The yield of CT pulmonary angiograms to exclude acute pulmonary embolism

Diagnostic Yield, Radiation Exposure, and the Role of Clinical Decision Rules to Limit Computed Tomographic Pulmonary Angiography-Associated Complications

OBJECTIVES

Computed tomographic pulmonary angiography (CT-PA) is associated with significant cost, contrast, and radiation exposure. Clinical decision rules (CDRs) reduce the need for diagnostic imaging; however, their utility in the medical intensive care unit (MICU) remains unknown. We explored the diagnostic yield and complications associated with CT-PA (radiation exposure and contrast-induced acute kidney injury [AKI]) while investigating the efficacy of CDRs to reduce unnecessary testing.

METHODS

All CT-PAs performed in an academic MICU for 4 years were retrospectively reviewed. The Wells and revised Geneva scores (CDRs) and radiation dose per CT-PA were calculated, and the incidence of post-CT-PA AKI was recorded.

RESULTS

A total of 439 studies were analyzed; the diagnostic yield was 11% (48 PEs). Positive CT-PAs were associated with a higher Wells score (5.8 versus 3.2, P < 0.001), but similar revised Geneva scores (6.4 versus 6.0, P = 0.32). A Wells score of ≥4 had a positive likelihood ratio of 2.1 with a negative predictive value of 98.2. More than half (88.9%) of patients with a Wells score of ≤4 developed an AKI, with 55.6% of those having recovery of renal function.

CONCLUSIONS

There is overutilization of CT-PA in the MICU. The Wells score retains its negative predictive value in critically ill adult patients and may aid to limit radiation exposure and contrast-induced AKI in MICU.

Clinical predictors of pulmonary embolism for inpatients: are computed tomography pulmonary angiograms being requested appropriately?

BACKGROUND

The heterogeneity of inpatient pulmonary embolism (PE) presentations may lead to computed tomography pulmonary angiograms (CTPA) being over-requested. Current clinical predictors for PE, including Wells criteria and Pulmonary Embolism Rule-out Criteria (PERC), have predominantly focussed on outpatient and emergency department populations.

AIM

To determine the clinical indicators for ordering inpatient CTPA and the predictors of positive scans for PE.

METHODS

Consecutive inpatient CTPA (performed >24 h after admission) from January 2017 to December 2017 were retrospectively reviewed. Variables including baseline characteristics, vital signs and risk factors for PE were extracted.

RESULTS

A total of 312 CTPA was reviewed (average patient age 67 years; 46% male) and 36 CTPA were positive for PE (11.5%). The average time to inpatient CTPA request was 7 days. Clinical indicators associated with positive scans were hypoxia (odds ratio (OR) 2.4; 95% confidence interval (CI) 1.1-5.6), tachypnoea (OR 2.5; 95% CI 1.2-6.0), recent surgery or immobilisation (OR 2.7; 95% CI 1.2-6.4), S1Q3T3 pattern on electrocardiogram (ECG; OR 7.2; 95% CI 1.4-35.7) and right bundle branch block pattern on ECG (OR 4.7; 95% CI 1.6-13.1). Hypotension, fever and malignancy were not significant. Both PERC and Wells criteria had poor positive predictive value (12% and 27% respectively), but the negative predictive value for PERC and Wells was 100% and 95.8% respectively.

CONCLUSION

Inpatient CTPA appear to be over-requested and can potentially be rationalised based on a combination of clinical predictors and Wells criteria and/or PERC rule. Further prospective studies are needed to develop accurate clinical decision tools targeted towards inpatients.

The Utilisation of Computed Tomography Pulmonary Angiography in a Regional Victorian Emergency Department

BACKGROUND

Pulmonary embolism (PE) is a critical condition with various recognized risk factors. This study investigates these factors in a regional Australian population.

AIMS

The primary aim is to examine the significance of traditional risk factors in the clinical decision to request a computed tomography pulmonary angiography (CTPA) scan for suspected PE within this population and assess the association between the timing of CTPA requests (office vs. after-hours) and PE occurrence.

METHODS

In this single-center retrospective study, we analyzed data from 434 patients undergoing CTPA at Goulburn Valley Health's (GVH) emergency department (ED) between January and August 2022. Covariates included age, clinical indications, and medical background. Statistical tests were applied with a p-value <0.05 indicating significance.

RESULTS

Pulmonary embolism was diagnosed in 39 (20.9%) males and 17 (6.9%) females, with a mean age of 65.04 years (SD: 16.11). Univariate regression indicated a positive association between age and PE. Multivariate analysis showed a significant positive association for unilateral lower limb (LL) swelling/deep vein thrombosis (DVT) (OR: 5.474, p=0.003) and a significant negative association for being female (OR: 0.308, p<0.001). Variables such as shortness of breath, tachycardia, syncope, and chest pain were not significantly associated with PE. No association was found between CTPA request time and PE (χ²=0.9535, df=1, p=0.3288).

CONCLUSION

Increasing age and unilateral LL swelling/DVT are significantly associated with PE. Some signs and symptoms showed negative or positive odds but were not statistically significant. The timing of CTPA requests did not correlate with PE incidence.

Implementation of the YEARS algorithm to optimise pulmonary embolism diagnostic workup in the emergency department

BACKGROUND

Excessive use of CT pulmonary angiography (CTPA) to investigate pulmonary embolism (PE) in the emergency department (ED) contributes to adverse patient outcomes. Non-invasive D-dimer testing, in the context of a clinical algorithm, may help decrease unnecessary imaging but this has not been widely implemented in Canadian EDs.

AIM

To improve the diagnostic yield of CTPA for PE by 5% (absolute) within 12 months of implementing the YEARS algorithm.

MEASURES AND DESIGN

Single centre study of all ED patients >18 years investigated for PE with D-dimer and/or CTPA between February 2021 and January 2022. Primary and secondary outcomes were the diagnostic yield of CTPA and frequency of CTPA ordered compared with baseline. Process measures included the percentage of D-dimer tests ordered with CTPA and CTPAs ordered with D-dimers <500 µg/L Fibrinogen Equivalent Units (FEU). The balancing measure was the number of PEs identified on CTPA within 30 days of index visit. Multidisciplinary stakeholders developed plan- do-study-act cycles based on the YEARS algorithm.

RESULTS

Over 12 months, 2695 patients were investigated for PE, of which 942 had a CTPA. Compared with baseline, the CTPA yield increased by 2.9% (12.6% vs 15.5%, 95% CI -0.06% to 5.9%) and the proportion of patients that underwent CTPA decreased by 11.4% (46.4% vs 35%, 95% CI -14.1% to -8.8%). The percentage of CTPAs ordered with a D-dimer increased by 26.3% (30.7% vs 57%, 95% CI 22.2% 30.3%) and there were two missed PE (2/2695, 0.07%).

IMPACT

Implementing the YEARS criteria may safely improve the diagnostic yield of CTPAs and reduce the number of CTPAs completed without an associated increase in missed clinically significant PEs. This project provides a model for optimising the use of CTPA in the ED.

CTPA ordering trends in local emergency departments: are they increasing and did they increase as a result of COVID-19?

PURPOSE

Ordering trends for computed tomographic pulmonary angiogram (CTPA) studies by local emergency departments were assessed, along with the impact of the COVID-19 pandemic on these ordering trends and CTPA positivity rates.

METHODS

A retrospective quantitative analysis was performed on all CTPA studies ordered between February 2018 - January 2022 by three local tertiary care emergency rooms to investigate for pulmonary embolism. Data collected from the first two years of the COVID-19 pandemic was compared to the two years prior to the pandemic to assess for significant changes in ordering trends and positivity rates.

RESULTS

The overall number of CTPA studies ordered increased from 534 studies in 2018-2019 to 657 in 2021-2022 and the rate of positive diagnosis of acute pulmonary embolism varied between 15.8% to 19.5% over the four years studied. There was no statistically significant difference in the number of CTPA studies ordered when comparing the first two years of the COVID-19 pandemic to the two years immediately prior; however, the positivity rate was significantly higher during the first two years of the pandemic.

CONCLUSION

Over the studied period from 2018-2022, the overall number of CTPA studies ordered by local emergency departments has increased, in line with literature reports from other locations. There was also a correlation between the onset of the COVID-19 pandemic and CTPA positivity rates, possibly secondary to the prothrombotic nature of this infection or the increase in sedentary lifestyles during lockdown periods.

The impact of performance feedback reports on physician ordering behavior in the use of computed tomography pulmonary angiography (CTPA)

PURPOSE

The increased utilization, and potential overutilization, of computed tomography pulmonary angiography (CTPA) is a well-recognized issue within emergency departments (EDs). The objective of this study is to determine the impact of performance feedback reports on CTPA ordering behavior among ED physicians.

METHODS

We conducted a prospective study of the impact of individualized performance feedback reports on the ordering behavior of physicians working at two high-volume community EDs in Ontario, Canada. We generated individualized reports (or "Dashboards") for each ED physician containing detailed feedback and peer comparison for each physician's CTPA ordering. Our baseline pre-intervention period was January 1 to December 31, 2018, and our intervention period was January 1, 2019, to December 31, 2021. We tracked individual and group ordering behavior through the study period. Our primary outcomes are impact of feedback on (1) overall group ordering rate and (2) overall diagnostic yield. Secondary analysis was done to determine the impact of the intervention on those physicians with the highest CTPA utilization rate.

RESULTS

There was no statistically significant difference in the diagnostic yield of the included physicians in either of the years of the intervention period. There was a statically significant increase in the utilization rate for CTPA from 2018 to 2020 and 2021 from 5.9 to 7.9 and 11.4 CTPAs per 1000 ED visits respectively (p < 0.5).

CONCLUSION

Our study found no consistent significant impact of individualized feedback and peer comparison on physician ordering of CTPAs. This points to a potentially greater impact of environmental and institutional factors, as opposed to physician-targeted quality improvement measures, on physician ordering behavior.

Comparison of Efficacy and Safety between Thrombolysis Plus Anticoagulation vs. Anticoagulation Alone for the Treatment of Acute Submassive Pulmonary Embolism: A Systematic Review and Meta-analysis

OBJECTIVE

The objective of this study is to compare the efficacy and safety of thrombolysis plus anticoagulant therapy vs. anticoagulant therapy alone in acute submassive pulmonary embolism (PE).

MATERIALS AND METHODS

The PubMed, Embase, and Cochrane Library databases were searched for randomized clinical trials comparing thrombolytic therapy and anticoagulation vs. anticoagulation alone in acute submassive PE patients from 1 Jan 1980 to 20 Jan 2021, with no drug or dose restrictions. Data on upgraded treatment of clinical deterioration, all-cause mortality, PE recurrence and bleeding events were extracted and analyzed using Revman 5.3 software.

RESULTS

A total of 10 randomized controlled trials involving 1871 patients were included in the study after screening. In terms of efficacy, thrombolysis combined with anticoagulant therapy reduced the need for upgrading treatment (3.6 vs. 10.9%, risk ratio (RR) 0.36, 95% confidence interval (CI) 0.24- 0.54, p<0.00001) and PE recurrence (0.8 vs. 2.9%, RR 0.33, 95% CI 0.16-0.69, p=0.003) in patients with acute submassive PE. Compared with anticoagulant therapy alone, the concomitant use of thrombolysis was associated with lower all-cause mortality (1.3 vs. 3.0%, RR 0.47, 95% CI 0.26-0.87, p=0.02), but it increased minor bleeding rate (31.4 vs. 8.4%, RR 3.71, 95% CI 2.82-4.88, p<0.0001) and major bleeding rate (8.8 vs. 2.6%, RR 3.35, 95%CI 2.03-5.54, p<0.0001).

CONCLUSION

The use of thrombolysis plus anticoagulant therapy in acute submassive PE was negatively associated with patients requiring escalation of treatment, PE recurrence, and all-cause mortality, but it was positively associated with bleeding.

Risk stratification of emergency department patients with acute pulmonary thromboembolism: Is chest pain a reason to investigate?

BACKGROUND

This study aimed to risk-stratify chest pain as a presenting symptom in patients with a diagnosis of pulmonary thromboembolism (PE) to assess for any association. In addition, this study aimed to assess traditionally acknowledged PE risk factors in an Australian population.

METHODS

This was a retrospective single-centre cohort study assessing patients who presented to our emergency department during the period of 1 January 2019 to 1 January 2020. 730 consecutive patients who went on to computed tomography pulmonary angiography (CTPA) examination after presentation were included.

RESULTS

The rate of CTPA being positive in this study was 11.6% (85/730). Chest pain was associated with a non-significant reduction in the odds of PE (OR 0.774, P = 0.327). Univariate analysis showed significantly increased odds of a diagnosis of PE with presentation for leg pain/swelling (OR 6.670, P < 0.001). Multivariate analysis showed increasing age (OR 1.018, 95% CI 1.002-1.034, P = 0.024), clinical signs of a DVT (OR 3.194, 95% CI 1.803-5.657, P < 0.001) and positive D-dimer (OR 1.762, 95% CI 1.011-3.071, P = 0.046) were associated with increased odds of PE.

CONCLUSION

In this study, Emergency Department presentation with chest pain, whilst the most common reason to perform a CTPA, resulted in reduced odds with regard to the diagnosis of pulmonary thromboembolism. The use of CTPA in this setting may be rationalised according to other factors such as localised leg pain as a symptom, signs of DVT, increasing age or positive D-dimer.

Canadian Society of Thoracic Radiology/Canadian Association of Radiologists Best Practice Guidance for Investigation of Acute Pulmonary Embolism, Part 1: Acquisition and Safety Considerations

Acute pulmonary embolism (APE) is a well-recognized cause of circulatory system compromise and even demise which can frequently present a diagnostic challenge for the physician. The diagnostic challenge is primarily due to the frequency of indeterminate presentations as well as several other conditions which can have a similar clinical presentation. This often obliges the physician to establish a firm diagnosis due to the potentially serious outcomes related to this disease. Computed tomography pulmonary angiography (CTPA) has increasingly cemented its role as the primary investigation tool in this clinical context and is widely accepted as the standard of care due to several desired attributes which include great accuracy, accessibility, rapid turn-around time and the ability to suggest an alternate diagnosis when APE is not the culprit. In Part 1 of this guidance document, a series of up-to-date recommendations are provided to the reader pertaining to CTPA protocol optimization (including scan range, radiation and intravenous contrast dose), safety measures including the departure from breast and gonadal shielding, population-specific scenarios (pregnancy and early post-partum) and consideration of alternate diagnostic techniques when clinically deemed appropriate.

Utilization of serum D-dimer assays prior to computed tomography pulmonary angiography scans in the diagnosis of pulmonary embolism among emergency department physicians: a retrospective observational study

Background

A variety of evidence-based algorithms and decision rules using D-Dimer testing have been proposed as instruments to allow physicians to safely rule out a pulmonary embolism (PE) in low-risk patients.

Objective

To describe the prevalence of D-Dimer utilization among emergency department (ED) physicians and its impact on positive yields and utilization rates of Computed Tomography Pulmonary Angiography (CTPA).

Methods

Data was collected on all CTPA studies ordered by ED physicians at three sites during a 2-year period. Using a chi-square test, we compared the diagnostic yield for those patients who had a D-Dimer prior to their CTPA and those who did not. Secondary analysis was done to examine the impact of D-Dimer testing prior to CTPA on individual physician diagnostic yield or utilization rate.

Results

A total of 2811 CTPAs were included in the analysis. Of these, 964 CTPAs (34.3%) were ordered without a D-Dimer, and 343 (18.7%) underwent a CTPA despite a negative D-Dimer. Those CTPAs preceded by a D-Dimer showed no significant difference in positive yields when compared to those ordered without a D-Dimer (9.9% versus 11.3%, p = 0.26). At the individual physician level, no statistically significant relationship was found between D-Dimer utilization and CTPA utilization rate or diagnostic yield.

Conclusion

This study provides evidence of suboptimal adherence to guidelines in terms of D-Dimer screening prior to CTPA, and forgoing CTPAs in patients with negative D-Dimers. However, the lack of a positive impact of D-Dimer testing on either CTPA diagnostic yield or utilization rate is indicative of issues relating to the high false-positive rates associated with D-Dimer screening.

Diagnostic yield of computed tomographic pulmonary angiography for suspected pulmonary embolism varies across settings within a community-based health system

PURPOSE

The diagnostic yield of computed tomographic pulmonary angiography (CTPA) for pulmonary embolism varies in the literature, and very little data is available regarding community-based systems. This study evaluates the yield of CTPA for pulmonary embolism across a variety of patient care settings in a community-based healthcare system, providing relevant benchmarks for potential quality improvement efforts.

METHODS

This retrospective study included data collected from three sites within a single community-based healthcare system, including a tertiary care level 1 trauma center, an urban community hospital, and a suburban free-standing emergency department. CTPAs were identified by Current Procedural Terminology codes, and diagnoses of pulmonary embolism were identified via International Classification of Diseases codes. A total of 7850 CTPA studies met criteria for inclusion between January 1, 2012, and October 8, 2014.

RESULTS

Pulmonary embolism was found in 884 (11.3%) of the studies performed. Outpatients had a lower yield of pulmonary embolism (3.8%, p < 0.001) compared with inpatients (14.1%) and emergency department patients (10.7%, p < 0.001). Patients with diagnoses of deep vein thrombosis or neoplasm had increased incidence of pulmonary embolism when compared with patients without these diagnoses (p < 0.001 for both).

CONCLUSION

The overall yield of CTPA for pulmonary embolism in this community-based system was similar to that at academic centers. The yield was significantly lower in the outpatient setting compared with studies originating in the emergency department or inpatient setting.

Pulmonary embolism in hospitalised patients with COVID-19

BACKGROUND

Coronavirus disease 2019 (COVID-19) is characterised by dyspnoea and abnormal coagulation parameters, including raised D-dimer. Data suggests a high incidence of pulmonary embolism (PE) in ventilated patients with COVID-19.

OBJECTIVES

To determine the incidence of PE in hospitalised patients with COVID-19 and the diagnostic yield of Computer Tomography Pulmonary Angiography (CTPA) for PE. We also examined the utility of D-dimer and conventional pre-test probability for diagnosis of PE in COVID-19.

PATIENTS/METHODS

Retrospective review of single-centre data of all CTPA studies in patients with suspected or confirmed COVID-19 identified from Electronic Patient Records (EPR).

RESULTS

There were 1477 patients admitted with COVID-19 and 214 CTPA scans performed, of which n = 180 (84%) were requested outside of critical care. The diagnostic yield for PE was 37%. The overall proportion of PE in patients with COVID-19 was 5.4%. The proportions with Wells score of ≥4 ('PE likely') was 33/134 (25%) without PE vs 20/80 (25%) with PE (P = 0.951). The median National Early Warning-2 (NEWS2) score (illness severity) was 5 (interquartile range [IQR] 3-9) in PE group vs 4 (IQR 2-7) in those without PE (P = 0.133). D-dimer was higher in PE (median 8000 ng/mL; IQR 4665-8000 ng/mL) than non-PE (2060 ng/mL, IQR 1210-4410 ng/mL, P < 0.001). In the 'low probability' group, D-dimer was higher (P < 0.001) in those with PE but had a limited role in excluding PE.

CONCLUSIONS

Even outside of the critical care environment, PE in hospitalised patients with COVID-19 is common. Of note, approaching half of PE events were diagnosed on hospital admission. More data are needed to identify an optimal diagnostic pathway in patients with COVID-19. Randomised controlled trials of intensified thromboprophylaxis are urgently needed.

Weight-Adjusted Contrast Administration in the Computed Tomography Evaluation of Pulmonary Embolism

INTRODUCTION

Computed tomography pulmonary angiogram (CTPA) is widely considered the gold standard for diagnosis of pulmonary embolism (PE) with previous studies demonstrating high sensitivity and specificity. Despite this, nondiagnostic and indeterminate CTPA rates of 5%-26% remain a concern. As part of a continuing quality assurance program, a new weight-adjusted contrast dose and increased administration rate CTPA protocol was studied with an aim to improve diagnostic accuracy of PE evaluation.

METHODS

A total of 2,398 CTPA examinations were reviewed to assess pulmonary arterial enhancement and PE yield in this retrospective study. Between 1 August 2014 and 1 August 2015, 1,133 patients received a fixed-volume (60 mL) contrast dose technique at 4 mL/s (protocol A). A new protocol was then implemented as part of a continuing quality assurance program. Between 15 September 2015 and 15 September 2016, 1,265 patients received a weight-adjusted contrast dose (1 mL/kg) and increased administration rate (5 mL/s) CTPA technique (protocol B). Studies were classed into categories based on quality of study; diagnostic: HU > 211, nondiagnostic: HU < 211 and PE yield; positive, negative, and indeterminate. These variables were compared with cross-sectional surface area to assess the relationship between patient habitus, CTPA diagnostic quality, and PE yield.

RESULTS

A weight-adjusted contrast dose and increased administration rate CTPA protocol (protocol B) resulted in a significant increase in mean PA enhancement (P < .0001), 55.23% decrease in nondiagnostic studies and 43.04% decrease in indeterminate studies. Protocol B demonstrated increased positive and negative CTPA rates with decreased indeterminate rates from 12.38% to 7.04%. Comparison with cross-sectional area demonstrated significant increase in proportion of diagnostic studies and reduction in nondiagnostic and indeterminate CTPAs using protocol B in obese patients.

CONCLUSIONS

A weight-adjusted contrast dose and increased administration rate CTPA protocol can significantly increase PA enhancement, especially in obese patients, resulting in greater high-quality and fewer nondiagnostic and indeterminate CTPA examinations. A CTPA protocol with a higher rate of conclusive examinations can provide greater confidence in PE evaluation for reporting radiologists and accurate clinical decision-making pathways for referring physicians.

Pulmonary embolism rule out: positivity and factors affecting the yield of CT angiography

OBJECTIVE

CT pulmonary angiography (CTPA) is one of the most commonly ordered CT imaging tests. It is often believed to be overutilised with few recent studies showing a yield of less than 2%. This study aimed to determine the overall positivity rate of CTPA examinations and understand the factors that affect the yield of the CTPA examination.

METHODS

We retrospectively analysed 2713 patients who received the CTPA exam between 2016 and 2018. Type of study ordered (CTPA chest or CTPA chest with abdomen and pelvis CT), patient location (emergency department (ED), outpatient, inpatient, intensive care unit (ICU)) and patient characteristics-age, sex and body mass index (BMI) were recorded. A logistic regression analysis was performed to determine what factors affect the positivity rate of CT scans for pulmonary embolism (PE).

RESULTS

With 296 positive test results, the overall CTPA positivity was 10.9%. Male sex was associated with higher CTPA positivity, gender difference was maximum in 18-year to 35-year age group. Overweight and obese patients had significantly higher positivity as compared with BMI<25 (p<0.05). Higher positivity rate was seen in the BMI 25-40 group (11.9%) as compared with BMI>40 (10.1%) (p<0.05). Significant difference (p<0.001) was also found in CTPA examination yield from ICU (15.3%) versus inpatients (other than ICU) (12.4%) versus ED (9.6%), and outpatients (8.5%). The difference in CTPA yield based on the type of CT order (CTPA chest vs CTPA chest with CT abdomen and pelvis), patient's age and sex was not significant.

CONCLUSION

CTPA yield of 10.9% in this study is comparable to acceptable positivity rate for the USA and is higher than recent studies showing positivity of <2%. Patient characteristics like obesity and ICU or inpatient location are associated with higher rate of CT positivity.

Higher Imaging Yield When Clinical Decision Support Is Used

OBJECTIVE

Increased utilization of CT pulmonary angiography (CTPA) for the evaluation of pulmonary embolism has been associated with decreasing diagnostic yields and rising concerns about the harms of unnecessary testing. The objective of this study was to determine whether clinical decision support (CDS) use would be associated with increased imaging yields after controlling for selection bias.

METHODS

We performed a retrospective cohort study in the emergency departments of two tertiary care hospitals of all CTPAs performed between August 2015 and September 2018. Providers ordering a CTPA are routed to an optional CDS tool, which allows them to use Wells' Criteria for pulmonary embolism. After propensity score matching, CTPA yield was calculated for the CDS-use and CDS-dismissal groups and stratified by provider type.

RESULTS

A total of 7,367 CTPAs were ordered during the study period. Of those, providers used the CDS tool in 2,568 (35%) cases and did not use the tool in 4,799 (65%) of cases. After propensity score matching, CTPA yield was 11.99% in the CDS-use group and 8.70% in the CDS-dismissal group (P < .001). Attending physicians, residents, and physician assistant CDS users demonstrated a 56.5% (P = .006), 38.7% (P = .01), and 16.7% (P = .03) increased yield compared with those who dismissed the tool, respectively.

DISCUSSION

Diagnostic yield was 38% higher for CTPAs when the provider used the CDS tool, after controlling for selection bias. Yields were higher for every provider type. Further research is needed to discover successful strategies to increase provider use of these important tools.

Variability in practice patterns among emergency physicians in the evaluation of patients with a suspected diagnosis of pulmonary embolism

PURPOSE

To describe the inter-physician variability in the utilisation rate and diagnostic yield of computed tomography pulmonary angiography (CTPA) among a group of emergency department (ED) physicians working in a similar clinical environment.

METHODS

We collected data on all CTPA studies ordered by ED physicians at three affiliated sites during a 2-year period between January 1, 2016, and December 31, 2017. For each physician, we calculated individual CTPA utilisation rate (total number of CTPAs ordered per 1000 ED visits) and diagnostic yield (percentage of CTPAs that were positive for PE). Additional analysis was carried out in order to identify the highest orderers of CTPA and their diagnostic yield.

RESULTS

Seventy-seven ED physicians who collectively ordered a total of 2788 CTPAs were included in the study. Utilisation rates ranged from 1.1 to 22.2 CTPA per 1000 ED visits (median: 5.2 CTPA/1000 ED visits; 25%ile: 3.6 CTPA/1000 ED visits; 75%ile: 7.9 CTPA/1000 ED visits) and the CTPA diagnostic yields ranged from 0% to 33% (median: 9.1%; 25%ile: 5.2%; 75%ile: 16.1%). Those physicians in the lower quartile for ordering rate had a higher mean diagnostic yield when compared to the higher quartiles.

CONCLUSION

The findings of this study demonstrate variability in CTPA ordering patterns and diagnostic yields among physicians working within the same clinical environment. There is some suggestion that those physicians who order disproportionately higher numbers of CTPAs have lower diagnostic yields.

Clinical presentation and diagnostic work up of suspected pulmonary embolism in a district hospital emergency centre serving a high HIV/TB burden population

Introduction

The diagnosis of pulmonary embolism (PE) is challenging to make and is often missed in the emergency centre. The diagnostic work-up of PE has been improved by the use of clinical decision rules (CDRs) and CT pulmonary angiography (CTPA) in high-income countries. CDRs have not been validated in the South African environment where HIV and tuberculosis (TB) are highly prevalent. Both conditions are known to induce a hyper-coagulable state. The objective of this study was to describe the clinical presentation and diagnostic workup of suspected PE in our setting and to determine the prevalence of HIV and TB in our sample of patients with confirmed PE.

Methods

This study was a retrospective chart review of patients with suspected PE who had CTPAs performed between October 2013 and October 2015 at a district hospital in Cape Town, South Africa. Data were collected on demographics, presenting signs and symptoms, vitals, bedside investigations, HIV and TB status. A Revised Geneva score (RGS) was calculated retrospectively and compared to the CTPA result.

Results

The median age of patients with confirmed PE was 45 years and 68% were female. The CTPA yield for PE in our study population was 32%. The most common presenting complaint was dyspnoea (83%). Deep venous thrombosis (DVT) was present in 29%. No sign or symptom was observed to be markedly different in patients with confirmed PE vs no PE. Among patients with confirmed PE, 37% were HIV positive and 52% had current TB. RGS compared poorly with CTPA results.

Conclusions

PE remains a diagnostic challenge. In our study, the retrospectively calculated CDR was not predictive of PE in a population with a high prevalence of HIV and TB. Emergency physicians should be cautious when making a clinical probability assessment of PE in this setting. However, further studies are needed to develop a predictive CDR for the local environment.

Baseline Performance of Real-World Clinical Practice Within a Statewide Emergency Medicine Quality Network: The Michigan Emergency Department Improvement Collaborative (MEDIC)

STUDY OBJECTIVE

Large-scale quality and performance measurement across unaffiliated hospitals is an important strategy to drive practice change. The Michigan Emergency Department Improvement Collaborative (MEDIC), established in 2015, has baseline performance data to identify practice variation across 15 diverse emergency departments (EDs) on key emergency care quality indicators.

METHODS

MEDIC is a unique physician-led partnership supported by a major third-party payer. Member sites contribute electronic health record data and trained abstractors add supplementary data for eligible cases. Quality measures include computed tomography (CT) appropriateness for minor head injury, using the Canadian CT Head Rule for adults and Pediatric Emergency Care Applied Network rules for children; chest radiograph use for children with asthma, bronchiolitis, and croup; and diagnostic yield of CTs for suspected pulmonary embolism. Baseline performance was established with statistical process control charts.

RESULTS

From June 1, 2016, to October 31, 2017, the MEDIC registry contained 1,124,227 ED visits, 23.2% for children (<18 years). Overall baseline performance included the following: 40.9% of adult patients with minor head injury (N=11,857) had appropriate CTs (site range 24.3% to 58.6%), 10.3% of pediatric minor head injury cases (N=11,183) exhibited CT overuse (range 5.8% to 16.8%), 38.1% of pediatric patients with a respiratory condition (N=18,190) received a chest radiograph (range 9.0% to 62.1%), and 8.7% of pulmonary embolism CT results (N=16,205) were positive (range 7.5% to 14.3%).

CONCLUSION

Performance varied greatly, with demonstrated opportunity for improvement. MEDIC provides a robust platform for emergency physician engagement across ED practice settings to improve care and is a model for other states.

Retrospective Analysis of Emergency Computed Tomography Imaging Utilization at an Academic Centre: An Analysis of Clinical Indications and Outcomes

Purpose

To explore resource utilization through evaluation of computed tomography (CT) imaging trends in the emergency department by examining common indications/outcomes for imaging in this setting.

Methods

A retrospective analysis of clinical indications/outcomes for all CT imaging in 3 emergency departments over a 1-year period was conducted. Scans were divided by body part and the most common indications for each type of scan were determined. Clinical outcomes from each study were extracted from final interpretations by the reporting radiologist.

Results

A total of 4556 CT scans were performed in the emergency department over a 1-year period. A total of 3.6% of all-comers to our emergency departments underwent CT scan as part of their investigation. There were 2107 head CTs (46%), 1296 (28%) abdominal CTs, 468 (10%) CTs of the chest, 408 (9%) CTs of the neck/spine, and 101 (2%) extremity CTs performed. The most common clinical indication for performing a CT head was focal neurological defect comprising 1534 (73%) of all CT heads. Twenty-four percent of abdominal CTs were for investigation of right lower quadrant pain, followed by flank pain (19%). Chest pain and shortness of breath were the most common indications for CTs of the chest (315 [75%]) with 10% of these examinations for this indication positive for pulmonary embolism. Trauma was the most common indication for neck CTs (296 [73%]) and extremities (70 [69%]). Nil acute was the most common final interpretation in all categories (79% CT heads, 75% neck CTs, 38% abdominal CTs, 43% chest CTs).

Conclusions

Nil acute was the most common diagnosis; however, serious clinical outcomes were identified 40% of the time. Cross-sectional imaging remains an integral tool for triage and diagnosis in this environment as the cost of missing a diagnosis in this setting has a great impact on patient care.

Yield of CT pulmonary angiography in the diagnosis of acute pulmonary embolism: short report

OBJECTIVE

To assess computed tomography pulmonary angiography (CTPA) positive yield rate for pulmonary embolism (PE) in a Canadian academic tertiary center.

RESULTS

This one-center retrospective cross-sectional study includes from 5565 (model 1) to 5296 (model 2) patients that were evaluated for suspected PE in 2015, among which 1331 (23.9% (model 1) to 25.1% (model 2)) underwent CTPA. Mean age of CTPA patients was 60.2 ± 16.6 years, of which 575 were males (43.2%). Two hundred eleven CTPA examinations were positive for PE, giving a CTPA positive yield rate of 15.9% (95% CI (13.93-17.87)). One hundred and thirteen (8.1%) CTPA were considered indeterminate, and eleven were considered nondiagnostic (0.8%). Among the 211 CTPA positive for PE, 67 (32%) were proximal emboli, 98 (47%) were segmental emboli and 44 (21%%) were subsegmental emboli. In conclusion, in this retrospective study done in a Canadian academic tertiary center, we report a positive rate of 15.9% for PE detection with CTPA, which is above the generally accepted lower threshold of 10% for the yield of CTPA.

Computed tomography for suspected pulmonary embolism results in a large number of non-significant incidental findings and follow-up investigations

INTRODUCTION

Computed tomographic pulmonary angiograms (CTPAs) are often ordered to evaluate pulmonary embolism (PE) in the emergency department (ED). The increase use of CTPA has led to an increase in incidental findings, often of low clinical significance. Our objectives were to (1) assess the prevalence and clinical significance of incidental findings identified in patients evaluated with CTPAs for PE in the ED, (2) evaluate follow-up investigations for these incidental findings, and (3) assess the utility of routine chest X-rays done prior to CTPA.

METHODS

This is a historical cohort study of adult patients, presenting to two tertiary care EDs from January-December 2015, evaluated with CTPA for possible PE. Two reviewers' extracted data from electronic CT records in a standardized fashion with inter-rater reliability reported using the kappa statistic. We measured the prevalence of PE and stratified non-PE findings according to alternative diagnoses and incidental findings. Data were reported as mean and standard deviation (SD). Univariate analyses were performed with t test for continuous variables.

RESULTS

A total of 1708 studies were included (mean 62 years (SD 16.7), 56.9% female). PE was found in 233 (13.6%) patients. A total of 223 (13.1%) patients had an incidental finding, the majority of which included pulmonary nodules (n = 83, 37.2%) and adenopathy (n = 26, 11.6%). Of the incidental findings, 197 (88.3%) were non-significant and led to no definitive diagnosis of cancer. In patients who underwent both CTPA and chest X-ray, X-ray reports revealed the same diagnosis in 77% of PE-negative patients without missing a clinically significant incidental finding.

CONCLUSIONS

Incidental findings are as common as a diagnosis of PE in patients undergoing CTPA. They are rarely clinically significant. Chest radiograph remains a reasonable initial investigation as it can aid in identifying alternative diagnoses especially in the setting of a low pre-test probability for PE.

Comparison of the age-adjusted and clinical probability-adjusted D-dimer to exclude pulmonary embolism in the ED

BACKGROUND

Diagnosing pulmonary embolism (PE) in the emergency department (ED) can be challenging because its signs and symptoms are non-specific.

OBJECTIVE

We compared the efficacy and safety of using age-adjusted D-dimer interpretation, clinical probability-adjusted D-dimer interpretation and standard D-dimer approach to exclude PE in ED patients.

DESIGN/METHODS

We performed a health records review at two emergency departments over a two-year period. We reviewed all cases where patients had a D-dimer ordered to test for PE or underwent CT or VQ scanning for PE. PE was considered to be present during the emergency department visit if PE was diagnosed on CT or VQ (subsegmental level or above), or if the patient was subsequently found to have PE or deep vein thrombosis during the next 30 days. We applied the three D-dimer approaches to the low and moderate probability patients. The primary outcome was exclusion of PE with each rule. Secondary objective was to estimate the negative predictive value (NPV) for each rule.

RESULTS

1163 emergency patients were tested for PE and 1075 patients were eligible for inclusion in our analysis. PE was excluded in 70.4% (95% CI 67.6-73.0%), 80.3% (95% CI 77.9-82.6%) and 68.9%; (95% CI 65.7-71.3%) with the age-adjusted, clinical probability-adjusted and standard D-dimer approach. The NPVs were 99.7% (95% CI 99.0-99.9%), 99.1% (95% CI 98.3-99.5%) and 100% (95% CI 99.4-100.0%) respectively.

CONCLUSION

The clinical probability-adjusted rule appears to exclude PE in a greater proportion of patients, with a very small reduction in the negative predictive value.

Imaging of suspected pulmonary embolism and deep venous thrombosis in obese patients

Obesity is a growing problem around the world, and radiology departments frequently encounter difficulties related to large patient size. Diagnosis and management of suspected venous thromboembolism, in particular deep venous thrombosis (DVT) and pulmonary embolism (PE), are challenging even in some lean patients, and can become even more complicated in the setting of obesity. Many obstacles must be overcome to obtain imaging examinations in obese patients with suspected PE and/or DVT, and to ensure that these examinations are of sufficient quality to diagnose or exclude thromboembolic disease, or to establish an alternative diagnosis. Equipment limitations and technical issues both need to be acknowledged and addressed. Table weight limits and scanner sizes that readily accommodate obese and even morbidly obese patients are not in place at many clinical sites. There are also issues with image quality, which can be substantially compromised. We discuss current understanding of the effects of patient size on imaging in general and, more specifically, on the imaging modalities used for the diagnosis and treatment of DVT and PE. Emphasis will be placed on the technical parameters and protocol nuances, including contrast dosing, which are necessary to refine and optimize images for the diagnosis of DVT and PE in obese patients, while remaining cognizant of radiation exposure. More research is necessary to develop consistent high-level evidence regarding protocols to guide radiologists, and to help them effectively utilize emerging technology.

Referral Patterns and Diagnostic Yield of Lung Scintigraphy in the Diagnosis of Acute Pulmonary Embolism

Introduction. The purpose of this study is to assess referral patterns and the yield of ventilation-perfusion (V/Q) scintigraphy in patients referred for acute pulmonary embolism (PE). Methods. We retrospectively reviewed the charts of all patients who underwent V/Q studies between April 1, 2008, and March 31, 2010. Patients were subdivided into 4 groups based on their referral source: emergency department (ED), hospital inpatient ward, outpatient thrombosis clinic, and all other outpatient sources. Results. A total of 1008 patients underwent V/Q scintigraphy to exclude acute PE. The number of ED, inpatient, thrombosis clinic, and outpatient studies was 43 (4.3%), 288 (28.6%), 351 (34.8%), and 326 (32.3%). Proportion of patients with contrast contraindication varied significantly among the different groups. Of the 1,008 studies, 331 (32.8%) were interpreted as normal, 408 (40.5%) as low, 158 (15.7%) as intermediate, and 111 (11.0%) as high probability for PE. 68 (6.7%) patients underwent CTPA within 2 weeks following V/Q. Conclusion. The rate of nondiagnostic studies is lower than that reported in previously published data, with a relatively low rate of intermediate probability studies. Only a small fraction of patients undergoing a V/Q scan will require a CTPA.

Clinical utility and cost analysis of routine postoperative head CT in elective aneurysm clippings

OBJECTIVE

Postoperative head CT scanning is performed routinely at the authors' institution on all neurosurgical patients after elective aneurysm clippings. The goal of this study was to determine how often these scans influence medical management and to quantify the associated imaging costs.

METHODS

The authors reviewed the medical records and accounting database of 304 patients who underwent elective (i.e., nonruptured) aneurysm clipping performed by 1 surgeon (M.T.L.) from 2010 to 2014 at the University of California, San Francisco. Specifically, the total number of postoperative head CT scans, radiographic findings, and the effect of these studies on patient management were determined. The authors obtained the total hospital costs for these patients, including the cost of imaging studies, from the hospital accounting database.

RESULTS

Overall, postoperative CT findings influenced clinical management in 3.6% of cases; specifically, they led to permissive hypertension in 4 patients for possible ischemia, administration of mannitol for edema and high-flow oxygen for pneumocephalus in 2 patients each, seizure prophylaxis in 1 patient, Plavix readjustment in 1 patient, and return to the operating room for an asymptomatic epidural hematoma evacuation in 1 patient. When patients were stratified on the basis of postoperative neurological examination, findings on CT scans altered management in 1.1%, 4.8%, and 9.0% of patients with no new neurological deficits, a nonfocal examination, and focal deficits, respectively. The mean total hospital cost for treating patients who undergo elective aneurysm clipping was $72,227 (± $53,966) (all values are US dollars), and the cost of obtaining a noncontrast head CT scan was $292. Neurologically intact patients required 99 head CT scans, at a cost of $28,908, to obtain 1 head CT scan that influenced medical management. In contrast, patients with a focal neurological deficit required only 11 head CT scans, at a cost of $3212, to obtain 1 head CT scan that changed clinical management.

CONCLUSIONS

Although there are no clear guidelines, the large number and high cost of CT scans needed to treat neurologically intact elective aneurysm patients suggest that careful neurological monitoring may be more clinically useful and a better use of hospital resources than routine postoperative CT.

Increasing use of CTPA for the investigation of suspected pulmonary embolism

OBJECTIVES

Pulmonary embolism (PE) is a frequently suspected life-threatening condition that often presents with non-specific signs and symptoms. There is concern that increased availability of computerized tomography pulmonary angiogram (CTPA) is resulting in overuse in the diagnostic workup of patients presenting with cardio-respiratory symptoms. We therefore aimed to determine whether use of CTPA was increasing over time within our institution, with a consequent decrease in the diagnostic yield of PE. Furthermore, we investigated the frequency of alternative (non-PE) pathological findings revealed by CTPA.

METHODS

All patients who underwent CTPA in the first 15 days of eight consecutive years were enrolled retrospectively. Radiology reports and online medical records were examined. In addition, the rates of incidental PE from patients undergoing CT chest for non-suspected PE indications were also examined.

RESULTS

An increasing use of CTPA was confirmed (p = 0.04). Despite this, the diagnostic yield of PE also increased (p = 0.03). Similarly, increasing numbers of patients underwent CT chest for non-PE indications, but in this group the rate of incidental PE remained static (~3.4%). In CPTA investigations that were negative for PE, common alternative findings were consolidation, pleural effusion and emphysema, with only 16.7% showing no abnormality.

CONCLUSION

Although CTPA use is increasing, so is the diagnostic yield of PE. In contrast, the rate of incidental PE in those undergoing a CT chest scan for non-PE diagnosis remains relatively low and stable. This suggests that our observed increased use of CTPA is clinically appropriate.

RESPECT-ED: Rates of Pulmonary Emboli (PE) and Sub-Segmental PE with Modern Computed Tomographic Pulmonary Angiograms in Emergency Departments: A Multi-Center Observational Study Finds Significant Yield Variation, Uncorrelated with Use or Small PE Rates

INTRODUCTION

Overuse of CT Pulmonary Angiograms (CTPA) for diagnosing pulmonary embolism (PE), particularly in Emergency Departments (ED), is considered problematic. Marked variations in positive CTPA rates are reported, with American 4-10% yields driving most concerns. Higher resolution CTPA may increase sub-segmental PE (SSPE) diagnoses, which may be up to 40% false positive. Excessive use and false positives could increase harm vs. benefit. These issues have not been systematically examined outside America.

AIMS

To describe current yield variation and CTPA utilisation in Australasian ED, exploring potential factors correlated with variation.

METHODS

A retrospective multi-centre review of consecutive ED-ordered CTPA using standard radiology reports. ED CTPA report data were inputted onto preformatted data-sheets. The primary outcome was site level yield, analysed both intra-site and against a nominated 15.3% yield. Factors potentially associated with yield were assessed for correlation.

RESULTS

Fourteen radiology departments (15 ED) provided 7077 CTPA data (94% ≥64-slice CT); PE were reported in 1028 (yield 14.6% (95%CI 13.8-15.4%; range 9.3-25.3%; site variation p <0.0001) with four sites significantly below and one above the 15.3% target. Admissions, CTPA usage, PE diagnosis rates and size of PE were uncorrelated with yield. Large PE (≥lobar) were 55% (CI: 52.1-58.2%) and SSPE 8.8% (CI: 7.1-10.5%) of positive scans. CTPA usage (0.2-1.5% adult attendances) was correlated (p<0.006) with PE diagnosis but not SSPE: large PE proportions.

DISCUSSION/ CONCLUSIONS

We found significant intra-site CTPA yield variation within Australasia. Yield was not clearly correlated with CTPA usage or increased small PE rates. Both SSPE and large PE rates were similar to higher yield historical cohorts. CTPA use was considerably below USA 2.5-3% rates. Higher CTPA utilisation was positively correlated with PE diagnoses, but without evidence of increased proportions of small PE. This suggests that increased diagnoses seem to be of clinically relevant sized PE.

Suboptimal implementation of diagnostic algorithms and overuse of computed tomography-pulmonary angiography in patients with suspected pulmonary embolism

BACKGROUND

Majority of our computed tomography-pulmonary angiography (CTPA) scans report negative findings. We hypothesized that suboptimal reliance on diagnostic algorithms contributes to apparent overuse of this test.

METHODS

A retrospective review was performed on 2031 CTPA cases in a large hospital system. Investigators retrospectively calculated pretest probability (PTP). Use of CTPA was considered as inappropriate when it was ordered for patients with low PTP without checking D-dimer (DD) or following negative DD.

RESULTS

Among the 2031 cases, pulmonary embolism (PE) was found in 7.4% (151 cases). About 1784 patients (88%) were considered "PE unlikely" based on Wells score. Out of those patients, 1084 cases (61%) did not have DD test prior to CTPA. In addition, 78 patients with negative DD underwent unnecessary CTPA; none of them had PE.

CONCLUSIONS

The suboptimal implementation of PTP assessment tools can result in the overuse of CTPA, contributing to ineffective utilization of hospital resources, increased cost, and potential harm to patients.

Yield of CT Pulmonary Angiography in the Emergency Department When Providers Override Evidence-based Clinical Decision Support

Purpose To determine the frequency of, and yield after, provider overrides of evidence-based clinical decision support (CDS) for ordering computed tomographic (CT) pulmonary angiography in the emergency department (ED). Materials and Methods This HIPAA-compliant, institutional review board-approved study was performed at a tertiary care, academic medical center ED with approximately 60 000 annual visits and included all patients who were suspected of having pulmonary embolism (PE) and who underwent CT pulmonary angiography between January 1, 2011, and August 31, 2013. The requirement to obtain informed consent was waived. Each CT order for pulmonary angiography was exposed to CDS on the basis of the Wells criteria. For patients with a Wells score of 4 or less, CDS alerts suggested d-dimer testing because acute PE is highly unlikely in these patients if d-dimer levels are normal. The yield of CT pulmonary angiography (number of positive PE diagnoses/total number of CT pulmonary angiographic examinations) was compared in patients in whom providers overrode CDS alerts (by performing CT pulmonary angiography in patients with a Wells score ≤4 and a normal d-dimer level or no d-dimer testing) (override group) and those in whom providers followed Wells criteria (CT pulmonary angiography only in patients with Wells score >4 or ≤4 with elevated d-dimer level) (adherent group). A validated natural language processing tool identified positive PE diagnoses, with subsegmental and/or indeterminate diagnoses removed by means of chart review. Statistical analysis was performed with the χ² test, the Student t test, and logistic regression. Results Among 2993 CT pulmonary angiography studies in 2655 patients, 563 examinations had a Wells score of 4 or less but did not undergo d-dimer testing and 26 had a Wells score of 4 or less and had normal d-dimer levels. The yield of CT pulmonary angiography was 4.2% in the override group (25 of 589 studies, none with a normal d-dimer level) and 11.2% in the adherent group (270 of 2404 studies) (P < .001). After adjustment for the risk factor differences between the two groups, the odds of an acute PE finding were 51.3% lower when providers overrode alerts than when they followed CDS guidelines. Comparison of the two groups including only patients unlikely to have PE led to similar results. Conclusion The odds of an acute PE finding in the ED when providers adhered to evidence presented in CDS were nearly double those seen when providers overrode CDS alerts. Most overrides were due to the lack of d-dimer testing in patients unlikely to have PE. ^© RSNA, 2016.

Characteristics and clinical value of 3D MR imaging in the diagnosis of pulmonary embolism

The aim of the present study was to investigate the characteristics and value of 3D dynamic contrast-enhanced magnetic resonance pulmonary angiography (3D-DCE-MRPA) for the diagnosis of pulmonary embolism (PE). Among patients suspected with PE, 30 cases were scheduled for 3D-DCE-MRPA [magnetic resonance imaging (MRI) group], and 30 cases were examined using multislice computed tomographic pulmonary angiography (msCTPA) [computed tomography (CT) group]. Direct signs including location, number, morphology of emboli, and indirect signs such as pulmonary infarction, pneumonia and pleural effusion, were analyzed. Pulmonary artery enhancement was observed. Image quality was contrasted, branches of the pulmonary artery revealed, and differences in sensitivity, specificity and signal-to-noise ratio (SNR) were compared. The number and morphology of emboli in the two groups were compared, and there were no significant differences (P>0.05). In the MRI group, significantly more emboli were located in segmental and subsegmental bronchi (P<0.05). The indirect signs in the two groups were compared and the differences were not statistically significant (P>0.05). The difference in image quality between the two groups was not statistically significant (P>0.05). Levels 5 and 6 of the pulmonary artery branch were more evident in the MRI group compared to the CT group. The SNR and carrier-to-noise ratio in the MRI group were significantly higher than those in the CT group (P<0.05). Twenty-six cases of PE were diagnosed in the CT group, with a sensitivity of 90.5% and specificity of 86.7%. Twenty-five cases were diagnosed in the MRI group, with a sensitivity of 92.3% and specificity of 84.2%. In conclusion, 3D-DCE-MRPA surpassed msCTPA in revealing segmental and subsegmental pulmonary artery PE.

CT Pulmonary Angiography: Using Decision Rules in the Emergency Department

PURPOSE

The aim of this study was to assess the appropriateness of utilization and diagnostic yields of CT pulmonary angiography (CTPA), comparing two commonly applied decision rules, the pulmonary embolism (PE) rule-out criteria (PERC) and the modified Wells criteria (mWells), in the emergency department (ED) setting.

METHODS

Institutional review board approval was obtained for this HIPAA-compliant, prospective-cohort, academic single-center study. Six hundred two consecutive adult ED patients undergoing CTPA for suspected PE formed the study population. The outcome was positive or negative for PE by CTPA and at 6-month follow-up. PERC and mWells scores were calculated. A positive PERC score was defined as meeting one or more criteria and a positive mWells score as >4. The percentage of CT pulmonary angiographic examinations that could have been avoided and the diagnostic yield of CTPA using PERC, mWells, and PERC applied to a negative mWells score were calculated.

RESULTS

The diagnostic yield of CTPA was 10% (61 of 602). By applying PERC, mWells, and PERC to negative mWells score, 17.6% (106 of 602), 45% (273 of 602), and 17.1% (103 of 602) of CT pulmonary angiographic examinations, respectively, could have been avoided. The diagnostic yield in PERC-positive patients was higher than in mWells-positive patients (10% [59 of 602] vs 8% [49 of 602], P < .0001). Among PERC-negative and mWells-negative patients, the diagnostic yields for PE were 1.9% (2 of 106) and 4% (12 of 273), respectively (P = .004). The diagnostic yield of a negative PERC score applied to a negative mWells score was 1.9% (2 of 103).

CONCLUSIONS

The use of PERC in the ED has the potential to significantly reduce the utilization of CTPA and misses fewer cases of PE compared with mWells, and it is therefore a more efficient decision tool.

Overdiagnosis of Pulmonary Embolism by Pulmonary CT Angiography

OBJECTIVE

The purpose of this study is to evaluate the rate of overdiagnosis of pulmonary embolism (PE) by pulmonary CT angiography (CTA) in a tertiary-care university hospital.

MATERIALS AND METHODS

This study is a retrospective review of all pulmonary CTA examinations performed in a tertiary-care university hospital over a 12-month period. Studies originally reported as positive for PE were retrospectively reinterpreted by three subspecialty chest radiologists with more than 10 years' experience. A pulmonary CTA was considered negative for PE when all three chest radiologists were in agreement that the pulmonary CTA study was negative for PE. The location and potential causes for PE overdiagnosis were recorded.

RESULTS

A total of 937 pulmonary CTA studies were performed over the study period. PE was diagnosed in the initial report in 174 of these cases (18.6%). There was discordance between the chest radiologists and the original radiologist in 45 of 174 (25.9%) cases. Discordance occurred more often where the original reported PE was solitary (46.2% of reported solitary PEs were considered negative on retrospective review) and located in a segmental or subsegmental pulmonary artery (26.8% of segmental and 59.4% of subsegmental PE diagnoses were considered negative on retrospective review). The most common cause of diagnostic difficulty was breathing motion artifact, followed by beam-hardening artifact.

CONCLUSION

In routine clinical practice, PEs diagnosed by pulmonary CTA are frequently overdiagnosed, when compared with the consensus opinion of a panel of expert chest radiologists. Improvements in the quality of pulmonary CTA examination and increased familiarity with potential diagnostic pitfalls in pulmonary CTA are recommended to minimize misdiagnosis of PE.

Sub-segmental pulmonary embolism in three academic teaching hospitals: a review of management and outcomes

BACKGROUND

The availability of computed tomography pulmonary angiography (CTPA) has led to an increase in the diagnosis of sub-segmental pulmonary embolism (SSPE). Current clinical practice guidelines do not make any treatment distinctions for SSPE, though the benefits of anticoagulation for SSPE have not been established.

OBJECTIVES

To review the frequency of pulmonary embolism and sub-segmental pulmonary embolism identified through CTPA as well as their management.

METHODS

Cross-sectional review of the charts of 2213 patients who underwent CTPA in three Hamilton teaching hospitals from 2009 to 2011. In-depth review of the charts of patients with SSPE was undertaken to determine the frequency with which patients received anticoagulation therapy for SSPE, as well as bleeding complications and recurrent thrombosis.

RESULTS

A total of 2216 CTPAs were reviewed. The frequency of PE was 24.8% (n = 550). The most frequent filling defect was SSPE in 82 patients (3.9% of total scans and 15.0% of identified PEs). In 55 of these 82 SSPEs, an alternative diagnosis to PE was identified on CT to explain the patients' symptoms. Approximately 52.4% (n = 43) received anticoagulation for SSPE. Major life-threatening bleeding complications occurred in two of the 43 who received anticoagulation for SSPE. There was no documented recurrent thrombosis in any patients with SSPE, with or without anticoagulation.

SUMMARY/CONCLUSIONS

A substantial proportion of patients received anticoagulation for SSPE (52%) and two developed life-threatening bleeding complications. Randomized controlled trial data are needed to further investigate the risks and benefits of anticoagulation in patients with SSPE.

High pitch, low voltage dual source CT pulmonary angiography: assessment of image quality and diagnostic acceptability with hybrid iterative reconstruction

Increased use of CT Pulmonary angiography in suspected pulmonary embolism (PE) has driven research to minimize radiation dose while maintaining image quality and diagnostic accuracy. Following institutional review board approval, we performed a retrospective comparison study in patients with suspected PE. Patients were scanned using an ultra high pitch dual source technique (pitch = 2.6) using 120 kV (SVCTPA) (n = 54) or 100 kV (RV-CTPA) (n = 52). SV-CTPA images were reconstructed using filtered back projection (SV-wFBP) and RV-CTPA images were reconstructed using both FBP (RV-wFBP) and Iterative Reconstruction (RV-IR). Comparison of radiation dose, diagnostic ability, subjective image noise, quality, and sharpness, diagnostic agreement, signal to noise (SNR) and contrast to noise ratios (CNR) were performed. Mean effective dose was 2.56 ± 0.19 mSv for the RV protocol compared to 5.36 ± 0.60 mSv for the SV. The RV-CTPA protocol resulted in a mean DLP reduction of 52 % and mean CTDI reduction of 51 %. Pulmonary artery SNR and CNR were significantly higher on RV-IR images than SV-wFBP (p = 0.007, p = 0.003). Mean subjective image noise, quality and sharpness scores did not differ significantly between the SV-wFBP and RVIR images (p > 0.05). Subjective quality scores were significantly better for the RV-IR group compared to the RV-wFBP group (p < 0.001). Agreement between readers for presence or absence of pulmonary emboli on RV-IR images was almost perfect (κ = 0.891, p < 0.001). Iterative reconstruction complements ultra high pitch dual source CTPA examinations acquired using a reduced voltage resulting in higher mean pulmonary artery SNR and CNR when compared to both RV-wFBP and SV-CTPA.