary angiography (CTPA) for a suspected pulmonary embolism (PE) but might increase rates of a missed PE and missed pneumonia, the most common non-thromboembolic diagnosis seen on CTPA.

OBJECTIVE

Measure the effect of doubling the standard D-dimer threshold for 'PE unlikely' Revised Geneva (RGS) or Wells' scores on the exclusion rate, frequency and size of a missed PE and missed pneumonia.

METHODS

Patients evaluated for a suspected PE with 64-channel CTPA were prospectively enrolled from emergency departments (EDs) and inpatient units of four hospitals. Pretest probability data were collected in real time and the D-dimer was measured in a central laboratory. Criterion standard was CPTA interpretation by two independent radiologists combined with clinical outcome at 30 days.

RESULTS

Of 678 patients enrolled, 126 (19%) were PE+ and 93 (14%) had pneumonia. Use of either Wells' ≤ 4 or RGS ≤ 6 produced similar results. For example, with RGS ≤ 6 and standard threshold (< 500 ng mL(-1)), D-dimer was negative in 110/678 (16%), and 4/110 were PE+ (posterior probability 3.8%) and 9/110 (8.2%) had pneumonia. With RGS ≤ 6 and a threshold < 1000 ng mL(-1) , D-dimer was negative in 208/678 (31%) and 11/208 (5.3%) were PE+, but 10/11 missed PEs were subsegmental and none had concomitant DVT. Pneumonia was found in 12/208 (5.4%) with RGS ≤ 6 and D-dimer < 1000 ng mL(-1).

CONCLUSIONS

Doubling the threshold for a positive D-dimer with a PE unlikely pretest probability could reduce CTPA scanning with a slightly increased risk of missed isolated subsegmental PE, and no increase in rate of missed pneumonia.

Critical issues in the evaluation and management of adult patients presenting to the emergency department with suspected pulmonary embolism

This clinical policy from the American College of Emergency Physicians is the revision of a 2003 clinical policy on the evaluation and management of adult patients presenting with suspected pulmonary embolism (PE).(1) A writing subcommittee reviewed the literature to derive evidence-based recommendations to help clinicians answer the following critical questions: (1) Do objective criteria provide improved risk stratification over gestalt clinical assessment in the evaluation of patients with possible PE? (2) What is the utility of the Pulmonary Embolism Rule-out Criteria (PERC) in the evaluation of patients with suspected PE? (3)What is the role of quantitative D-dimer testing in the exclusion of PE? (4) What is the role of computed tomography pulmonary angiogram of the chest as the sole diagnostic test in the exclusion of PE? (5) What is the role of venous imaging in the evaluation of patients with suspected PE? (6) What are the indications for thrombolytic therapy in patients with PE? Evidence was graded and recommendations were given based on the strength of the available data in the medical literature.

Cost-effectiveness of strategies for diagnosing pulmonary embolism among emergency department patients presenting with undifferentiated symptoms

STUDY OBJECTIVE

Symptoms associated with pulmonary embolism can be nonspecific and similar to many competing diagnoses, leading to excessive costly testing and treatment, as well as missed diagnoses. Objective studies are essential for diagnosis. This study evaluates the cost-effectiveness of different diagnostic strategies in an emergency department (ED) for patients presenting with undifferentiated symptoms suggestive of pulmonary embolism.

METHODS

Using a probabilistic decision model, we evaluated the incremental costs and effectiveness (quality-adjusted life-years gained) of 60 testing strategies for 5 patient pretest categories (distinguished by Wells score [high, moderate, or low] and whether deep venous thrombosis is clinically suspected). We performed deterministic and probabilistic sensitivity analyses.

RESULTS

In the base case, for all patient pretest categories, the most cost-effective diagnostic strategy is to use an initial enzyme-linked immunosorbent assay D-dimer test, followed by compression ultrasonography of the lower extremities if the D-dimer is above a specified cutoff. The level of the preferred cutoff varies with the Wells pretest category and whether a deep venous thrombosis is clinically suspected. D-dimer cutoffs higher than the current recommended cutoff were often preferred for patients with even moderate and high Wells categories. Compression ultrasonography accuracy had to decrease below commonly cited levels in the literature before it was not part of a preferred strategy.

CONCLUSION

When pulmonary embolism is suspected in the ED, use of an enzyme-linked immunosorbent assay D-dimer assay, often at cutoffs higher than those currently in use (for patients in whom deep venous thrombosis is not clinically suspected), followed by compression ultrasonography as appropriate, can reduce costs and improve outcomes.