Low Probability Of Pulmonary Embolism Research Articles

Clinicians' interpretation of ventilation/perfusion lung scan reports: Where are we today?

Clinicians' interpretation of lung scan reports will determine which further management decisions are taken when potentially fatal pulmonary embolism (PE) is suspected. To assess current referring clinicians' interpretation of the terminology used in ventilation/perfusion (V/Q) scan reports, whether this interpretation is affected by experience level, and how it affects clinical management decisions. This was a questionnaire-based cross-sectional study. Between September 2020 and May 2021, 300 questionnaires were distributed among clinicians who refer patients for V/Q scans. Of the 162 clinicians who responded, 94% thought that there is >85% likelihood of PE or definitely PE present when a scan is reported as 'high probability of PE'; 87% interpreted 'low probability of PE' as <10% likelihood of PE or definitely no PE present. Overall, >70% of clinicians across all experience levels correctly interpreted the intended meaning of probability categories according to the Modified Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II criteria. Of the respondents, 77% agreed that clinically significant PE is ruled out by a normal scan. Further investigation for inconclusive findings, features of parenchymal lung disease and cardiomegaly were selected by 72%, 93% and 98% of clinicians, respectively. The findings of this study regarding high-probability scan results were in line with existing literature on lung scan report interpretation. However, our findings regarding low-probability scan results and negative V/Q scan specificity contrasted with the findings in these articles, suggesting that clinicians are now more familiar with lung scan interpretation guidelines. Experience level did not significantly affect interpretation of reports. Although most clinicians agreed that a negative scan excludes clinically significant PE, two-thirds of them would still subject the patient to further unnecessary investigations to exclude PE. What the study adds. Our findings regarding a low-probability ventilation/perfusion (V/Q) scan and the specificity of a negative V/Q scan contrasted with previous articles on lung scan interpretation, suggesting that clinicians are now more familiar with lung scan interpretation guidelines.Implications of the findings. Although most clinicians understood the negative predictive value of a V/Q scan, 20% would still investigate further with computed tomography pulmonary angiography or treat as confirmed pulmonary embolism. Education of clinicians about the negative predictive value of V/Q scans is important to avoid unnecessary radiation or anticoagulation.

CO-Oximetry Interference in a Patient with Dyspnea Refractory to Oxygen Therapy.

A 37-year-old female with a past medical history of renal transplant secondary to nephropathic cystinosis, chronic kidney disease, and Pneumocystis jirovecii pneumonia 7 months prior presented to the emergency department with exertional dyspnea 5 days after initiating dapsone for Pneumocystis jirovecii pneumonia prophylaxis. Vitals and physical exam were significant for tachycardia, peripheral cyanosis, and peripheral functional oxygen saturation via pulse oximetry of 89% with no increase following initiation of 40 L/min of oxygen therapy. Respiratory exam findings were normal, and the patient was afebrile. Initial lab values were significant for anemia with no leukocytosis noted. Portable chest radiograph and chest computed tomography revealed no acute thoracic pathology, and ventilation/perfusion scan revealed a low probability of pulmonary embolism. In-house testing for presumed methemoglobinemia was pursued, and the patient was admitted. Fractional methemoglobin [(F)metHb] was tested with a Radiometer ABL835 FLEX but was unable to be obtained due to an...

Saddle pulmonary embolism on non-contrast CT

Background: A saddle pulmonary embolism (PE) is a large embolism that straddles the bifurcation of the pulmonary trunk. This PE extends into the right and left pulmonary arteries. There is a greater incidence in males. Common features of a PE include dyspnea, tachypnea, cough, hemoptysis, pleuritic chest pain, tachycardia, hypotension, jugular venous distension, and severe cases Kussmaul sign. The Wells criteria for PE is used as the pretest probability. Diagnostics include D-dimer levels, CT pulmonary angiography (CTPA), ventilation/perfusion scintigraphy (V/Q scan), echocardiography, lower extremity venous ultrasound, chest x-ray, pulmonary angiography, and electrocardiography (ECG). Case description: We present a 65-year-old male that presented with a two-week history of dyspnea with non-radiating intermittent chest pressure. Initial V/Q scan showed a low probability for PE, but a subsequent non-contrast CT revealed that he indeed had a saddle PE.

Derivation and Validation of a 4-Level Clinical Pretest Probability Score for Suspected Pulmonary Embolism to Safely Decrease Imaging Testing

In patients with suspected pulmonary embolism (PE), overuse of diagnostic imaging is an important point of concern. To derive and validate a 4-level pretest probability rule (4-Level Pulmonary Embolism Clinical Probability Score [4PEPS]) that makes it possible to rule out PE solely on clinical criteria and optimized D-dimer measurement to safely decrease imaging testing for suspected PE. This study included consecutive outpatients suspected of having PE from US and European emergency departments. Individual data from 3 merged management studies (n = 11 114; overall prevalence of PE, 11%) were used for the derivation cohort and internal validation cohort. The external validation cohorts were taken from 2 independent studies, the first with a high PE prevalence (n = 1548; prevalence, 21.5%) and the second with a moderate PE prevalence (n = 1669; prevalence, 11.7%). A prior definition of pretest probability target values to achieve a posttest probability less than 2% was used on the basis of the negative likelihood ratios of D-dimer. Data were collected from January 2003 to April 2016, and data were analyzed from June 2018 to August 2019. The rate of PE diagnosed during the initial workup or during follow-up and the rate of imaging testing. Of the 5588 patients in the derivation cohort, 3441 (61.8%) were female, and the mean (SD) age was 52 (18.5) years. The 4PEPS comprises 13 clinical variables scored from -2 to 5. It results in the following strategy: (1) very low probability of PE if 4PEPS is less than 0: PE ruled out without testing; (2) low probability of PE if 4PEPS is 0 to 5: PE ruled out if D-dimer level is less than 1.0 μg/mL; (3) moderate probability of PE if 4PEPS is 6 to 12: PE ruled out if D-dimer level is less than the age-adjusted cutoff value; (4) high probability of PE if 4PEPS is greater than 12: PE ruled out by imaging without preceding D-dimer test. In the first and the second external validation cohorts, the area under the receiver operator characteristic curves were 0.79 (95% CI, 0.76 to 0.82) and 0.78 (95% CI, 0.74 to 0.81), respectively. The false-negative testing rates if the 4PEPS strategy had been applied were 0.71% (95% CI, 0.37 to 1.23) and 0.89% (95% CI, 0.53 to 1.49), respectively. The absolute reductions in imaging testing were -22% (95% CI, -26 to -19) and -19% (95% CI, -22 to -16) in the first and second external validation cohorts, respectively. The 4PEPS strategy compared favorably with all recent strategies in terms of imaging testing. The 4PEPS strategy may lead to a substantial and safe reduction in imaging testing for patients with suspected PE. It should now be tested in a formal outcome study.

Age-Adjusted D-Dimer in the Prediction of Pulmonary Embolism: Systematic Review and Meta-analysis.

Background:Pulmonary embolism (PE), depending on the severity, carries a high mortality and morbidity. Proper evaluation, especially in patients with low probability for PE, is important to avoid unnecessary diagnostic testing.Objective:To review the diagnostic utility of conventional versus age-adjusted D-dimer cutoff values in patients 50 years and older with suspected pulmonary embolism.Methods:Systematic review with univariant and bivariant meta-analysis.Data sources:We searched PubMed, MEDLINE, and EBSCO for studies published before September 20th, 2020. We cross checked the reference list of relevant studies that compares conventional versus age-adjusted D-dimer cutoff values in patients with suspected pulmonary embolism.Study selection:We included primary published studies that compared both conventional (500 µg/L) and age-adjusted (age × 10 µg/L) cutoff values in patients with non-high clinical probability for pulmonary embolism.Results:Nine cohorts that included 47 720 patients with non-high clinical probability were included in the meta-analysis. Both Age-adjusted D-dimer and conventional D-dimer have high sensitivity. However, conventional D-dimer has higher false positive rate than age-adjusted D-dimer.Conclusion:Age-adjusted D-dimer cutoffs combined with low risk clinical probability assessment ruled out PE diagnosis in suspected patients with a decreased rate of false positive tests.

D-dimer value in the diagnosis of pulmonary embolism-may it exclude only?

Pulmonary embolism (PE) is the third most common cause of death for cardiovascular diseases in Europe. Quick PE diagnosis is therefore crucial for prognosis improvement. It is critical to have suitable screening tests both to exclude PE as well to select patient with highest likelihood of PE occurrence. Currently D-dimer test is accepted as important tool useful to exclude PE in low risk patients. Our goal was to assess the D-dimer test positive prognostic value. A retrospective study based on medical record analysis of consecutively admitted patients to 9 wards of The University Clinical Center in Katowice who were hospitalized during four consecutive years was performed. Three hundred and seventy patients met the inclusion criteria for the study, which involved the D-dimer tests and computed tomographic pulmonary angiography (CTPA) performed during hospitalization. Assessed patients were divided into two groups: PE confirmed and PE excluded by CTPA. We have found that patients with D-dimer levels higher than 2,152 ng/mL had significantly increased risk of PE [area under curve (AUC) of 0.69; 95% CI, 0.64-0.75; P<0.05]. Positive predictive value (PPV) reached the level of 53%, whereas negative predictive value (NPV) reached 82%. We also found that patients with the history of neoplasm and at >65 years of age had D-dimer cut-off point moved to the level of 2,652 ng/mL (AUC of 0.67; 95% CI, 0.52-0.81; P<0.05). Whereas the NPV of the D-dimer test is generally accepted our results suggest that, in selected cases, an increased plasmatic D-dimer levels may have PPV in PE diagnosis. Patients with the history of neoplasm have higher cut-off D-dimer points above which we should consider increased PE likelihood. CTPA should be considered even for patients with low probability of PE when D-dimer values exceed four times the normal level.

Computed tomography pulmonary angiography is overused to diagnose pulmonary embolism in the emergency department of academic community hospital

ABSTRACTBackground: Pulmonary embolism (PE) is a common disease in the USA responsible for up to 10% of hospital mortality. Modified wells score (MWS) and D-dimer assay are used to categorize patients into high or low probability of PE. Patient with high probability need Computed tomography pulmonary angiography (CTPA), while patients with low probability and low D-dimer can safely forgo the CTPA. Objectives: The aim of this study was to investigate the rate of inappropriate CTPA use in the emergency department of a community teaching hospital. Methods: A retrospective chart review of adult patients who underwent CTPA for suspected PE in the emergency department for 2015 was done. CTPA use was considered inappropriate if MWS was less than or equal to 4 and D-dimer was either not ordered or its value was less than 500 μg/L. Bivariate analysis with Fisher’s exact tests and Student’s t-tests as well as multivariate logistic regression analysis were done to examine relationship between study explanatory variables and study outcome.Results: 295 patients were included in the study. The mean age was 51.2(±14.5) years, 68.8% were females. The prevalence of PE was 5.4% and 41% of the CTPAs -were inappropriately ordered. Males were twice (OR 2.1; 95% CI 1.2, 3.6) as likely as females to have an inappropriately ordered CTPA after controlling for a high MWS, age, and tobacco history.Conclusion: CTPA is overused to diagnose PE in the emergency department. Quality improvement projects are needed to encourage physicians to adhere to the current guidelines.

Is stand‐alone D‐dimer testing safe to rule out acute pulmonary embolism?

Background Recently, stand-alone D-dimer testing at a positivity threshold of 750 μg L-1 has been proposed as a safe and efficient approach to rule out acute pulmonary embolism (PE), without additional imaging, but this approach needs validation. Objectives To evaluate stand-alone D-dimer testing at a positivity threshold of 750 μg L-1 to rule out PE. Methods Individual data from 7268 patients with suspected PE previously enrolled in six prospective management studies were used. Patients were assessed by the Wells rule followed by quantitative D-dimer testing in those with a 'PE unlikely' score. Patients were classified post hoc as having a negative (< 750 μg L-1 ) or positive (≥ 750 μg L-1 ) D-dimer. Using a one-stage meta-analytic approach, the negative predictive value (NPV) of stand-alone D-dimer testing was evaluated overall and in different risk subgroups. Results The pooled incidence of PE was 23% (range, 13-42%). Overall, 44% of patients had a D-dimer < 750 μg L-1 , of whom 2.8% were diagnosed with PE at baseline or during 3-month follow-up (NPV, 97.2%; 95% confidence interval [CI], 94.9-98.5). The NPV was highest in patients with a low probability of PE according to the Wells rule (99.2%; 95% CI, 98.6-99.5%) and lowest in those with a high probability of PE (79.3%; 95% CI, 53.0-92.8%). The NPVs in patients with active cancer, patients with previous venous thromboembolism and inpatients were 96.2% (95% CI, 85.6-99.1%), 94.7% (95% CI, 88.6-97.6%) and 92.7% (95% CI, 79.3-97.7%), respectively. Conclusions Our findings suggest that stand-alone D-dimer testing at a positivity threshold of 750 μg L-1 is not safe to rule out acute PE.

Diagnostic prediction models for suspected pulmonary embolism: systematic review and independent external validation in primary care

Objective To validate all diagnostic prediction models for ruling out pulmonary embolism that are easily applicable in primary care.Design Systematic review followed by independent external validation study to assess transportability...

The brain of STEMI

An 83 y/o African Americanmale with a history of hypertension and chronic kidney disease presented following a fall. The fall occurred while he was trying to get up from a sitting position. The patient said he was light-headed and his knees gave way, but at the time of history taking he was asymptomatic. He said he remembered the fall and did not lose consciousness. On presentation his vitals were normal. There were no signs of significant trauma or focal neurological deficits. His initial electrocardiogram (EKG) demonstrated sinus rhythm, rate of 89 beats/min, prolonged QT interval, diffuse arrowhead T wave inversions, and minimal ST segment elevation in lead V1-3 which was alarming for ST segment elevation myocardial infarction (STEMI) (Fig. 1). On laboratory data D dimer was 0.78 mg/dl (normal 0.19– 0.49mg/dl), creatinine 2.3 mg/dl, and first troponin 0.67mg/dl (normal b0.045 mg/dl). Transthoracic 2-dimensional echocardiogram (TTE) showed normal left ventricular systolic function with grade 1 diastolic dysfunction and no regional wall motion abnormality. Ventilation perfusion scan was low probability for pulmonary embolism.

Incidental findings on computed tomography angiography in patients evaluated for pulmonary embolism.

To investigate how often computed tomography (CT) pulmonary angiography contributes to establishing a diagnosis in patients presenting to the emergency department and how it performs compared to chest radiograph. The objective of this study was to measure the ability to identify a diagnosis and to investigate the prevalence and significance of incidental findings in patients evaluated with computed tomography pulmonary angiography in the emergency department. All adult patients evaluated with CT angiography over a 2-year period (January 1, 2011 to December 31, 2012) were included in the analysis. A total of 641 records were identified. Chest radiographs and CT angiography reports were reviewed to determine whether they could provide a diagnosis in patients without pulmonary embolism (PE). Studies negative for PE were stratified into three categories according to significance: type I prompted immediate action, type II required follow up, and type III had findings of limited significance. CT angiography identified a diagnosis in 22.46% of the patient population and in 14.31% of patients without PE. In patients who had CT angiography with chest radiograph, diagnoses were provided in 14.01 and 9.86% of patients, respectively. When analysis was isolated to patients with low probability for PE, CT angiography provided a diagnosis in 20% and chest radiography in 10.23% of patients. The majority of missed cases represented infiltrates too small to be detected by radiography and were believed to represent lung infections by the interpreting radiologist. Among studies negative for PE, 15% were type I, 17.07% were type II, 48.1% were type III, and the rest were normal. CT angiography is superior to chest radiography at providing a diagnosis in patients investigated for PE, even when no PE is present. However, in patients at low risk for PE, the clinical benefit of the additional diagnoses is questionable.

Ventilation/perfusion tomography – V/P-SPECT vs planar technique

Pulmonary embolism (PE) can only be diagnosed with imaging techniques, which in practice is performed using ventilation/perfusion scintigraphy(V/P scintigraphy) or multi-detector computed tomography of the pulmonary arteries (MDCT). The basic principle for the diagnosis of PE based upon V/P scintigraphy is to recognize lung segments or subsegments without perfusion but preserved ventilation, i. e. mismatch. Ventilation/ perfusion single photon emission tomography - V/P SPECT has during the last 10 years started to replace V/P planar based on higher sensitivity, specificity and low non-diagnostic findings. A twenty seven year old woman was suspected for PE when presented to the out-patient clinic due to dyspnea, frequent yawing, oppression in the throat, 3 days after being treated of superficial varices cruris with foam sclerotherapy - UGFS. She was first examined with chest x-ray, MDCT, hearth ultrasonography and V/P planar. V/P planar was reported as very low probability for PE. All the other initial examinations were normal. Patient symptoms did not decline, and reffering clinitian put her on therapy with LMWH. Fifth days later reffering doctor recomended V/P SPECT. V/P SPECT has shown billateral PE, with the cca 35% extent of PE. Patient was followed up clinically and with V/P SPECT one month later. The control V/P SPECT was normal. This case presented importance of high clinical probability and value of V/P SPECT over another imaging technique for detection of PE.

A Rare Case of Acute Respiratory Distress Syndrome Secondary to Acute Lithium Intoxication

Lithium carbonate is a widely administered antimanic drug used for the treatment of bipolar disorder, schizoaffective disorder, and depression. Despite the established clinical efficacy of lithium, its usage must be approached with caution due to its narrow therapeutic index. Lithium poisoning results in multisystem toxicity, and characteristic clinical manifestations are directly correlated to serum lithium concentration. We describe a rather rare but fatal side effect of lithium: acute respiratory distress syndrome (ARDS) in a 46-year-old female on lithium for the treatment of bipolar disease. She was referred for generalized weakness, found in hemodynamic compromise, and had laboratory data significant for a lithium level of 3.3 mmole/L, needing emergent hemodialysis. Subsequently, she developed hypoxic respiratory failure requiring intubation. Her chest x-rays showed new bilateral pulmonary edema, the computed tomography scan showed extensive alveolar consolidation and V/Q scan of low probability for pulmonary embolism. She underwent 3 dialysis sessions and supportive care and was able to be extubated in 5 days. To our knowledge, 4 cases of ARDS after the onset of lithium toxicity have been documented. All patients presented with altered mental status at serum lithium levels ranging from 3.8 to 4.9 mmole/L and cardiogenic etiologies in addition to other likely causes of ARDS were ruled out in each case. The patients were treated with saline hydration (50%) or hemodialysis (50%), indicating that hemodialysis may be a permissive factor in lithium-associated ARDS development rather than a required component. Taken together, we believe that lithium is a likely culprit in the initiation of ARDS and propose the addition of ARDS to the family of clinical manifestations of severe lithium toxicity.

Cardiac Tamponade in a Patient Treated with Infliximab for Crohnʼs

Purpose: Introduction: Anti-tumor necrosis factor-alpha agents are commonly used in the treatment of Crohn's disease. But treatment may be complicated by adverse reactions. We report a rare case of cardiac tamponade in a patient with Crohn's disease who was started on infliximab. Case Report: A 79-year-old man was admitted to the intensive care unit with chest pain and dizziness. On arrival, he was hypotensive with a blood pressure of 80/50 mmHg. Dopamine and dobutamine were started for presumed cardiogenic shock. On examination, he was sweaty and clammy. Heart sounds were distant and chest was clear to auscultation. His past history was significant for Crohn's disease affecting the colon and distal ileum and coronary artery disease. He was on aspirin, clopidogrel, atorvastatin, 5-amino salicylic acid (Asacol), and most recently infliximab. He had received two doses at 5 mg/kg. A chest x-ray revealed subtle cardiomegaly. A V/Q scan showed a low probability of pulmonary embolism. His echocardiogram showed moderate pericardial effusion. Cardiac catheterization revealed a diastolic equalization of pressures on catheterization at 17 mm Hg which indicated cardiac tamponade and prompted urgent pericardiocentesis. 450 ml of blood stained fluid was removed. Patient's symptoms and the need for ionotropic support immediately resolved. Pericardial fluid analysis showed inflammatory picture. Fluid gram stain and culture were negative. ANA and anti-dsDNA were negative. The patient was never rechallenged with infliximab in view of the severity of the presumed reaction. Discussion: Pericardial effusions and pericarditis have been reported in patients with rheumatoid arthritis and Crohn's disease treated with anti-TNF-alpha agents. Recurrent pericarditis has been reported in a patient with multiple sclerosis treated with natalizumab. Infective pericarditis may also develop in patients on anti-TNFalpha therapy. In conclusion, we report a rare case of cardiac tamponade in a patient with Crohn's disease treated with infliximab. This serious complication highlights an uncommon reaction to anti-TNF-alpha therapy and emphasizes the need to be vigilant for adverse events.Figure: Pericardial effusion on echocardiogram.

Prognostic value of the Geneva prediction rule in patients in whom pulmonary embolism is ruled out

The prognosis of patients in whom pulmonary embolism (PE) is suspected but ruled out is poorly understood. We evaluated whether the initial assessment of clinical probability of PE could help to predict the prognosis for these patients. Retrospective analysis of data obtained during a prospective multicentre management study. Six general and teaching hospitals in Belgium, France and Switzerland. In 1334 patients in whom PE was ruled out, 3-month mortality data were available (hospital readmission status was unknown for three patients) and clinical probability was evaluated with the revised Geneva score (RGS). Three-month mortality and readmission rates. Three-month mortality and readmissions rates were 3% and 19%, respectively and differed significantly depending on the RGS-determined PE probability group (P<0.001). When compared with patients presenting with a low probability, the risk of death after 3 months was higher in cases of intermediate or high RGS-based probability {odds ratio: 8.7 [95% confidence interval (CI): 2.7-28.5] and 22.6 (95%CI: 2.1-241.2), respectively}. The readmission risk increased with PE probability group (P<0.001). The main causes of death were cancer, respiratory failure and cardiovascular failure. In total, 86% of patients with low RGS-based probability were alive and had not been readmitted to hospital, whereas other patients had a twofold increased risk of death or readmission during the 3-month follow-up. The simplified Geneva score, calculated a posteriori, gave similar results. Initial assessment of clinical probability may help to stratify prognosis of patients in whom PE has been ruled out. Patients with a low probability of PE have a good prognosis. Whether patients with higher probability might benefit from more vigilant care should be evaluated.

CT Angiography in the Evaluation of Acute Pulmonary Embolus

The purpose of this study was to assess the appropriate use of CT angiography (CTA) in the diagnostic evaluation of acute pulmonary embolism (PE). We reviewed a total of 575 CT angiograms obtained to evaluate for PE at a large level 1 trauma teaching hospital from January 2004 through March 2005. Various clinical settings were used for 267 inpatient (46%), 258 emergency department (45%), and 50 outpatient (9%) studies. We excluded CTA performed for other reasons, repeated CTA, and patient records with incomplete clinical data. On the basis of chart review in which the investigators were blinded to final diagnoses, pretest probability of PE according to the Wells criteria was retrospectively assigned to each patient. D-dimer values, when obtained, also were reviewed. The diagnosis of PE was based on final CTA reports. PE was diagnosed in 9.57% of 575 patients. Positivity rates by location were 32 (12%) of the 267 inpatients, 22 (8.5%) of the 258 emergency department patients, and one (2.0%) of the 50 outpatients. Three (< 1%) of the 575 patients had high probability of PE, even though 351 patients had gone directly to CTA. Of the other 572 patients, 158 (28%) had intermediate and 414 (72%) low probability of PE. In the high, intermediate, and low probability groups, two (67%), 24 (15%), and 29 (7%), respectively, of the patients had PE. A D-dimer assay was performed for 224 (39%) of the 575 patients. Thirty-nine (17%) of the 224 patients had normal results (< 0.5 microg/mL); 107 (48%), intermediate results (0.6-2.0 microg/mL); and 78 (35%), abnormal results (> 2.0 microg/mL). In the emergency department cohort, 151 (59%) of 258 patients underwent a D-dimer assay. Thirty-two (21%) of the 151 patients had normal results; 81 (54%), intermediate results; and 38 (25%), abnormal results. Only one patient with a normal D-dimer level and three patients with intermediate D-dimer levels had PE, the equivalent of 3% of each group. The number of CTA examinations ordered for patients with normal and intermediate D-dimer results was 146 (25% of the 575 total studies). Twenty-two (8%) of the 258 emergency department patients had PE, and clinical suspicion of PE was high for 11 (50%), intermediate for 10 (45%), and low for one (5%) of those patients. Our data showed suboptimal use of the Wells criteria and subjective overestimation of the probability of PE before ordering of CTA. Although a definitive acceptable PE positivity rate for CTA has not been established, the 10% yield represents overuse of CTA as a screening rather than a diagnostic examination.

Acute Pulmonary Embolism: Sensitivity and Specificity of Ventilation-Perfusion Scintigraphy in PIOPED II Study

To use Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II data to retrospectively determine sensitivity and specificity of ventilation-perfusion (V/Q) scintigraphic studies categorized as pulmonary embolism (PE) present or PE absent and the proportion of patients for whom these categories applied. The PIOPED II study had institutional review board approval at all participating centers. Patient informed consent was obtained; the study was HIPAA compliant. Approval and consent included those for future retrospective research. Patients in the PIOPED II database of clinical and imaging results were included if they had diagnosis at computed tomographic (CT) angiography, Wells score, and diagnosis at V/Q scanning. V/Q scan central readings were recategorized as PE present (PIOPED II reading = high probability of PE), PE absent (PIOPED II reading = very low probability of PE or normal), or nondiagnostic (PIOPED II reading = low or intermediate probability of PE). A composite reference standard was used: the PIOPED II digital subtraction angiographic (DSA) result, or if there was no definitive DSA result, CT angiographic results that were concordant with the Wells score (ie, positive CT angiographic result and Wells score > 2 or negative CT angiographic result and Wells score < 6). Sensitivity and specificity of recategorized central readings were computed. With the exclusion of patients with intermediate or low probability, the sensitivity of a high probability (PE present) scan finding was 77.4% (95% confidence interval [CI]: 69.7%, 85.0%), while the specificity of very low probability or normal (PE absent) scan finding was 97.7% (95% CI: 96.4%, 98.9%). The percentage of patients with a PE present or PE absent scan finding was 73.5% (95% CI: 70.7%, 76.4%). In a population similar to that in PIOPED II, results of V/Q scintigraphy can be diagnostically definitive in a majority of patients; thus, it can be considered an appropriate pulmonary imaging procedure in patients for whom CT angiography may be disadvantageous.

Managing suspected venous thromboembolism in a mixed primary and secondary care setting using standard clinical assessment and D-dimer in a noninvasive diagnostic strategy

Venous thromboembolism is a potentially lethal disease if not properly treated. Noninvasive strategies have become an attractive clinical option for effective diagnosis. There has been controversy, however, regarding the use of standard clinical rules in a primary care setting. The objective of the present study was to validate a noninvasive diagnostic strategy in an emergency unit giving assistance to patients with primary and secondary care needs. A total of 291 outpatients (primary and secondary care needs) with suspected venous thromboembolism attending the emergency unit of a general hospital from August 2002 to 2004 were retrospectively evaluated. The diagnostic strategy included assessment of risk for venous thromboembolism and a rapid quantitative enzyme-linked immunosorbent assay D-dimer test. Venous thromboembolism was ruled out in patients with a low-probability or intermediate-probability risk (or an unlikely diagnosis) and a negative D-dimer. The prevalence of venous thromboembolism was 8.2%. Patients with an unlikely diagnosis comprised 93.8% of the evaluations for deep venous thrombosis, and those with a low probability for pulmonary embolism comprised 81.4%. Proportions of patients with venous thromboembolic events observed were 7.2% in patients with an unlikely diagnosis of deep venous thrombosis and 3.0% in those with low probability for pulmonary embolism. The percentage of patients with a thrombotic event excluded using this strategy was 37% (positive predictive value 13%, negative predictive value 100%). In conclusion, this noninvasive clinical strategy is safe for ruling out venous thromboembolism, and excludes the need for imaging tests in about one-third of the patients in the population studied.

An Evaluation of d-Dimer in the Diagnosis of Pulmonary Embolism

It may be safe to omit additional diagnostic testing in selected patients with suspected pulmonary embolism (PE) who have a negative D-dimer test, but this approach has never been evaluated in a randomized, controlled trial. To determine if additional diagnostic testing can be safely withheld in patients with suspected PE who have negative erythrocyte agglutination D-dimer test results. Randomized comparisons in 2 subgroups of a prospective multicenter study. 7 university hospitals. 1126 outpatients or inpatients with suspected PE; of these, 456 patients with negative erythrocyte agglutination D-dimer test results were randomly assigned to the intervention groups. Patients were classified into 2 clinical probability groups: those with a low clinical probability of PE (low-probability group) and those with a moderate or high clinical probability of PE, a nondiagnostic ventilation-perfusion lung scan, and no evidence of proximal deep venous thrombosis on bilateral ultrasonography (moderate- or high-probability group). The experimental intervention for both probability groups was no further diagnostic testing for PE. The control intervention for the low-probability group was a ventilation-perfusion lung scan followed by ultrasonography of the proximal deep veins of the legs on the same day. If the lung scan was nondiagnostic, ultrasonography of the legs was repeated 7 and 14 days later. The control intervention for the moderate- or high-probability group was ultrasonography of the proximal deep veins of the legs after 7 and 14 days. In the control and experimental groups, anticoagulation was withheld or withdrawn if PE was not diagnosed. Symptomatic venous thromboembolism (VTE) during 6 months of follow-up. Prevalence of VTE was 15.2% in the 1126 enrolled patients. In the low-probability group, VTE occurred during follow-up in 0 of 182 patients who had no additional diagnostic testing and in 1 of 185 patients who had additional testing (difference, -0.5 percentage point [95% CI, -3.0 to 1.6 percentage points]). In the moderate- or high-probability group, VTE occurred during follow-up in 1 of 41 patients who had no additional diagnostic testing and in 0 of 41 patients who had additional testing (difference, 2.4 percentage points [CI, -6.4 to 12.6 percentage points]). The authors could not enroll 2000 patients as originally planned; 3 randomly assigned patients did not receive the allocated intervention, and 7 received inadequate follow-up. Personnel who performed follow-up evaluations were not blinded to the results of diagnostic testing at enrollment or to allocation group assignments. In patients with a low probability of PE who have negative D-dimer results, additional diagnostic testing can be withheld without increasing the frequency of VTE during follow-up. Low clinical probability and negative D-dimer results occur in 50% of outpatients and in 20% of inpatients with suspected PE.

Diagnosis of pulmonary embolism: A cost-effectiveness analysis

Pulmonary embolism is a major cause of maternal death. The work up for suspected pulmonary embolism is complex, with many potential diagnostic options. We performed a cost analysis to evaluate which of several diagnostic strategies was the most cost-effective with the least number of deaths from pulmonary embolism. We created a decision tree to evaluate the following strategies: (1) Compression ultrasonography followed by anticoagulation (if there is a positive result) or secondary tests, ventilation perfusion scans or spiral computed tomography (if there is a negative result); high probability ventilation perfusion scans (a positive test result) resulted in anticoagulation; low probability ventilation perfusion scans (a negative test) resulted in no treatment; intermediate tests that resulted in a second test (computed tomography or pulmonary angiography). (2) Ventilation perfusion scans as a primary test followed by anticoagulation. (3) Computed tomography followed by anticoagulation (if there is a positive result). The following assumptions were made: The incidence of pulmonary embolism in pregnant women with suspected pulmonary embolism is 5%; 40% of documented pulmonary embolisms have a positive compression ultrasound result; 10% of ventilation perfusion scans for suspected pulmonary embolism are high probability, 60% are indeterminate, and 30% are low probability for pulmonary embolism; the sensitivity of computed tomography is 95%; the sensitivity of angiography is 98%. The assumed mortality rate of treated pulmonary embolism is 0.7% and of untreated pulmonary embolism in pregnancy is 15% (range, 10%-50%). The angiography-associated mortality rate is 0.5%, and the anticoagulation associated mortality rate is 0.2%. The following costs were used for the model: compression ultrasonography, 200.00 dollars; ventilation perfusion scans, 400.00 dollars; angiography, 1000.00 dollars; computed tomography, 500.00 dollars; and anticoagulation, 5982.00 dollars. With baseline assumptions, spiral computed tomography as the initial diagnostic regimen was found to be the most cost-effective at 17,208 dollars per life saved. Sensitivity analyses were performed over a wide range of assumptions that included alteration of the probability of pulmonary embolism, the sensitivity of computed tomography, ventilation perfusion scans, and compression ultrasonography, the cost of computed tomography, and the mortality rate of untreated pulmonary embolism. Our findings remained robust over a wide range of assumptions. Suspected pulmonary embolism remains a diagnostic quandary. Our analysis indicated that spiral computed tomography offers the most cost-effective method for diagnosing this potentially fatal condition.