Outpatient diagnosis of pulmonary embolism: the MIOPED (Manchester Investigation Of Pulmonary Embolism Diagnosis) study

BTS guidelines for the initial outpatient management of pulmonary embolism: there’s no place like home

This article provides an overview of the highlights and key points of the new BTS guideline for the initial outpatient management of pulmonary embolism.

Study of compliance with a clinical pathway for suspected pulmonary embolism

BACKGROUND/AIMS

Clinical pathways to guide the investigation of suspected pulmonary embolism have been increasingly adopted by emergency departments worldwide. This study evaluated the compliance with a clinical pathway that combines risk assessment (Wells score) with d-dimer, ventilation-perfusion scanning or computed tomographic pulmonary angiography (CTPA). The aims of this study were to identify factors that contribute to compliance and to assess patient outcomes and resource utilization.

METHODS

Repeated retrospective chart reviews of 239 patients who underwent investigation for pulmonary embolism through our emergency department extracted patient demographics, pathway parameters and patient outcomes. A phone interview at 3-month follow up was carried out.

RESULTS

Incidence of pulmonary embolism was 8.4% (n= 20). Compliance to the clinical pathway occurred in 120 subjects (50.2%). Non-compliance occurred in 71 subjects (29.7%). Forty-eight subjects (20.1%) underwent risk assessments, but subsequent diagnostic tests did not conform to the stated pathway (partial compliance). Compliance was poor in subjects assessed by non-emergency department doctors (χ(2) = 27.95, P≤ 0.001). Compliance occurred less in pregnant subjects (χ(2) = 7.27, P= 0.007) and those with chronic respiratory disease (χ(2) = 5.31, P= 0.021). Subjects in the compliant group were less likely to undergo CTPA (odds ratio 2.07 (1.16-3.70), P= 0.012).

CONCLUSIONS

Compliance with this clinical pathway allowed emergency department doctors in an Australian university teaching hospital to complete diagnostic testing for suspected pulmonary embolism appropriately unless non-emergency department doctors became involved. Compliance with this pathway altered the distribution of diagnostic tests performed with less reliance on CTPA, but was not associated with better patient outcomes.

Outpatient imaging for pulmonary embolism may only be suitable for a minority

In this study we model the impact of introducing outpatient investigation of pulmonary thrombo-embolism (PTE) to the acute medical unit (AMU) using the Pulmonary Embolism Severity Index (PESI) decision rule. Specifically, we ask what proportion of patients requiring imaging could be investigated without admission, and how many bed-days this would save.  We obtained records for all medical patients who had imaging for PTE in a six-month period at a large teaching hospital with a 40-bedded AMU. The patients were categorized into suitability for outpatient investigation using a combination of the PESI rule and practical considerations. Three hundred and fifty-nine separate presentations were identified. From available records, 31 patients (9.2%, 95% confidence interval [CI] 6.6-12.8%) had no contraindications to outpatient management. These patients used a total of 79 bed-days in the six-month period, or 1.1% (95% CI 0.8-1.5%) of the maximum AMU bed occupancy. Around 10% of patients who require imaging for suspected PTE could be triaged to outpatient investigation using the PESI tool. Adopting this method to triage patients of ambulatory care, would have only a modest effect on acute medical bed occupancy, but remains a valid option for motivated patients in the low-risk category.

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.

Accuracy of very low pretest probability estimates for pulmonary embolism using the method of attribute matching compared with the Wells score

OBJECTIVES

Attribute matching matches an explicit clinical profile of a patient to a reference database to estimate the numeric value for the pretest probability of an acute disease. The authors tested the accuracy of this method for forecasting a very low probability of venous thromboembolism (VTE) in symptomatic emergency department (ED) patients.

METHODS

The authors performed a secondary analysis of five data sets from 15 hospitals in three countries. All patients had data collected at the time of clinical evaluation for suspected pulmonary embolism (PE). The criterion standard to exclude VTE required no evidence of PE or deep venous thrombosis (DVT) within 45 days of enrollment. To estimate pretest probabilities, a computer program selected, from a large reference database of patients previously evaluated for PE, patients who matched 10 predictor variables recorded for each current test patient. The authors compared the outcome frequency of having VTE [VTE(+)] in patients with a pretest probability estimate of <2.5% by attribute matching, compared with a value of 0 from the Wells score.

RESULTS

The five data sets included 10,734 patients, and 747 (7.0%, 95% confidence interval [CI] = 6.5% to 7.5%) were VTE(+) within 45 days. The pretest probability estimate for PE was <2.5% in 2,975 of 10,734 (27.7%) patients, and within this subset, the observed frequency of VTE(+) was 48 of 2,975 (1.6%, 95% CI = 1.2% to 2.1%). The lowest possible Wells score (0) was observed in 3,412 (31.7%) patients, and within this subset, the observed frequency of VTE(+) was 79 of 3,412 (2.3%, 95% CI = 1.8% to 2.9%) patients.

CONCLUSIONS

Attribute matching categorizes over one-quarter of patients tested for PE as having a pretest probability of <2.5%, and the observed rate of VTE within 45 days in this subset was <2.5%.

Diagnostic accuracy of the Triage® D-dimer test for exclusion of venous thromboembolism in outpatients

BACKGROUND

We evaluated the diagnostic performance of the Triage D-dimer test, a new fast quantitative point-of-care whole blood D-dimer assay and compared it with the Vidas D-dimer assay.

MATERIALS AND METHODS

The study population comprised 319 outpatients for whom D-dimer testing was requested in order to rule out venous thromboembolism (VTE). Routine testing consisted of a plasma ELISA D-dimer analysis (Vidas). For all included patients, an additional EDTA whole blood D-dimer test (Triage) was performed. Patients were classified by reference imaging or by follow-up of the medical record. Accuracy indices, receiver operating characteristics and the kappa coefficient for agreement were calculated using the cutoff values recommended by the manufacturer.

RESULTS

Prevalence of VTE was 14%. Sensitivity and specificity for VTE were 98% (95%CI: 88-100) and 34% (95%CI: 28-40) for Vidas and 91% (95%CI: 78-97) and 42% (95%CI: 36-48) for Triage, respectively. The differences in sensitivity and specificity between both D-dimer assays were statistically significant (McNemar, p<0.0001). ROC-curve analysis yielded an area under the curve of 0.83 (95%CI: 0.76-0.89) for the Vidas and 0.81 (95%CI: 0.74-0.88) for the Triage (p=0.396). The kappa coefficient for agreement between Vidas and Triage was 0.75 (95%CI: 0.68-0.79).

CONCLUSIONS

The Triage and Vidas D-dimer tests show comparable diagnostic accuracy. Vidas showed a significant higher sensitivity. Our findings strongly suggest lowering the cutoff for the Triage D-dimer test from 400 to 350 ng/mL. In this way specificity lowers from 42 to 38%, but, more importantly, sensitivity increases from 91 to 95%.