Pretest risk assessment in suspected acute pulmonary embolism

Role of D-dimer Assays in the Diagnostic Evaluation of Pulmonary Embolism

The diagnosis of pulmonary embolism (PE) remains challenging despite the evolution of well-validated clinical algorithms over the past few decades, largely because of nonspecific clinical features altering clinician suspicion. D-dimer is a simple noninvasive test that is an essential part of the diagnostic algorithm but is often deemed to be of little value in patients who are elderly or have other comorbidities. We describe a case of an elderly man who presented with clinical features and initial imaging consistent with pneumonia and a positive D-dimer test. Adherence to the suggested diagnostic algorithm and obtaining chest imaging, however, prevented what could have been a catastrophic missed diagnosis of PE. We review existing evidence on the importance of suspecting PE in the presence of alternative diagnosis and explore the literature on the association between the magnitude of D-dimer and the diagnosis of PE.

Combination pretest probability assessment and D-dimer did not reduce outpatient imaging for venous thromboembolism in a tertiary care hospital emergency department

INTRODUCTION

Venous thromboembolism (VTE) is difficult to diagnose yet potentially life threatening. A low-risk pretest probability (PTP) assessment combined with a negative D-dimer can rule out VTE in two-thirds of outpatients, reducing the need for imaging. Real-life implementation of this strategy is associated with several challenges.

METHODS

We evaluated the impact of introducing a standardized diagnostic algorithm including a mandatory PTP assessment and D-dimer on radiologic test use for VTE in our emergency department (ED). A retrospective review of all ED visits for suspected VTE in the year prior to and following the introduction of this algorithm was conducted. VTE diagnosis was based on imaging. Guideline compliance was also assessed.

RESULTS

ED visits were investigated for suspected VTE in the pre- and postintervention periods (n  =  1,785). Most D-dimers (95%) ordered were associated with a PTP assessment, and 50% of visits assigned a low PTP had a negative D-dimer. The proportion of imaging tests ordered for VTE in all ED visits was unchanged postintervention (1.9% v. 2.0%). The proportion of patients with suspected VTE in whom VTE was confirmed on imaging decreased postintervention (10.2% v. 14.1%).

CONCLUSION

In spite of excellent compliance with our algorithm, we were unable to reduce imaging for VTE. This may be due to a lower threshold for suspecting VTE and an increase in investigation for VTE combined with a high false positive rate of our D-dimer assay in low-pretest probability patients. This study highlights two common real-life challenges with adopting this strategy for VTE investigation.

Current approach to the diagnosis of acute nonmassive pulmonary embolism

Pulmonary embolism is a common and potentially lethal disease. Given the variable presentation and associated morbidity of this condition, an accurate and efficient diagnostic algorithm is required. Clinical pretest probability serves as the root of any diagnostic approach. We, thus, review several clinical decision rules that may help standardize this determination. Using a review of the literature, the accuracy, predictive values, and likelihood ratios for several diagnostic tests are described. The combination of these tests, based on the pretest probability of disease, can be used in a Bayesian fashion to make accurate treatment decisions. A completely noninvasive diagnostic algorithm for patients presenting with suspected acute pulmonary embolism is proposed.

Diagnostic classification in patients with suspected deep venous thrombosis: physicians' judgement or a decision rule?

BACKGROUND

Clinical decision rules can aid in referral decisions for ultrasonography in patients suspected of having deep venous thrombosis (DVT), but physicians are not always convinced of their usefulness and rely on their own judgement.

AIM

To compare the performance of a clinical decision rule with the probability of DVT presence as estimated by GPs.

DESIGN OF STUDY

Cross-sectional survey.

SETTING

Primary care practices in The Netherlands.

METHOD

GPs (n = 300) estimated the probability of the presence of DVT (range 0-100%) and calculated the score for the clinical decision rule in 1028 consecutive patients with suspected DVT. The clinical decision rule uses a threshold of three points and so, for the GP estimates, thresholds were introduced at 10% and 20%. If scores were below these estimates, it was not considered necessary to refer patients for further examination. Differences between the clinical decision rule and the GP estimates were calculated; this is discrimination (c-statistic) and classification of patients.

RESULTS

Data of 1002 patients were eligible for analysis. DVT was observed in 136 (14%) patients. Both the clinical decision rule and GP estimates had good discriminative power (c-statistic of 0.80 and 0.82 respectively). Fewer patients were referred when using the clinical decision rule compared with a referral decision based on GP estimates: 51% versus 79% and 65% (thresholds at 10% and 20% respectively). Both strategies missed a similar and low proportion of patients who did have DVT (range 1.4-2.0%).

CONCLUSION

In patients suspected of DVT both GP estimates and a clinical decision rule can safely discriminate in patients with and without DVT. However, fewer patients are referred for ultrasonography when GPs rely on a clinical decision rule to guide their decision making.

Underutilization of evidence-based strategies in the diagnosis and treatment of venous thromboembolism among trainees

BACKGROUND

The knowledge and attitude of trainees toward the use of prediction rules in the diagnosis of venous thromboembolism (VTE) is understudied. The extent of knowledge as far as imaging strategies in the setting of VTE and use of low molecular weight heparin (LMWH) among trainees is also understudied.

METHODS

This was a cross-sectional study; between October, 2006 and March, 2008, surveys were distributed at grand rounds and national medicine board review courses. Respondents returning completed surveys included 43 medicine attendings, 139 residents, and 134 medical students Emergency physicians were called at work and 46 completed an abbreviated version of the survey. Attending and trainee responses were compared.

RESULTS

Over 60% of students and 40% of residents did not use any prediction rules. Most attendings (>60%) did not use a prediction rule. Among attendings, 48% of emergency physicians and 30% of medicine attendings felt that prediction rules were too complex to use. Knowledge about imaging techniques and diagnostic protocols for VTE were worse for students than for residents. A substantial minority of all respondents (17% of students, 12% of residents and 13% of medicine attendings) would not use LMWH in the therapy of non-massive pulmonary embolism. In general, level of training did not translate into a greater proportion of correct responses to clinical scenarios or greater knowledge about imaging systems and strategies.

CONCLUSION

Trainees do not use a structured approach to VTE diagnosis. LMWH therapy is underutilized by a large minority of trainees and attendings. A top-down approach is needed to revitalize evidence-based management of VTE.