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Three Part Question

[In adult patients presenting with clinical suspicion of pulmonary embolus] is [noninvasive, multi-organ point of care ultrasound, when compared to CTPA] specific and sensitive enough [to confirm or refute the presence of pulmonary embolus]?

Clinical Scenario

A 24-year-old woman presents to the ED with shortness of breath and pleurisy. She is otherwise healthy and on no medications except the birth control pill for the past year. There are no other clinical signs or symptoms suggestive of DVT, and her heart rate is normal. You wonder whether as an emergency room physician with some training in bedside ultrasound, reliably confirm or refute the diagnosis of a pulmonary embolus using point-of-care ultrasound (POCUS)?

Search Strategy

Pubmed was used for papers of any date to the present (January 2017) – all databases searched.

Google Scholar was used to search for any publications that may have been missed in pubmed.

Pubmed Search: (((((("computed tomography angiography"[MeSH Terms]) OR CT[Text Word])) OR ((((CTPE[Text Word]) OR CTPA[Text Word]) OR CT pulmonary angiogram[Text Word]) OR CT pulmonary embolism[Text Word]))) AND (((("echocardiography"[MeSH Major Topic]) OR ultrasound[Text Word]) OR echo[Text Word]) OR echocardiography[Text Word])) AND (((pulmonary embol*[Text Word]) OR "pulmonary embolism"[MeSH Terms]) OR PE[Text Word])

Google Scholar: Searched for the first 100 results using the terms "ultrasound", "pulmonary embolism”, and "diagnosis”

Search Outcome

614 papers were found on the pubmed search, of which 3 looked specifically at bedside POCUS administered by non-radiologists or technicians. The reference investigation for all 3 papers was always CTPA, and criteria for patient enrollment was also based on Wells criteria calculations and/or d-dimer values. The remaining papers were excluded because of the following reasons:
1. Ultrasound administered by technician or radiologist.
2. Trans-esophageal ultrasound was used.
3. Complex calculations of ultrasound findings requiring expertise beyond that of a minimally trained sonographer to interpret data, not making it a feasible tool in the busy environment of an ED.

93,800 results were found on Google Scholar, no additional papers were identified.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Nazerian et al., 2014, Italy	Three hundred and fifty-seven consecutive patients ? 18 years old suspected of having a PE Included: patients had to have a Well’s score of >4 or D-dimer ? to 500 ng/mL with a CTPA ordered Excluded: patients with a Well’s score ?4 or D-dimer <500 ng/mL Performance of multiorgan, bedside ultrasound in detecting the presence of a PE measured as sensitivity and specificity compared with CTPA POCUS was conducted by 9 ERPs with ultrasound experience, as well as 4 residents, 2 ER and 2 IM. Radiologists who read the CTPAs were blinded to POCUS results and vice versa	Multicenter prospective accuracy study	Lung US Echocardiogram Venous ultrasound Multiorgan POCUS	Sensitivity 60.9% (51.1–70.1) Specificity 95.9% (92.7–98) +LR 15 Sensitivity 32.7% (24.1–42.3) Specificiy 90.9% (86.6–94.2) +LR 3.6 Sensitivity 52.7% (43–62.3) Specificity 97.6% [94.8%–99.1%) + LR 21.7 Sensitivity 90% (82.8–94.9) Specificity 86.2% (81.3–90.3) + LR 6.5 If alternative Dx was seen on multiorgan ◊ Spec. 100%(96.7–100], Sens. 42.9% (36.7–49.3), +1.75	All ERPs had at least 2 years of training in ultrasound use, which is not generalisable at this time to the population’s skill level in POCUS Additionally, the finding of a lower specificity for multiorgan POCUS remains poorly explained in the paper, given that specificity had been quite high in individual organ groups
Koenig et al., 2014, USA	Ninety-six patients ?18 years old suspected of having a PE with a CTPA ordered by an attending physician. Excluded: pregnancy and lack of informed consent The aim of this study was to examine whether point-of-care ultrasonography that includes thoracic ultrasonography, goal-directed ECG and lower extremity DVT study might be useful to reduce the need for CTPA in patients with suspected PE Three staff physicians or three fellows with critical care ultrasound training conducted POCUS. Results were blinded to both ultrasonographers as well as radiologists reading the CTPA	Single center observational prospective study	Patients with alternative diagnosis after POCUS. Patients with DVT on POCUS. Patients without alternative diagnosis after POCUS	Fifty-four had ultrasound findings suggestive of another disease process that could explain the symptoms. In all 54 cases, the patient was negative for PE and the CTPA agreed with the alternative diagnosis provided by bedside US Two cases had positive DVT findings and were also found to have PE on CTPA Forty scans did not have an alternative diagnosis after ultrasound. 12 of those were found to have a PE on CTPA	The study used critical care staff and fellows, not specifically ERPs, but still focused on the use of POCUS as a diagnostic modality. Their level of training in POCUS was quite comprehensive as defined by a competence statement on the subject Convenience sample was used (between 08:00 and 18:00 on weekdays) The study failed to break down sensitivity/specificity per modality and is a big weakness in its utility in comparing different ultrasound techniques
Shiver et al., 2010 USA	61 adult patients undergoing CTA for workup ?PE were candidates. 7 had venous thromboembolism 4 ERPs were the sonographers, 2 of which had no formal ultrasound training. Results were blinded to both radiologists and the ERPs. ERP-performed ultrasound (EPPU) of the lower extremities versus CT venography (CTV) in ED patients undergoing workup for pulmonary embolism (PE)	Single center, prospective study	EPPU utility	Sensitivity 86% (42%–99%) Specificity 100% (91%–100%)	The study used, specifically ERPs, however, only compared leg ultrasound as their POCUS test in diagnosing PE. Convenience sample only, candidates were chosen when 1 of 4 ERPs were on shift. Additionally, the ERPs in the study were quite experienced. This is an earlier study, and it appears multiorgan POCUS has only really become a research interest as of 2014

Comment(s)

The diagnosis and evaluation of patients presenting with shortness of breath has always been a challenge in the busy environment of an ED. Numerous evidence-based approaches have been developed over the years to aid the clinician in risk-stratifying patients based on clinical symptoms and history. However, the reference test to diagnose a PE remains CTPA, which holds with it some potential harm to the patient. It is a fair amount of radiation as well as even contraindicated in certain patient populations. Ultrasound provides a non-invasive diagnostic tool with virtually no harm or risk to the patient. The fact that more and more emergency medicine residents and staff physicians are being trained on the use of ultrasound makes it an even more attractive diagnostic modality.

There have been numerous publications on the use of ultrasound to help with the diagnosis of PE. However, only recently has there been a focus on a multiorgan approach by the physician at the bedside. The interpretation of data gathered by these ultrasound techniques is also simple enough that a non-radiologist or non-technician is able to make use of the information. From a thorough publication search strategy, two papers were found that examined specifically the multiorgan POCUS approach and its diagnostic power. There was also another paper that looked only at leg vein POCUS but is one of the few that actually used emergency room physicians (ERPs) as the ultrasonographers and explored the role of POCUS in determining patient risk in having a PE. Thus, it was also included in this analysis.

The three papers reviewed show that the ability for bedside POCUS to rule out PE in the absence of findings is rather poor. However, positive findings were shown to have a strong predictive value in diagnosing either PE or alternative diagnosis, if present. The two multiorgan trials agree that sensitivity is quite high for any positive findings in multiorgan POCUS (90% (82.8%–94.9%) in Nazerian et al and approaches 100% for Koenig et al). Additionally, the specificity for POCUS to predict an alternative diagnosis to explain patient symptoms was virtually 100% for both studies. The CT venography (CTV) versus emergency physician-performed ultrasound study also helped reinforce the utility of POCUS when positive findings were present. When compared with CTV, the sensitivity and specificity of an ERP conducted leg vein POCUS was 86% (42%–99%) and 100% (91%–100%), respectively.

Editor Comment

POCUS, Point-of-care ultrasound; CTV, CT venography; EPPU, Emergency physician performed ultrasound; CTPA, CT pulmonary angiography; ERP, Emergency room physician; ED, Emergency department

Clinical Bottom Line

The ability of a multiorgan POCUS approach to help risk-stratify patients with clinical signs and symptoms of PE appears very promising, but more data are needed to make a definitive statement regarding validity in clinical practice.

References

1. Nazerian P, Vanni S, Volpicelli G et al. Accuracy of Point-of-Care Multiorgan Ultrasonography for the Diagnosis of Pulmonary Embolism. Chest 2014:145:950–957.
2. Koenig S, Chandra S, Alaverdian A et al. Ultrasound Assessment of Pulmonary Embolism in Patients Receiving CT Pulmonary Angiography. Chest 2014:145:818–823.
3. Shiver SA, Lyon M, Blaivas M et al. Prospective comparison of emergency physician–performed venous ultrasound and CT venography for deep venous thrombosis. Am J Emerg Med 2010: 28:354-358.