Incidence and Predictors of Repeated Computed Tomographic Pulmonary Angiography in Emergency Department Patients

Knowledge and Perception of Radiation Risk From Computed Tomography Scans Among Patients Attending an Emergency Department

To evaluate the level of knowledge about radiation dose and possible risks related to computed tomography (CT) scans among patients visiting emergency departments (EDs), a survey was conducted over a two-month period. A total of 357 adult patients (44% men and 56% women) presenting for diagnostic imaging in the ED answered a survey consisting of 15 questions. The survey included questions about the participants' demographics and knowledge of radiation. Most of the respondents (58.5%) reported that the physician did not explain the potential risk of radiation before the procedure. In addition, more than half of the respondents (58.1%) expressed feeling anxious about the potential risk of radiation. Most respondents (84.9%) stated that the potential radiation risk did not affect their decision to proceed with the procedure. Overall, the findings highlight a lack of information about radiation and its potential risks provided to patients prior to the diagnostic procedure. Increasing awareness and understanding of the risks associated with these imaging modalities should be considered essential in modern communities. Efforts should be made to ensure that patients undergoing diagnostic imaging are aware of the radiation risks they may encounter.

Role of pulmonary perfusion magnetic resonance imaging for the diagnosis of pulmonary hypertension: A review

Among five types of pulmonary hypertension, chronic thromboembolic pulmonary hypertension (CTEPH) is the only curable form, but prompt and accurate diagnosis can be challenging. Computed tomography and nuclear medicine-based techniques are standard imaging modalities to non-invasively diagnose CTEPH, however these are limited by radiation exposure, subjective qualitative bias, and lack of cardiac functional assessment. This review aims to assess the methodology, diagnostic accuracy of pulmonary perfusion imaging in the current literature and discuss its advantages, limitations and future research scope.

Bedside exclusion of pulmonary embolism in children without radiation (BEEPER): a national study of the Pediatric Emergency Care Applied Research Network-Study protocol

Background

The Pulmonary Embolism Rule Out Criteria (PERC) Peds rule, derived from the PERC rule, was derived to estimate a low pretest probability for pulmonary embolism (PE) in children but has not been prospectively validated.

Objective

The objective of this study was to present a protocol for an ongoing multicenter prospective observational study that evaluates the diagnostic accuracy of the PERC-Peds rule.

Methods

This protocol is identified by the acronym, BEdside Exclusion of Pulmonary Embolism without Radiation in children. The study aims were designed to prospectively validate, or if necessary, refine, the accuracy of PERC-Peds and D-dimer in excluding PE among children with clinical suspicion or testing for PE. Multiple ancillary studies will examine clinical characteristics and epidemiology of the participants. Children aged 4 through 17 years were being enrolled at 21 sites through the Pediatric Emergency Care Applied Research Network (PECARN). Patients taking anticoagulant therapy are excluded. PERC-Peds criteria data, clinical gestalt, and demographic information are collected in real time. The criterion standard outcome is image-confirmed venous thromboembolism within 45 days, determined from independent expert adjudication. We assessed interrater reliability of the PERC-Peds, frequency of PERC-Peds use in routine clinical care, and descriptive characteristics of missed eligible and missed patients with PE.

Results

Enrollment is currently 60% complete with an anticipated data lock in 2025.

Conclusions

This prospective multicenter observational study will not only test whether a set of simple criteria can safely exclude PE without need for imaging but also provide a resource to fill a critical knowledge gap about clinical characteristics of children with suspected and diagnosed PE.

The Effect of Limiting the Scan Range of Computed Tomography Pulmonary Angiography (to Reduce Radiation Exposure) on the Detection of Pulmonary Embolism: A Systematic Review

(1) Background: Computed tomography pulmonary angiography (CTPA) is the standard imaging test for the evaluation of acute pulmonary embolism (PE), but it is associated with patients' exposure to radiation. Studies have suggested that radiation exposure can be reduced without compromising PE detection by limiting the scan range (the z-axis, going from up to down); (2) Methods: A literature search was conducted in MEDLINE and EMBASE on 17 July 2021. Studies were included if they enrolled patients who had undergone a CTPA and described the yield of PE diagnoses, number of missed filling defects and/or other diagnoses using a reduced z-axis in comparison to a full-length scan. To assess risk of bias, we modified an existing risk of bias tools for observational studies, the Newcastle-Ottawa Scale. Results were synthesized in a narrative review. Primary outcomes were the number of missed PE diagnoses (based on at least one filling defect) and filling defects; the secondary outcome was the number of other missed findings; (3) Results: Eleven cohort studies and one case-control study were included reporting on a total of 3955 scans including 1025 scans with a diagnosis of PE. Six different reduced scan ranges were assessed; the most studied was from the top of the aortic arch to below the heart, in which no PEs were missed (seven studies). One sub-segmental PE was missed when the scan coverage was 10 cm starting from the bottom of the aortic arch and 14.7 cm starting from the top of the arch. Five studies that reported on other findings all found that other diagnoses were missed with a reduced z-axis. Most of the included studies had a high risk of bias; (4) Conclusions: CTPA scan coverage reduction from the top of aortic arch to below the heart reduced radiation exposure without affecting PE diagnoses, but studies were generally at high risk of bias.

Guidelines for reasonable and appropriate care in the emergency department (GRACE): Recurrent, low-risk chest pain in the emergency department

This first Guideline for Reasonable and Appropriate Care in the Emergency Department (GRACE-1) from the Society for Academic Emergency Medicine is on the topic: Recurrent, Low-risk Chest Pain in the Emergency Department. The multidisciplinary guideline panel used The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the certainty of evidence and strength of recommendations regarding eight priority questions for adult patients with recurrent, low-risk chest pain and have derived the following evidence based recommendations: (1) for those >3 h chest pain duration we suggest a single, high-sensitivity troponin below a validated threshold to reasonably exclude acute coronary syndrome (ACS) within 30 days; (2) for those with a normal stress test within the previous 12 months, we do not recommend repeat routine stress testing as a means to decrease rates of major adverse cardiac events at 30 days; (3) insufficient evidence to recommend hospitalization (either standard inpatient admission or observation stay) versus discharge as a strategy to mitigate major adverse cardiac events within 30 days; (4) for those with non-obstructive (<50% stenosis) coronary artery disease (CAD) on prior angiography within 5 years, we suggest referral for expedited outpatient testing as warranted rather than admission for inpatient evaluation; (5) for those with no occlusive CAD (0% stenosis) on prior angiography within 5 years, we recommend referral for expedited outpatient testing as warranted rather than admission for inpatient evaluation; (6) for those with a prior coronary computed tomographic angiography within the past 2 years with no coronary stenosis, we suggest no further diagnostic testing other than a single, normal high-sensitivity troponin below a validated threshold to exclude ACS within that 2 year time frame; (7) we suggest the use of depression and anxiety screening tools as these might have an effect on healthcare use and return emergency department (ED) visits; and (8) we suggest referral for anxiety or depression management, as this might have an impact on healthcare use and return ED visits.

Effectiveness of Clinical Decision Tools in Predicting Pulmonary Embolism

Objective

The Wells criteria and revised Geneva score are two commonly used clinical decision tools (CDTs) developed to assist physicians in determining when computed tomographic angiograms (CTAs) should be performed to evaluate the high index of suspicion for pulmonary embolism (PE). Studies have shown varied accuracy in these CDTs in identifying PE, and we sought to determine their accuracy within our patient population.

Methods

Patients admitted to the Emergency Department (ED) who received a CTA for suspected PE from 2019 Jun 1 to 2019 Aug 31 were identified. Two CDTSs, the Wells criteria and revised Geneva score, were calculated based on data available prior to CTA and using the common D-Dimer cutoff of >500 μg/L. We determined the association between confirmed PE and CDT values and determined the association between the D-Dimer result and PE.

Results

392 CTAs were identified with 48 (12.1%) positive PE cases. The Wells criteria and revised Geneva score were significantly associated with PE but failed to identify 12.5% and 70.4% of positive PE cases, respectively. Within our cohort, a D-Dimer cutoff of >300 μg/L was significantly associated with PE and captured 95.2% of PE cases.

Conclusions

Both CDTs were significantly associated with PE but failed to identify PE in a significant number of cases, particularly the revised Geneva score. Alternative D-Dimer cutoffs may provide better accuracy in identifying PE cases.

Perception of Physician Empathy Varies With Educational Level and Gender of Patients Undergoing Low-Yield Computerized Tomographic Imaging

OBJECTIVE

Lack of empathic communication between providers and patients may contribute to low value diagnostic testing in emergency care. Accordingly, we measured the perception of physician empathy and trust in patients undergoing low-value computed tomography (CT) in the emergency department (ED).

METHODS

Multicenter study of ED patients undergoing CT scanning, acknowledged by ordering physicians as unlikely to show an emergent condition. Near the end of their visit, patients completed the Jefferson Scale of Patient Perception of Physician Empathy (JSPPPE), Trust in Physicians Survey (TIPS), and the Group Based Medical Mistrust Scale (GBMMS). We stratified results by patient demographics including gender, race, and education.

RESULTS

We enrolled 305 participants across 9 sites with diverse geographic, racial, and ethnic representation. The median scores (interquartile ranges) for the JSPPPE, TIPS, and GBMMS for all patients were 29 (24-33.5), 55 (47-62), and 18 (12-29). Compared with white patients, nonwhite patients had similar JSPPPE and TIPS scores but had higher (worse) GBMMS scores. Females had significantly lower JSPPPE and TIPS scores than males, and scores were lower (worse) in females with college degrees. Patients in the lowest tier of educational status had the highest (better) JSPPPE and TIPS scores. Scores were invariant with physician characteristics.

CONCLUSION

Among patients undergoing low-value CT scanning in the ED, the degree of patient perception of physician empathy and trust varied based on the patients' level of education and gender. Given this variation, an intervention to increase patient perception of physician empathy should contain individualized strategies to address these subgroups, rather than a one-size-fits-all approach.

Predictive Value of Noncontrast Head CT with Negative Findings in the Emergency Department Setting

BACKGROUND AND PURPOSE

Noncontrast head CTs are routinely acquired for patients with neurologic symptoms in the emergency department setting. Anecdotally, noncontrast head CTs performed in patients with prior negative findings with the same clinical indication are of low diagnostic yield. We hypothesized that the rate of acute findings in noncontrast head CTs performed in patients with a preceding study with negative findings would be lower compared with patients being imaged for the first time.

MATERIALS AND METHODS

We retrospectively evaluated patients in the emergency department setting who underwent noncontrast head CTs at our institution during a 4-year period, recording whether the patient had undergone a prior noncontrast head CT, the clinical indication for the examination, and the examination outcome. Positive findings on examinations were defined as those that showed any intracranial abnormality that would necessitate a change in acute management, such as acute hemorrhage, hydrocephalus, herniation, or interval worsening of a prior finding.

RESULTS

During the study period, 8160 patients in the emergency department setting underwent a total of 9593 noncontrast head CTs; 88.2% (7198/8160) had a single examination, and 11.8% (962/8160) had at least 1 repeat examination. The baseline positive rate of the "nonrepeat" group was 4.3% (308/7198). The 911 patients in the "repeat" group with negative findings on a baseline/first CT had a total of 1359 repeat noncontrast head CTs during the study period. The rate of positive findings for these repeat examinations was 1.8% (25/1359), significantly lower than the 4.3% baseline rate (P < .001). Of the repeat examinations that had positive findings, 80% (20/25) had a study indication that was discordant with that of the prior examination, compared with only 44% (593/1334) of the repeat examinations that had negative findings (P < .001).

CONCLUSIONS

In a retrospective observational study based on approximately 10,000 examinations, we found that serial noncontrast head CT examinations in patients with prior negative findings with the same study indication are less likely to have positive findings compared with first-time examinations or examinations with a new indication. This finding suggests a negative predictive value of a prior noncontrast head CT examination with negative findings with the same clinical indication.

Over-Testing for Suspected Pulmonary Embolism in American Emergency Departments: The Continuing Epidemic

BACKGROUND

No recent data have investigated rates of diagnostic testing for pulmonary embolism (PE) in US emergency departments (EDs), and no data have examined computed tomographic pulmonary angiography (CTPA) rates in subgroups at high risk for adverse imaging outcomes, including young women and children. We hypothesized that over-testing for PE remains a problem.

METHODS AND RESULTS

We used electronic health record and billing data for 16 EDs in Indiana and 11 hospitals in the Dallas-Fort Worth area from 2016 to 2019 to locate ED patients who had any of the following: D-dimer, CTPA, scintillation ventilation perfusion lung scanning or formal pulmonary angiography. The primary outcomes were ED encounter volume-adjusted CTPA rate, PE yield rate with subgroup reporting for children (<18 years) and women under 45 years. We also examined the most frequent diagnoses. From a total visit volume of 1 828 010 patient encounters, 97 125 (5.3% of the total volume) had a diagnostic test for PE, including 25 870 patients who had CTPA order without D-dimer (59% of all tests for PE). The yield rate for PE from CTPA scans was 1.3% (1.1%-1.5%) in Indiana and 4.8% (4.2%-5.1%) in Dallas-Fort Worth (pooled rate 3.1%). Linear regression showed that increased D-dimer ordering correlated with increased PE yield rate (Pearson's R²=0.43; P<0.001). From the pooled sample, 59% of CTPAs done were in women, with 21% of all CTPAs performed on women under 45 years of age, and 1.4% (1.3%-1.5%) on children. The most frequent diagnoses were symptom-based descriptions of chest pain (34%) and shortness of breath (6.5%) and the condition-based diagnosis of pneumonia (4.1%).

CONCLUSIONS

Over-testing for PE in American EDs remains a major public health problem. Centers with higher D-dimer ordering had higher yield of PE on CTPA. These data suggest the potential for implementation of D-dimer based protocols to reduce low-yield CTPA ordering.

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.

Downstream Imaging Utilization After MR Angiography Versus CT Angiography for the Initial Evaluation of Pulmonary Embolism

OBJECTIVE

To compare the proportion of emergency department (ED) patients who undergo subsequent chest CT or MR within 1 year of an initially negative scan for pulmonary embolism (PE).

METHODS

This single-center, retrospective, observational study examined the use of chest CT or MR for ED patients with MR angiography (MRA) negative for PE during April 2008 to March 2013. We compared the 1-year scan utilization for these cases to an age- and sex-matched cohort of patients who underwent CT angiography (CTA). We also calculated time to first follow-up scan and mean radiation dose in each arm. Trained data abstractors used a standardized protocol and electronic case report form to gather all outcomes of interest. Results are reported as means or proportions with their associated confidence intervals (CIs).

RESULTS

In all, 717 ED patients (430 MRAs and 287 CTAs) were included. At 1 year, the proportion undergoing subsequent imaging (MRA 16.7%, CTA 15.3%; difference = 1.4%, 95% CI 4.05%-6.86%) and time to first follow-up scan (difference = 13 days, 95% CI -22.69-48.7) did not differ between arms. Mean radiation dose per patient at 1 year was significantly higher in the CTA arm (9.82 mSv; 95% CI 9.12-10.53) compared with 2.92 mSv (95% CI 1.86-3.98) with MRA. Those with an index MRA were more likely to undergo subsequent MRAs (odds ratio 3.68; 95% CI 1.22-11.12) than those with an index CTA. However, in both arms, the majority (85%) of subsequent scans were CTAs.

CONCLUSIONS

When comparing patients initially undergoing MRA versus CTA for the evaluation of PE, there was no difference in downstream chest CT or MR use at 1 year.

Pulmonary embolism rule-out criteria (PERC) rule in European patients with low implicit clinical probability (PERCEPIC): a multicentre, prospective, observational study

BACKGROUND

The ability of the pulmonary embolism rule-out criteria (PERC) to exclude pulmonary embolism without further testing remains debated outside the USA, especially in the population with suspected pulmonary embolism who have a high prevalence of the condition. Our main objective was to prospectively assess the predictive value of negative PERC to rule out pulmonary embolism among European patients with low implicit clinical probability.

METHODS

We did a multicentre, prospective, observational study in 12 emergency departments in France and Belgium. We included consecutive patients aged 18 years or older with suspected pulmonary embolism. Patients were excluded if they had already been hospitalised for more than 2 days, had curative anticoagulant therapy in progress for more than 48 h, or had a diagnosis of thromboembolic disease documented before admission to emergency department. Physicians completed a standardised case report form comprising implicit clinical probability assessment (low, moderate, or high) and a list of risk factors including criteria of the PERC rule. They were asked to follow international recommendations for diagnostic strategy, masked to PERC assessment. The primary endpoint was the proportion of patients with low implicit clinical probability and negative PERC who had venous thromboembolic events, diagnosed during initial diagnostic work-up or during 3-month follow-up, as externally adjudicated by an independent committee masked to the PERC and clinical probability assessment. The upper limit of the 95% CI around the 3-month thromboembolic risk was set at 3%. We did all analyses by intention to treat, including all patients with complete follow-up. This trial is registered with ClinicalTrials.gov, number NCT02360540.

FINDINGS

Between May 1, 2015, and April 30, 2016, 1773 consecutive patients with suspected pulmonary embolism were prospectively assessed for inclusion, of whom 1757 were included. 1052 (60%) patients were classed as having low clinical probability, 49 (4·7%, 95% CI 3·5-6·1) of whom had a venous thromboembolic event. In patients with a low implicit clinical probability, 337 (32%) patients had negative PERC, of whom four (1·2%; 95% CI 0·4-2·9) went on to have a pulmonary embolism.

INTERPRETATION

In European patients with low implicit clinical probability, PERC can exclude pulmonary embolism with a low percentage of false-negative results. The results of our prospective, observational study allow and justify an implementation study of the PERC rule in Europe.

FUNDING

French Ministry of Health.

The Economic Value of Hybrid Single-photon Emission Computed Tomography With Computed Tomography Imaging in Pulmonary Embolism Diagnosis

Objective

The objective was to quantify the potential economic value of single‐photon emission computed tomography (SPECT) with computed tomography (CT; SPECT/CT) versus CT pulmonary angiography (CTPA), ventilation–perfusion (V/Q) planar scintigraphy, and V/Q SPECT imaging modalities for diagnosing suspected pulmonary embolism (PE) patients in an emergency setting.

Methods

An Excel‐based simulation model was developed to compare SPECT/CT versus the alternate scanning technologies from a payer's perspective. Clinical endpoints (diagnosis, treatment, complications, and mortality) and their corresponding cost data (2016 USD) were obtained by performing a best evidence review of the published literature. Studies were pooled and parameters were weighted by sample size. Outcomes measured included differences in 1) excess costs, 2) total costs, and 3) lives lost per annum between SPECT/CT and the other imaging modalities. One‐way (±25%) sensitivity and three scenario analyses were performed to gauge the robustness of the results.

Results

For every 1,000 suspected PE patients undergoing imaging, expected annual economic burden by modality was found to be 3.2 million (SPECT/CT), 3.8 million (CTPA), 5.8 million (planar), and 3.6 million (SPECT) USD, with a switch to SPECT/CT technology yielding per‐patient‐per‐month cost savings of $51.80 (vs. CTPA), $213.80 (vs. planar), and $36.30 (vs. SPECT), respectively. The model calculated that the incremental number of lives saved with SPECT/CT was six (vs. CTPA) and three (vs. planar). Utilizing SPECT/CT as the initial imaging modality for workup of acute PE was also expected to save $994,777 (vs. CTPA), $2,852,014 (vs. planar), and $435,038 (vs. SPECT) in “potentially avoidable”’ excess costs per annum for a payer or health plan.

Conclusion

Compared to the currently available scanning technologies for diagnosing suspected PE, SPECT/CT appears to confer superior economic value, primarily via improved sensitivity and specificity and low nondiagnostic rates. In turn, the improved diagnostic accuracy accords this modality the lowest ratio of expenses attributable to potentially avoidable complications, misdiagnosis, and underdiagnosis.

D-Dimer Use and Pulmonary Embolism Diagnosis in Emergency Units: Why Is There Such a Difference in Pulmonary Embolism Prevalence between the United States of America and Countries Outside USA?

OBJECTIVE

Although diagnostic guidelines are similar, there is a huge difference in pulmonary embolism (PE) prevalence between the United States of America (US) and countries outside the USA (OUS) in the emergency care setting. In this study, we prospectively analyze patients' characteristics and differences in clinical care that may influence PE prevalence in different countries.

METHODS

An international multicenter prospective diagnostic study was conducted in a standard-of-care setting. Consecutive outpatients presenting to the emergency unit and suspected for PE were managed using the Wells score, STA-Liatest® D-Dimers and imaging.

RESULTS

The prevalence of PE in the study was 7.9% in low and moderate risk patients. Among the 1060 patients with low or moderate pre-test probability (PTP), PE prevalence was four times higher in OUS (10.7%) than in the US (2.5%) (P < 0.0001). The mean number of imaging procedures performed for one new PE diagnosis was 3.3 in OUS vs 17 in the US (P < 0.001). Stopping investigation in the case of negative D-dimers (DD combined) with low/moderate PTP was more frequent in OUS (92.7%) than in the US (75.7%) (P < 0.01). Moreover, the use of imaging was much higher in the US (44.4% vs 19.2% in OUS) in the case of moderate PTP combined with negative DD.

CONCLUSION

Differences between US and OUS PE prevalence in emergency setting might be explained by differences in patients' characteristics and mostly in care patterns. US physicians performed computed tomographic pulmonary angiography more often than in Europe in cases of low/moderate PTP combined with negative DD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01221805.

Follow-up CT pulmonary angiograms in patients with acute pulmonary embolism

Computed tomographic (CT) angiography is associated with a non-negligible lifetime attributable risk of cancer. The risk is considerably greater for women and younger patients. Recognizing that there are risks from radiation, the purpose of this investigation was to assess the frequency of follow-up CT angiograms in patients with acute pulmonary embolism. This was a retrospective cohort study of patients aged ≥18 years with acute pulmonary embolism seen in three emergency departments from January 2013 to December 2014. Records of all patients were reviewed for at least 14 months. Pulmonary embolism was diagnosed by CT angiography in 600 patients. At least one follow-up CT angiogram in 1 year was obtained in 141 of 600 (23.5 %). Two follow-ups in 1 year were obtained in 40 patients (6.7 %), 3 follow-ups were obtained in 15 patients (2.5 %), and 4 follow-ups were obtained in 3 patients (0.5 %). Among young women (aged ≤29 years) with pulmonary embolism, 10 of 21 (47.6 %) had at least 1 follow-up and 4 of 21 (19.0 %) had 2 or more follow-ups in 1 year. Among all patients, recurrent pulmonary embolism was diagnosed in 15 of 141 (10.6 %) on the first follow-up CT angiogram and in 6 of 40 (15.0 %) on the second follow-up. Follow-up CT angiograms were obtained in a significant proportion of patients with pulmonary embolism, including young women, the group with the highest risk. Alternative options might be considered to reduce the hazard of radiation-induced cancer, particularly in young women.

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.

Risk of pulmonary embolism after a prior negative CT pulmonary angiogram

CONTEXT

With increasing utilization of computed tomography pulmonary angiography (CTPA) for the diagnosis of pulmonary embolism (PE), many patients undergo repeat CTs.

OBJECTIVE

The aim of this study is to identify the rate of positive subsequent CTPAs after an initial negative CTPA and whether there is a risk-free period after a negative CTPA.

METHODS

We evaluated 318 patients with at least 1 subsequent CTPA after an initial negative CTPA, with 786 total CTPAs. We also evaluated a control group of 200 unselected CTPAs.

RESULTS

The positive rate in the repeat group was 7% at the first repeat CTPA and 10% per-patient within 1000 days. The positive rate in the control group was 9% (P= not significant). No risk-free period was seen, with a positive rate of 5% within 2 weeks after a negative CTPA. The number of prior negative CTPAs showed a trend towards decreasing rate of the subsequent CTPA being positive, but this did not meet statistical significance.

DISCUSSION

There is no risk-free period after an initial negative CTPA, and therefore, patients with clinical suspicion of PE should be rescanned even after a recent negative study. Even patients with multiple negative prior CTPAs have a measurable risk of subsequent PE. Established clinical prediction scoring systems must be used to triage the patients who need CTPAs.

Radiation doses to emergency department patients undergoing computed tomography

OBJECTIVES

Computed tomography (CT) use is increasing in the emergency department (ED). Many physicians are concerned about exposing patients to radiation from CT scanning, but estimates of radiation doses vary. This study's objective was to determine the radiation doses from CT scanning for common indications in a Canadian ED using modern multidetector CT scanners.

METHODS

We conducted a health records review of consecutive adult patients seen at two busy tertiary care EDs over a 2-month period who underwent CT scanning ordered by emergency physicians. Cases were identified by searching an imaging database. Data collected included patient age and sex, study indication, scanner model, body area, and reported dose-length product. Effective dose per scan was calculated from reported dose-length product. Data were collected on a standardized form, entered into an electronic database, and analyzed with descriptive statistics and 95% CIs.

RESULTS

During the study period, emergency physicians assessed 19,880 patients. Overall, 2,720 (13.7%) underwent CT scanning, and of these, 144 (5.3%) patients had more than one scan. Patients had a mean age of 59.0 years, and 45.3% were men. Mean doses for the most common indications were as follows: simple head, 2.9 mSv; cervical spine, 5.7 mSv; complex head, 9.3 mSv; CT pulmonary angiogram, 11.2 mSv; abdomen (nontraumatic abdominal pain), 15.4 mSv; and abdomen (renal colic), 9.8 mSv.

CONCLUSIONS

Approximately one in seven ED patients had a CT scan. Emergency physicians should be aware of typical radiation doses for the studies they order and how the dose varies by protocol and indication.

Evaluation of Patients With Suspected Acute Pulmonary Embolism: Best Practice Advice From the Clinical Guidelines Committee of the American College of Physicians

DESCRIPTION

Pulmonary embolism (PE) can be a severe disease and is difficult to diagnose, given its nonspecific signs and symptoms. Because of this, testing patients with suspected acute PE has increased dramatically. However, the overuse of some tests, particularly computed tomography (CT) and plasma d-dimer measurement, may not improve care while potentially leading to patient harm and unnecessary expense.

METHODS

The literature search encompassed studies indexed by MEDLINE (1966-2014; English-language only) and included all clinical trials and meta-analyses on diagnostic strategies, decision rules, laboratory tests, and imaging studies for the diagnosis of PE. This document is not based on a formal systematic review, but instead seeks to provide practical advice based on the best available evidence and recent guidelines. The target audience for this paper is all clinicians; the target patient population is all adults, both inpatient and outpatient, suspected of having acute PE.

BEST PRACTICE ADVICE 1

Clinicians should use validated clinical prediction rules to estimate pretest probability in patients in whom acute PE is being considered.

BEST PRACTICE ADVICE 2

Clinicians should not obtain d-dimer measurements or imaging studies in patients with a low pretest probability of PE and who meet all Pulmonary Embolism Rule-Out Criteria.

BEST PRACTICE ADVICE 3

Clinicians should obtain a high-sensitivity d-dimer measurement as the initial diagnostic test in patients who have an intermediate pretest probability of PE or in patients with low pretest probability of PE who do not meet all Pulmonary Embolism Rule-Out Criteria. Clinicians should not use imaging studies as the initial test in patients who have a low or intermediate pretest probability of PE.

BEST PRACTICE ADVICE 4

Clinicians should use age-adjusted d-dimer thresholds (age × 10 ng/mL rather than a generic 500 ng/mL) in patients older than 50 years to determine whether imaging is warranted.

BEST PRACTICE ADVICE 5

Clinicians should not obtain any imaging studies in patients with a d-dimer level below the age-adjusted cutoff.

BEST PRACTICE ADVICE 6

Clinicians should obtain imaging with CT pulmonary angiography (CTPA) in patients with high pretest probability of PE. Clinicians should reserve ventilation-perfusion scans for patients who have a contraindication to CTPA or if CTPA is not available. Clinicians should not obtain a d-dimer measurement in patients with a high pretest probability of PE.

Risk Acceptance and Desire for Shared Decision Making in Pediatric Computed Tomography Scans: A Survey of 350

OBJECTIVE

The dual goals of this study were to assess the level of radiation risk parents are comfortable with and also whether they expect a shared decision making conversation.

METHODS

A convenience sample of adult patients in the emergency department was surveyed. Participants were educated regarding the associated radiation risk with computed tomography (CT) scans. They were then surveyed about their willingness to accept the risk of radiation exposure to their children given varying degrees of pretest probability of a clinically significant finding. Additionally, participants were surveyed regarding whether a physician should provide shared decision making.

RESULTS

A total of 350 surveys were collected. For low, moderate, and high pretest probability of a positive finding on CT, the proportion of participants who would want a CT for their child was 37% (95% confidence interval [95% CI], 32-43%), 70% (95% CI, 65-75%), and 89% (95% CI, 85-92%), respectively. If the likelihood of a positive CT scan was very low (<5%), 24% (95% CI, 20-29%) were willing to have the study performed on their child. Participants would not want a CT for their child regardless of the probability of finding significant pathology in 9% of those surveyed (28/315). Participants wanted a physician to counsel them before ordering a potentially dangerous test in 93% of the surveys. In a test with an estimated 1:1000 risk of cancer, 91% of participants felt that a doctor should always discuss the risk before ordering the study.

CONCLUSIONS

Parents are less willing to accept the risk of radiation from CT scan on their child as the likelihood of positive findings decrease. Parents overwhelmingly want an informed discussion before getting a potentially dangerous test.

Derivation of a screening tool to identify patients with right ventricular dysfunction or tricuspid regurgitation after negative computerized tomographic pulmonary angiography of the chest

Many dyspneic patients who undergo computerized tomographic pulmonary angiography (CTPA) for presumed acute pulmonary embolism (PE) have no identified cause for their dyspnea yet have persistent symptoms, leading to more CTPA scanning. Right ventricular (RV) dysfunction or overload can signal treatable causes of dyspnea. We report the rate of isolated RV dysfunction or overload after negative CTPA and derive a clinical decision rule (CDR). We performed secondary analysis of a multicenter study of diagnostic accuracy for PE. Inclusion required persistent dyspnea and no PE. Echocardiography was ordered at clinician discretion. A characterization of isolated RV dysfunction or overload required normal left ventricular function and RV hypokinesis, or estimated RV systolic pressure of at least 40 mmHg. The CDR was derived from bivariate analysis of 97 candidate variables, followed by multivariate logistic regression. Of 647 patients, 431 had no PE and persistent dyspnea, and 184 (43%) of these 431 had echocardiography ordered. Of these, 64 patients (35% [95% confidence interval (CI): 28%-42%]) had isolated RV dysfunction or overload, and these patients were significantly more likely to have a repeat CTPA within 90 days (P = .02, [Formula: see text] test). From univariate analysis, 4 variables predicted isolated RV dysfunction: complete right bundle branch block, normal CTPA scan, active malignancy, and CTPA with infiltrate, the last negatively. Logistic regression found only normal CTPA scanning significant. The final rule (persistent dyspnea + normal CTPA scan) had a positive predictive value of 53% (95% CI: 37%-69%). We conclude that a simple CDR consisting of persistent dyspnea plus a normal CTPA scan predicts a high probability of isolated RV dysfunction or overload on echocardiography.

Cost-effectiveness of quantitative pretest probability intended to reduce unnecessary medical radiation exposure in emergency department patients with chest pain and dyspnea

OBJECTIVES

Quantitative pretest probability (qPTP) incorporated into a decision support tool with advice can reduce unnecessary diagnostic testing among patients with symptoms suggestive of acute coronary syndrome (ACS) and pulmonary embolism (PE), reducing 30-day costs without an increase in 90-day adverse outcomes. This study estimates long-term (beyond 90-day) costs and outcomes associated with qPTP. The authors hypothesized that qPTP reduces lifetime costs and improves outcomes in low-risk patients with symptoms suggestive of ACS and PE.

METHODS

This was a cost-effectiveness analysis of a multicenter, randomized controlled trial of adult emergency patients with dyspnea and chest pain, in which a clinician encountering a low-risk patient with symptoms suggestive of ACS or PE conducted either the intervention (qPTP for ACS and PE with advice) or the sham (no qPTP and no advice). Effect of the intervention over a patient's lifetime was assessed using a Markov microsimulation model. Short-term costs and outcomes were from the trial; long-term outcomes and costs were from the literature. Outcomes included lifetime transition to PE, ACS, and intracranial hemorrhage (ICH); mortality from cancer, ICH, PE, ACS, renal failure, and ischemic stroke; quality-adjusted life-years (QALYs); and total medical costs compared between simulated intervention and sham groups.

RESULTS

Markov microsimulation for a 40-year-old patient receiving qPTP found lifetime cost savings of $497 for women and $528 for men, associated with small gains in QALYs (2 and 6 days, respectively) and lower rates of cancer mortality in both sexes, but a reduction in ICH only in males. Sensitivity analysis for patients aged 60 years predicted that qPTP would continue to save costs and also reduce mortality from both ICH and cancer. Use of qPTP significantly reduced the lifetime probability of PE diagnosis, with lower probability of death from PE in both sexes aged 40 to 60 years. However, use of qPTP reduced the rate of ACS diagnosis and death from ACS at age 40, but increased the death rate from ACS at age 60 for both sexes.

CONCLUSIONS

Widespread use of a combined qPTP for both ACS and PE has the potential to decrease costs by reducing diagnostic testing, while improving most long-term outcomes in emergency patients with chest pain and dyspnea.

Independent evaluation of a simple clinical prediction rule to identify right ventricular dysfunction in patients with shortness of breath

BACKGROUND

Many patients have unexplained persistent dyspnea after negative computed tomographic pulmonary angiography (CTPA). We hypothesized that many of these patients have isolated right ventricular (RV) dysfunction from treatable causes. We previously derived a clinical decision rule (CDR) for predicting RV dysfunction consisting of persistent dyspnea and normal CTPA, finding that 53% of CDR-positive patients had isolated RV dysfunction. Our goal is to validate this previously derived CDR by measuring the prevalence of RV dysfunction and outcomes in dyspneic emergency department patients.

METHODS

A secondary analysis of a prospective observational multicenter study that enrolled patients presenting with suspected PE was performed. We included patients with persistent dyspnea, a nonsignificant CTPA, and formal echo performed. Right ventricular dysfunction was defined as RV hypokinesis and/or dilation with or without moderate to severe tricuspid regurgitation.

RESULTS

A total of 7940 patients were enrolled. Two thousand six hundred sixteen patients were analyzed after excluding patients without persistent dyspnea and those with a significant finding on CTPA. One hundred ninety eight patients had echocardiography performed as standard care. Of those, 19% (95% confidence interval [CI], 14%-25%) and 33% (95% CI, 25%-42%) exhibited RV dysfunction and isolated RV dysfunction, respectively. Patients with isolated RV dysfunction or overload were more likely than those without RV dysfunction to have a return visit to the emergency department within 45 days for the same complaint (39% vs 18%; 95% CI of the difference, 4%-38%).

CONCLUSION

This simple clinical prediction rule predicted a 33% prevalence of isolated RV dysfunction or overload. Patients with isolated RV dysfunction had higher recidivism rates and a trend toward worse outcomes.

Outcomes and radiation exposure of emergency department patients with chest pain and shortness of breath and ultralow pretest probability: a multicenter study

STUDY OBJECTIVE

Excessive radiation exposure remains a concern for patients with symptoms suggesting acute coronary syndrome and pulmonary embolism but must be judged in the perspective of pretest probability and outcomes. We quantify and qualify the pretest probability, outcomes, and radiation exposure of adults with both chest pain and dyspnea.

METHODS

This was a prospective, 4-center, outcomes study. Patients were adults with dyspnea and chest pain, nondiagnostic ECGs, and no obvious diagnosis. Pretest probability for both acute coronary syndrome and pulmonary embolism was assessed with a validated method; ultralow risk was defined as pretest probability less than 2.5% for both acute coronary syndrome and pulmonary embolism. Patients were followed for diagnosis and total medical radiation exposure for 90 days.

RESULTS

Eight hundred forty patients had complete data; 23 (3%) had acute coronary syndrome and 15 (2%) had pulmonary embolism. The cohort received an average of 4.9 mSv radiation to the chest, 48% from computed tomography pulmonary angiography. The pretest probability estimates for acute coronary syndrome and pulmonary embolism were less than 2.5% in 227 patients (27%), of whom 0 of 277 (0%; 95% confidence interval 0% to 1.7%) had acute coronary syndrome or pulmonary embolism and 7 of 227 (3%) had any significant cardiopulmonary diagnosis. The estimated chest radiation exposure per patient in this ultralow-risk group was 3.5 mSv, including 26 (3%) with greater than 5 mSv radiation to the chest and no significant cardiopulmonary diagnosis.

CONCLUSION

One quarter of patients with chest pain and dyspnea had ultralow risk and no acute coronary syndrome or pulmonary embolism but were exposed to an average of 3.5 mSv radiation to the chest. These data can be used in a clinical guideline to reduce radiation exposure.

Iterative reconstructed ultra high pitch CT pulmonary angiography with cardiac bowtie-shaped filter in the acute setting: effect on dose and image quality

PURPOSE

To evaluate the effect of a cardiac bowtie-shaped filter in an ultra high pitch CTPA protocol at 100 kV on image quality and radiation dose.

MATERIALS AND METHODS

Retrospective study of 100 patients referred for CTPA. 50 patients scanned with a standard 100 kV protocol at pitch 2.8 (Protocol A) and 50 patients scanned with a 100 kV protocol at pitch 3.2 with a cardiac bowtie-shaped filter (Protocol B). All other scanning parameters kept constant. Images from both groups reconstructed with filtered back projection and iterative reconstruction. Central pulmonary vessel attenuation and background noise were quantitatively measured and signal-to-noise (SNR) and contrast-to-noise (CNR) were calculated. Two radiologists performed qualitative assessment grading visualization of the pulmonary vasculature and noise level. CTDIvol and DLP were recorded and effective dose was calculated.

RESULTS

CTDIvol, DLP and effective dose were significantly (p<0.0001) lower in Protocol B (2.3 ± 0.5 mGy, 78.4 ± 16.5 mGycm, 1.4 ± 0.3 mSy, respectively) compared to Protocol A (4.3 ± 0.5 mGy, 152.0 ± 19.6 mGycm, 2.7 ± 0.3 mSy, respectively). Protocol B had significantly (p<0.0001) higher noise than Protocol A (23.8 ± 6.9 HU vs 36.8 ± 7.3 HU) and lower SNR (11.8 ± 3.7 HU vs 19.2 ± 8.1 HU) and CNR (10.3 ± 3.7 HU vs 24.9 ± 13.4 HU) but there was no significant difference in the subjective visualization of the pulmonary vasculature (p=0.63). Furthermore, iterative reconstruction significantly (p<0.0001) improves image noise (29.4 ± 5.5 HU from 36.8 ± 7.3 HU).

CONCLUSION

The addition of a cardiac bowtie-shaped filter with an ultra high pitch CTPA protocol at 100 kV resulted in a 48% dose reduction without significantly affecting diagnostic image quality. In addition, the use of iterative reconstruction significantly improves image quality by reducing noise permitting the possibility for further dose reduction strategies.

Relationship between the use of new or used computed tomography scanners and image retake rates in South Korea

BACKGROUND

The use of high-cost imaging has increased worldwide, contributing to increased healthcare expenditures. Without proper quality verification, the installation of used imaging equipment may lead to wasteful increases in cost due to ineffective and poor-quality imaging that requires repeat scans.

PURPOSE

To examine the relationship between the use of new or used computed tomography (CT) scanners and image retake rates to evaluate the comparative quality of used and new CT scanners.

MATERIAL AND METHODS

This was a retrospective cohort study of patients who first underwent CT from January 1 to June 30, 2008 (n = 258,572). Data were obtained by linking the Health Care Institution Registration Data with the Korean National Health Insurance Claims Database. Image retake rates within 30, 60, 90, and 180 days after the first CT scan were calculated, and differences in the image retake rate by new versus used CT scanners were assessed.

RESULTS

After adjusting for confounders, use of a used CT scanner for the first scan increased the odds of retake within 30 days (odds ratio [OR]: 1.34, 95% confidence interval [CI]: 1.22-1.48), 60 days (OR: 1.59, 95% CI: 1.47-1.72), 90 days (OR: 1.48, 95% CI: 1.38-1.59), and 180 days (OR: 1.38, 95% CI: 1.30-1.46) compared with use of a new CT scanner. Such results were evident in scans of the spine, abdomen, chest, and face or skull base.

CONCLUSION

The quality control associated with import of used CT scanners should be improved. Moreover, regular and detailed quality inspections of used CT scanners currently operating in healthcare institutions are necessary.

Finding an alternative diagnosis does not justify increased use of CT-pulmonary angiography

Background

The increased use of computed tomography pulmonary angiography (CTPA) is often justified by finding alternative diagnoses explaining patients’ symptoms. However, this has not been rigorously examined.

Methods

We retrospectively reviewed CTPA done at our center over an eleven year period (2000 – 2010) in patients with suspected pulmonary embolus (PE). We then reviewed in detail the medical records of a representative sample of patients in three index years – 2000, 2005 and 2008. We determined whether CTPA revealed pulmonary pathology other than PE that was not readily identifiable from the patient’s history, physical examination and prior chest X-ray. We also assessed whether the use of pre-test probability guided diagnostic strategy for PE.

Results

A total of 12,640 CTPA were performed at our center from year 2000 to 2010. The number of CTPA performed increased from 84 in 2000 to 2287 in 2010, a 27 fold increase. Only 7.6 percent of all CTPA and 3.2 percent of avoidable CTPAs (low or intermediate pre-test probability and negative D-dimer) revealed previously unknown findings of any clinical significance. When we compared 2008 to 2000 and 2005, more CTPAs were performed in younger patients (mean age (years) for 2000: 67, 2005: 63, and 2008: 60, (p=0.004, one–way ANOVA)). Patients were less acutely ill with fewer risk factors for PE. Assessment of pre-test probability of PE and D-dimer measurement were rarely used to select appropriate patients for CTPA (pre-test probability of PE documented in chart (% total) in year 2000: 4.1%, 2005: 1.6%, 2008: 3.1%).

Conclusions

Our data do not support the argument that increased CTPA use is justified by finding an alternative pulmonary pathology that could explain patients’ symptoms. CTPA is being increasingly used as the first and only test for suspected PE.

Adherence to PIOPED II investigators' recommendations for computed tomography pulmonary angiography

BACKGROUND

Computed tomography (CT) pulmonary angiography use has increased dramatically, raising concerns for patient safety. Adherence to recommendations and guidelines may protect patients. We measured adherence to the recommendations of Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED II) investigators for evaluation of suspected pulmonary embolism and the rate of potential false-positive pulmonary embolism diagnoses when recommendations of PIOPED II investigators were not followed.

METHODS

We used a structured record review to identify 3500 consecutive CT pulmonary angiograms performed to investigate suspected pulmonary embolism in 2 urban emergency departments, calculating the revised Geneva score (RGS) to classify patients as "pulmonary embolism unlikely" (RGS≤10) or "pulmonary embolism likely" (RGS>10). CT pulmonary angiograms were concordant with PIOPED II investigator recommendations if pulmonary embolism was likely or pulmonary embolism was unlikely and a highly sensitive D-dimer test result was positive. We independently reviewed 482 CT pulmonary angiograms to measure the rate of potential false-positive pulmonary embolism diagnoses.

RESULTS

A total of 1592 of 3500 CT pulmonary angiograms (45.5%) followed the recommendations of PIOPED II investigators. The remaining 1908 CT pulmonary angiograms were performed on patients with an RGS≤10 without a D-dimer test (n=1588) or after a negative D-dimer test result (n=320). The overall rate of pulmonary embolism was 9.7%. Potential false-positive diagnoses of pulmonary embolism occurred in 2 of 3 patients with an RGS≤10 and a negative D-dimer test result.

CONCLUSIONS

Nonadherence to recommendations for CT pulmonary angiography is common and exposes patients to increased risks, including potential false-positive diagnoses of pulmonary embolism.

Pulmonary embolism diagnosis and mortality with pulmonary CT angiography versus ventilation-perfusion scintigraphy: evidence of overdiagnosis with CT?

OBJECTIVE

The purposes of this study were to determine whether pulmonary emboli diagnosed with pulmonary CT angiography (CTA) represent a milder disease spectrum than those diagnosed with ventilation-perfusion (V/Q) scintigraphy, to determine the trends in incidence and mortality among patients with the diagnosis of pulmonary embolism from 2000 to 2007, and to correlate incidence and mortality trends with imaging modality trends.

MATERIALS AND METHODS

Diagnoses of pulmonary embolism from 2000 to 2007 at an urban academic medical center were retrospectively identified. Patient data were collected from the hospital database and the Social Security Death Index. Incident diagnoses, type of imaging used, and date of death were documented. Bivariate and multivariate analyses were used to explore the relations between imaging use and the incidence and mortality of pulmonary embolism. Logistic regression analysis was used to estimate the odds of death of pulmonary embolism diagnosed with pulmonary CTA versus V/Q scintigraphy.

RESULTS

The cases of 2087 patients (1361 women, 726 men; mean age, 61.8 years) with pulmonary embolism were identified. From 2000 to 2007 the incidence of pulmonary embolism increased from 0.69 to 0.91 per 100 admissions in strong correlation with increased use of pulmonary CTA. There was no change in mortality, but the case-fatality rate decreased from 5.7% to 3.3%. On average, pulmonary emboli diagnosed with pulmonary CTA were one half as lethal as those diagnosed with V/Q scintigraphy (odds ratio, 0.538; 95% CI, 0.314-0.921).

CONCLUSION

The results of this study are evidence that the shift in imaging from V/Q scintigraphy to pulmonary CTA resulted in increased diagnosis of a less fatal spectrum of pulmonary embolic disease, raising the possibility of overdiagnosis. Outcome-based clinical trials with long-term follow-up would be helpful to further guide management.

Risk-benefit analysis of pulmonary CT angiography in patients with suspected pulmonary embolus

OBJECTIVE

The objective of our study was to estimate the mortality benefit-to-risk ratio of pulmonary CT angiography (CTA) by setting (ambulatory [emergency department or outpatient] or inpatient), age, and sex.

MATERIALS AND METHODS

A retrospective evaluation of 1424 consecutive pulmonary CTA examinations was performed and the following information was recorded: examination setting, patient age, patient sex, pulmonary CTA interpretation for pulmonary embolus (PE), and CT radiation exposure (dose-length product). We estimated mortality benefit of pulmonary CTA by multiplying the rate of positive pulmonary CTA examinations by published estimates of mortality of untreated PE in ambulatory and inpatient settings. We estimated the lifetime attributable risk of cancer mortality due to radiation from pulmonary CTA by calculating the estimated effective dose and using sex-specific polynomial equations derived from the Biological Effects of Ionizing Radiation VII report. We calculated benefit-to-risk ratios by dividing the mortality benefit of preventing a fatal PE by the mortality risk of a radiation-induced cancer.

RESULTS

Pulmonary CTA diagnosed PE in 188 of 1424 patients (13.2%). Both inpatients (101/723, 14.0%) and emergency department patients (74/509, 14.5%) had significantly higher rates of PE than outpatients (13/192 [6.8%]). Males received significantly (p = 0.02451) higher radiation dose (9.7 mSv) than females (8.4 mSv), but males had a significantly (p < 0.0001) lower lifetime attributable risk of cancer mortality than females. Assuming an untreated PE mortality rate of 5% for ambulatory patients and 30% for inpatients, the benefit-to-risk ratio ranged from 25 for ambulatory patients to 187 for inpatients. Ambulatory women had the lowest benefit-to-risk ratio.

CONCLUSION

The benefit-to-risk ratio of pulmonary CTA in patients with suspected PE ranges from 25 to 187 and can be increased by optimizing the radiation dose.

Prospective study of the incidence of contrast-induced nephropathy among patients evaluated for pulmonary embolism by contrast-enhanced computed tomography

OBJECTIVES

Contrast-enhanced computed tomography (CECT) of the pulmonary arteries (CTPA) has become the mainstay to evaluate patients with suspected pulmonary embolism (PE) and is one of the most common CECT imaging studies performed in the emergency department (ED). While contrast-induced nephropathy (CIN) is a known complication, this risk is not well defined in the ED or other ambulatory setting. The aim of this study was to define the risk of CIN following CTPA.

METHODS

The authors enrolled and followed a prospective, consecutive cohort (June 2007 through January 2009) of patients who received intravenous (IV) contrast for CTPA in the ED of a large, academic tertiary care center. Study outcomes included 1) CIN defined as an increase in serum creatinine (sCr) of ≥ 0.5 mg/dL or ≥ 25%, 2 to 7 days following contrast administration; and 2) severe renal failure defined as an increase in sCr to ≥ 3.0 mg/dL or the need for dialysis within 45 days and/or renal failure as a contributing cause of death at 45 days, determined by the consensus of three independent physicians.

RESULTS

A total of 174 patients underwent CTPA, which demonstrated acute PE in 12 (7%, 95% confidence interval [CI] = 3% to 12%). Twenty-five patients developed CIN (14%, 95% CI = 10% to 20%) including one with acute PE. The development of CIN after CTPA significantly increased the risk of the composite outcome of severe renal failure or death from renal failure within 45 days (relative risk = 36, 95% CI = 3 to 384). No severe adverse outcomes were directly attributable to complications of venous thromboembolism (VTE) or its treatment.

CONCLUSIONS

  In this population, CIN was at least as common as the diagnosis of PE after CTPA; the development of CIN was associated with an increased risk of severe renal failure and death within the subsequent 45 days. Clinicians should consider the risk of CIN associated with CTPA and discuss this risk with patients.

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.

Diagnostic accuracy of magnetic resonance imaging for an acute pulmonary embolism: results of the 'IRM-EP' study

BACKGROUND

Magnetic resonance imaging (MRI) has not been validated as an alternative diagnostic test to computed tomography angiography (CTA) in patients with suspicion of a pulmonary embolism (PE).

OBJECTIVES

To evaluate performance of current MRI technology in diagnosing PE, in reference to a 64-detector CTA.

PATIENTS/METHODS

  Prospective investigation including 300 patients with a suspected PE, referred for CTA after assessment of clinical probability and D-dimer testing. MRI protocol included unenhanced, perfusion and angiographic sequences. MRI results were interpreted by two independent readers, to evaluate inter-reader agreement. Sensitivity and specificity were evaluated globally and according to PE location and to clinical probability category.

RESULTS

Of 300 enrolled patients, 274 were analyzed and 103 (37.5%) had a PE diagnosed by CTA. For patients with conclusive MRI results (72% for reader 1, 70% for reader 2), sensitivity and specificity were 84.5% (95% confidence interval [CI], 74.9-91.4%) and 99.1% (95% CI, 95.1-100.0%), respectively, for reader 1, and 78.7% (95% CI, 68.2-87.1%) and 100% (95% CI, 96.7-100.0%) for reader 2. After exclusion of inconclusive MRI results for both readers, inter-reader agreement was excellent (kappa value: 0.93, 95% CI: 0.88-0.99). Sensitivity was better for proximal (97.7-100%) than for segmental (68.0-91.7%) and sub-segmental (21.4-33.3%) PE (P < 0.0001). Sensitivity was similar for both readers within each clinical probability category.

CONCLUSIONS

Current MRI technology demonstrates high specificity and high sensitivity for proximal PE, but still limited sensitivity for distal PE and 30% of inconclusive results. Although a positive result can aid in clinical decision making, MRI cannot be used as a stand-alone test to exclude PE.

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.

Performance of the Pulmonary Embolism Rule-out Criteria (the PERC rule) combined with low clinical probability in high prevalence population

INTRODUCTION

PERC rule was created to rule out pulmonary embolism (PE) without further exams, with residual PE risk<2%. Its safety is currently not confirmed in high PE prevalence populations even when combined with low clinical probability assessed by revised Geneva score (RGS). As PERC rule and RGS are 2 similar explicit rules with many redundant criteria, we hypothesized that the combination of PERC rule with gestalt clinical probability could resolve this limitation.

METHODS

We collected prospectively documented clinical gestalt assessments and retrospectively calculated PERC rules and RGS from a prospective study of PE suspected patients. We analyzed performance of combinations of negative PERC with low clinical probability assessed by both methods in high overall PE prevalence population.

RESULTS

Among the final study population (n = 959), the overall PE prevalence was 29.8%. Seventy-four patients (7.7%) were classified as PERC negative and among them, 4 patients (5.4%) had final diagnosis of PE. When negative PERC was combined with low pretest probability assessed by RGS or gestalt assessment, PE prevalence was respectively 6.2% and 0%. This last combination reaches threshold target of 2% and unnecessary exams could easily have been avoided in this subgroup (6%). However, it confidence interval was still wide (0%; CI 0-5).

CONCLUSIONS

PERC rule combined with low gestalt probability seems to identify a group of patients for whom PE could easily be ruled out without additional test. A larger study is needed to confirm this result and to ensure safety.