Computed tomography pulmonary angiogram ordering, adherence to decision rules and yield in the emergency department: An observational study

OBJECTIVE

Pulmonary embolism (PE) frequently requires diagnosis through CT pulmonary angiogram (CTPA). Appropriate application of evidence-based clinical decision tools can reduce unnecessary CTPAs. This study assessed adherence to and the efficacy of various aspects of the Queensland Health suspected PE diagnostic pathway, including Wells score, PE rule out criteria (PERC) and age-adjusted D-dimer interpretation.

METHODS

Retrospective study of CTPAs ordered from 1 January to 30 April 2023 in a tertiary and urban ED in Southeast Queensland. Data on clinical variables, D-dimer and CTPA results were collected through medical record and radiology database review. Descriptive analyses were used to determine adherence to Queensland guidelines and performance of D-dimer interpretation tools (including comparison of age-adjusted PE with a new pre-test probability [PTP]-based model using D-dimer cut-off <1000 ng/mL for Wells score ≤4 and 500 ng/mL for Wells score 4.5-6).

RESULTS

A total of 573 CTPAs were available for analysis with a 12.4% (95% confidence interval 10.0-15.4) diagnostic yield. Stratification by Wells score showed yields of 4.0%, 18.5% and 41% for low-, moderate- and high-risk patients, respectively. Twenty-five patients with low-PTP who received CTPA could have been excluded with the PERC rule. Age-adjusted D-dimer interpretation may have prevented 26 CTPAs with no false negatives, whereas PTP approach may have prevented 128 CTPAs with four false negatives.

CONCLUSION

Guideline adherence can be improved, and adherence to existing clinical decision tools may reduce unnecessary CTPA ordering and increase diagnostic yield. The use of the age-adjusted D-dimer had good sensitivity, whereas the new PTP approach will require further prospective research.

Left atrium volume and ventricular volume ratio algorithm as indication of pulmonary hypertension etiology

BACKGROUND

Pressure overload of the right heart (pulmonary hypertension [PH]) can be an acute or a chronic process with various pathophysiologic changes affecting the dimensions of the heart chambers. The automatic four-chamber volumetric analysis tool is now available to measure the volume of the cardiac chambers in patients undergoing a computed tomography pulmonary angiogram (CTPA).

PURPOSE

To characterize the volumetric changes that occurred in response to increased systolic pulmonary arterial pressures (sPAP) in acute events, such as acute pulmonary embolism (APE), compared with other etiologies.

MATERIAL AND METHODS

Consecutive patients who underwent CTPA and echocardiography within 24 h between 2011 and 2015 were included. Differences in cardiac chamber volumes were investigated in correlation to the patients' sPAP.

RESULTS

The final cohort of 961 patients included 221 (23%) patients diagnosed with APE. The right (RV) to left (LV) ventricular volume ratio (VVR) was higher, while the left atrial (LA) volume index was smaller (P < 0.001) in the patients with APE. A decision tree for the prediction of APE showed that an RV to left VVR >2.8 was characteristic of APE, whereas an LA volume index >37.5 mL/m² was more compatible with PH due to other etiologies (P < 0.001).

CONCLUSION

The combination of VVR and LA volume index may help in differentiating between APE and chronic PH. CTPA-based volumetric information may be used to help clarify the underlying etiology of the dyspnea.

Raising the D-dimer threshold for ruling out pulmonary embolism: A single-site, observational study with a historical comparison

OBJECTIVE

The objective of this study was to assess the impact of introduction of a new pulmonary embolism (PE) diagnostic guideline with a raised D-dimer threshold.

METHODS

This is a single-site, observational, cohort study with a historical comparison. The new guideline raised the D-dimer threshold to 1000 ng/mL for most patients with a Wells' score of 4 or less. Patients investigated for PE with a D-dimer level and/or definitive imaging in 6-month periods before and after the introduction of the guideline were eligible. Patients with D-dimers of 500-1000 ng/mL were prospectively followed up at 3 months for missed PE.

RESULTS

During the pre-intervention period, 688 patients were investigated for PE, 366 (53.2%) received definitive imaging and 39 PE were diagnosed (5.7% overall, 10.7% of those imaged). For the 121 patients with D-dimers ≥500 and <1000 ng/mL, 87 (71.9%) were imaged with 7 (5.8%) having a PE diagnosed. Post intervention there were 930 patients, of which 426 (45.8%) received definitive chest imaging and there were 50 patients with PE diagnosed (5.4% overall, 11.7% of those imaged). For the 185 patients with D-dimers ≥500 and <1000 ng/mL, 60 (32.4%) were imaged with 5 (2.7%) having PE diagnosed. No cases of missed PE were identified at 3 months.

CONCLUSION

The introduction of the new guideline was associated with a reduction in overall imaging rates without evidence of missed PE. Further evaluation in other settings is recommended.

Excluding Pulmonary Embolism with End-tidal Carbon Dioxide: Accuracy, Cost, and Harm Avoidance

A non-randomized single center prospective, descriptive, correlational design was used to determine what end-tidal carbon dioxide (EtCO₂) level provided the best sensitivity, specificity, and negative predictive value to exclude pulmonary embolism (PE) diagnosis in hemodynamically stable hospitalized adults (n = 111). The financial impact and harm avoidance of adding EtCO₂ to the PE diagnostic process also were examined. PE diagnosis was determined by computed tomography pulmonary angiography (CTPA). PE prevalence was 18.9%. Mean±SD EtCO₂ was lower for PE positive than negative participants (28 ± 7.8 to 33 ± 8.1 mmHg respectively 95% CI: 1.22-8.96; P = .01). For PE exclusion, an EtCO₂ cutoff ≥42 mmHg yielded 100% sensitivity, 12.2% specificity, and 100% negative predictive value. For every six inpatients assessed with EtCO₂, one could be saved from unnecessary CTPA. Eliminating unnecessary CTPA removes the potential harm associated with radiation and intravenous contrast exposure. Additionally, an EtCO₂ cutoff ≥42 mmHg could eliminate ~$88,000/year in healthcare waste at this institution.

Age-adjusted cut-off using the IL D-dimer HS assay to exclude pulmonary embolism in patients presenting to emergency

BACKGROUND/AIM

The ADJUST-PE study showed that an age-adjusted D-dimer (AADD) (age years × 10 ng/mL if >50 years) combined with an unlikely pre-test probability (PTP) can increase the proportion of older patients in whom pulmonary embolism (PE) can be safely excluded, but the IL D-dimer HS assay was not assessed. To assess the ability of the IL D-dimer HS assay to exclude PE using the AADD.

METHODS

Retrospective analysis of consecutive patients presenting with symptoms of acute PE to one of three Monash Health Emergency Departments (January 2013-January 2014) who had computed tomography pulmonary angiography. In the group with D-dimer, efficiency (proportion of PE excluded based on a combination of unlikely PTP and negative D-dimer) was determined using (i) current laboratory (200 ng/mL), (ii) conventional (230 ng/mL) and (iii) modified (375 ng/mL if age ≥60 years) AADD cut-offs.

RESULTS

A total of 176 patients with D-dimers was included (mean age = 58.5 years; 54.0% males; 71.0% age >50 years). Prevalence of PE in the overall, unlikely and likely PTP groups, was 17.0, 13.0 and 24.6% respectively. In the unlikely PTP group (115 patients), efficiency for the current, conventional, modified and AADD cut-offs was 9.6, 24.3, 30.4 and 37.4% respectively.

CONCLUSION

The absolute increase in efficiency of an AADD compared to conventional cut-off using the IL D-dimer HS assay is modest (~10%) and requires prospective validation. Modifying our cut-off to 230 ng/mL and systematic implementation of a clinical algorithm, including D-dimer testing and PTP, is likely a more important first step.

Imaging for Pulmonary Embolism in Sickle Cell Disease: A 17-Year Experience

Sickle cell disease, a complex disorder with known pulmonary complications, has the potential to confound the diagnosis of pulmonary embolism. We hypothesized that when the choice of imaging is guided by chest radiographic results, CT pulmonary angiography (CTPA) and ventilation-perfusion (V/Q) scintigraphy have comparable diagnostic performance in sickle cell disease. Methods: A retrospective cohort of adults with sickle cell disease who were imaged for suspected pulmonary embolism with either CTPA or V/Q, from 2000 to 2016 at our institution, was established. To reduce radiation exposure, our practice recommends V/Q for stable patients with normal chest radiographs. Results of index pulmonary embolism imaging, 90-d follow-up, and results of chest radiography were recorded. Results: Two hundred forty-five adults with sickle cell disease comprised the cohort. The mean age (±SD) was 33 ± 10.5 y, and 58% (141) were men. Index imaging was V/Q in 62.9% (n = 154) and CTPA in 37.1% (n = 91). Chest radiographs, performed in 96.3% (n = 236), were normal in 72.9% (n = 172). Imaging results for pulmonary embolism were negative in 88.2% (n = 216), positive in 4.1% (n = 10), and indeterminate in 7.8% (n = 19) with no difference between V/Q and CTPA (P = 0.63). Reimaging within 90 d occurred in 9.8% (n = 24), 14.7% (20/136) after initial V/Q, and 5% (4/109) after initial CTPA (P = 0.08). Reimaging revealed a pulmonary embolism diagnosis after negative/indeterminate results in 0.7% (1/149) of V/Qs and 1.2% of (1/86) CTPAs (P = 0.69). Over the 17-y study period, 47% (114/245) underwent repeated imaging, and 11% (27/245) were diagnosed with pulmonary embolism at least once. Conclusion: In sickle cell disease patients with suspected pulmonary embolism, positive imaging rates were low for any given clinical presentation, but 11% of the cohort was diagnosed with pulmonary embolism over the 17-y study period. CTPA and V/Q performed comparably for pulmonary embolism diagnosis when the choice of imaging was guided by results of chest radiography. Hence, V/Q is a reasonable first choice for sickle cell disease patients with normal chest radiographs.

Predictive value of symptoms, signs and biomarkers on computed tomography pulmonary angiogram results

BACKGROUND

Pulmonary embolism (PE) is associated with significant morbidity and mortality. PE is a heterogeneous entity that causes a wide variety of clinical presentations, making it imperative to establish which clinical symptoms, signs and biomarkers can influence the pretest probability of PE to aid clinicians and reduce over testing.

AIM

To analyse the clinical parameters used by clinicians to order a computed tomography pulmonary angiogram (CTPA) and establish which were associated with the presence of PE.

METHODS

Medical records of patients who underwent CTPA from December 2015 to March 2016 were extracted. Patient demographics, clinical symptoms, diagnostic and radiological results were analysed.

RESULTS

The study included 150 CTPA studies. Of the studies, 25 were positive for PE and 125 were negative. There was no significant relationship between the presence or character of chest pain and a positive CTPA result (P = 0.216). Previous history of venous thromboembolism (VTE) (P < 0.0001), one or more risk factors for VTE and positive troponin (P < 0.002) were all predictive of PE. None of the patients with a negative D-dimer had a positive CTPA.

CONCLUSION

This study supports the negative predictive value of the D-dimer for excluding PE and demonstrates that the strongest pretest predictors of PE in our population are a prior history of VTE, risk factors for VTE and elevated troponin. None of the parameters that often generate requests for CTPA, including vital signs or the presence of chest pain, was associated with the presence of PE in our study population.

Clinical application of the Innovance D-dimer assay in the diagnosis of acute pulmonary thromboembolism

Patients with acute pulmonary thromboembolism (APTE) have a high short-term mortality rate. The current study aimed to investigate the use of D-dimer in the diagnosis of APTE in suspected APTE patients. All suspected APTE patients were classified into diagnosis or control groups according to the results of a computed tomography pulmonary angiogram. Mann-Whitney U and Kruskal-Wallis H tests were used to evaluate the association between D-dimer values and APTE. Area under the curve (AUC) values and the Youden Index were used to determine D-dimer cut-off levels for the prediction of APTE. The data of 112 suspected APTE patients (54.8% women; mean age, 70.5 years) were analyzed prospectively. There were no significant differences in age (74.5 vs. 73.5 years, P=0.538) or gender distribution (female ratio 56.5 vs. 53.0%, P=0.847) between the diagnosis and control groups. The incidence of symptoms including dyspnea (67.4 vs. 33.3%; P<0.01), chest distress (47.8 vs. 25.8%; P<0.05) and elevated D-dimer (8.49 vs. 0.97 mg/l; P<0.001) were significantly higher in patients with APTE compared with the control group. D-dimer values >3.32 mg/l fibrinogen equivalent units (FEU) were indicative of APTE and the Youden Index was 0.69. The maximum AUC was 0.87 (95% CI: 0.79-0.92), the sensitivity and specificity were 89.13 and 80.30%, respectively, the positive and negative likelihood ratios were 4.53 and 0.14, respectively, and the positive and negative predictive values were 75.90 and 91.40%, respectively. A D-dimer value <0.60 mg/l FEU was the optimal threshold for excluding APTE diagnosis, with a sensitivity of 100.0% and a specificity of 28.79%. The positive and negative likelihood ratios were 1.40 and 0.00, respectively, and the positive and negative predictive values were 49.50 and 100.00%, respectively. Thus, D-dimer levels, combined with clinical assessment, yield high sensitivity and specificity in diagnosing APTE.

Pulmonary embolism in Bradford, UK: role of end-tidal CO2 as a screening tool

End-tidal CO2 (ETCO2) can represent dead space ventilation. The authors aimed to define the optimum ETCO2 to conclusively exclude a pulmonary embolic event. One hundred consecutive patients with suspected pulmonary embolisms (PEs) were enrolled over 6 months in 2012. Symptoms, demographic date, Wells' score, D-dimer levels and the gold standard computed tomography pulmonary angiogram (CTPA) results were collated for analysis. ETCO2 was measured within 24 hours of presentation in all 100 patients. Patient ages ranged from 18 years to 93 years. PE was diagnosed in 38% of cases. The average ETCO2 in patients with a positive CTPA was 3.35 kPa (range 2.4-4.2 kPa, SD 0.50). The average ETCO2 in patients without a PE was 4.41 kPa (range 1.3-6.6 kPa, SD 1.10). All patients positive for a PE obtained an ETCO2 <4.3 kPa (32.3 mmHg). This point (4.3 kPa) had a sensitivity and specificity (100% and 68% respectively), with a negative predictive value of 100% and positive predictive value of 66%. ETCO2 may reliably be used to screen and exclude patients with suspected PEs. If used in combination with D-dimer with clinical probability as a screening tool, CTPA will be required in only a minority of patients.

Diagnostic yield and renal complications after computed tomography pulmonary angiograms performed in a community-based academic hospital

Background

Venous thromboembolism and pulmonary embolism (VTE/PE) remain a diagnostic challenge. The computed tomography pulmonary angiogram (CTPA) has emerged as a popular diagnostic test for PE. However, there is limited data on diagnostic yield and complications in actual clinical settings. Our goal was to determine the diagnostic yield for PE and rate of renal complications following CTPA in a large community hospital setting.

Methods

A retrospective chart review of 1,514 patients who underwent CTPA in the emergency department or during the initial 24 hours of admission to a community-based academic hospital.

Results

Of 1,514 CTPAs, 125 were positive for VTE/PE yielding a positive diagnosis in 8.2%. Dyspnea was the most common symptom in patients and a normal physical exam was the most common finding. Among the 925 patients with adequate data to calculate the rate of contrast-induced nephropathy (CIN), 25.8% had an increase of at least 25% in serum creatinine following the CTPA. Pre-existing diabetes and age were the most important predictors of CIN.

Conclusions

CTPA has a low diagnostic yield for PE in a community setting, and in some patient populations, the rate of contrast-induced nephropathy may be higher than previously reported in the literature. Due to the retrospective nature of this study we were limited in using pre-test scoring systems and in measuring the impact of alternative CT diagnoses on patient management.