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Three Part Question

In [patients with suspected DVT based on clinical signs/symptoms] does [Emergency Physician performed ultrasound] have [similar accuracy to department of radiology ultrasound in identifying proximal lower limb DVT]

Clinical Scenario

A 43 year old female presents to the ED with symptoms and signs suggestive of DVT. According to local protocol she requires a Doppler ultrasound study to diagnose or exclude a DVT. Unfortunately there is no scan available from radiology for 2 days. One of the new ED registrars is trained in ultrasound to level 2, including peripheral vascular studies. You wonder if there is evidence that the scan performed by the EM trainee will be equivalent to that performed in the radiology department, thus avoiding delay in diagnosis and possible unnecessary treatment.

Search Strategy

Ovid MEDLINE 1948-November 2011
Deep vein thrombosis.mp or DVT.mp or exp Venous Thrombosis/) and (ultrasound.mp or ultrasonography.mp or exp Ultrasonography, Doppler/ or exp Ultrasonography, Doppler, Pulsed/ or exp Ultrasonography/ or exp Ultrasonography, Doppler, Duplex/ or exp Ultrasonography, Doppler, Color/) and (emergency physician.mp. or emergency department.mp or Accident & Emergency.mp. or exp Emergency Service, Hospital/ or exp Emergency Medical Services/ or exp Emergency Medicine/ or exp Emergencies/ or exp Physicians/ exp Medical Staff, Hospital/ or exp Triage/)

Search Outcome

125 papers identified of which 11 were relevant. 4 were excluded as they either included venography as the department of radiology investigation or included patients with suspected PE.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Farahmand 2011 Iran	74 adult patients presenting with painful/swollen lower limbs	Observational prospective	Accuracy of ED 2 point CUS vs. Radiology dept duplex (proximal leg)	Sensitivity 100% Specificity 100% PPV 100% NPV 100%	Small sample size Convenience sample No clear exclusion criteria.
Crisp J 2010 USA	199 patients with suspected lower extremity DVT.	Observational prospective	2 point CUS in ED compared to Radiology dept duplex performed within 3 hours of the ED scan.	Sensitivity 100% Specificity 99%	Convenience sample Operator bias due to wide range in number of scans per operator (1-29)
Kline JA 2008 USA	183 adult patients with one or more defined clinical signs of DVT.	Observational prospective	Accuracy of 3 point CUS in ED vs Radiology dept whole leg scan. Patients followed up for 30 days for DVT/PE.	Sensitivity 70% Specificity 89% Higher diagnostic accuracy in patients who were high risk and in scans performed by EPs who enrolled >3 patients.	Lower prevalence of DVT than other studies. Operator bias - scanner knew risk classification. 29 patients lost to follow up. Convenience sample. Whole leg duplex dept of radiology scan vs 3 point proximal ED scan with optional use of colour flow No calculation of sensitivity of ED scan for proximal clots only.
Theodoro D 2004 USA	156 patients with suspected DVT.	Observational prospective	Time to disposition as primary outcome. Accuracy as secondary outcome. 5 pre-trained EP’s using 2 point CUS. Time recorded from triage to results of scan.	ED time to disposition 95 mins vs 220 mins for radiology scan. Agreement in 154/156 scans. 2 false positives.	Variable prior experience of scanners. Unclear value of ED US when there is 24 hour radiology cover. Unclear patient pathways/time to transfer to radiology department.
Frazee B et al. 2001 USA	84 adult patients with provisional diagnosis of DVT.	Observational prospective	ED performed 2 point CUS vs vascular lab duplex scan. Positive, negative or indeterminate scan result.	Sensitivity 88.9% Specificity 75.9% NPV 95.7% PPV 53.3%	Convenience sample No formal inclusion/exclusion criteria. Large number indeterminate scans with operator learning curve. Small sample size.
Blaivas M et al 1999 USA	112 patients who met high risk criteria for DVT.	Observational prospective	Evaluated accuracy and speed of ED 2 point CUS compared to duplex by Radiology dept.	Sensitivity – 74% Specificity – 93% PPV – 50% NPV – 97% Average scan time 3.28 mins (1.02 to 18.20)	Median examination time did not account for set up time nor was compared to time for scan in radiology dept. Convenience sample Proximal leg only scan in ED vs whole leg in radiology dept – 2 calf thrombi without proximal clot found (no calculation of sensitivity of ED scan in identifying clots that require treatment)
Jolly B 1997 USA	23 patients with suspected DVT presenting out of hours.	Observational retrospective	To assess feasibility of 2 ED doctors trained in hospital radiology dept performing Doppler US. ED scans compared with dept of radiology scans.	Sensitivity 100% Specificity 75% PPV 78% NPV 100%	Small sample size. 8/23 lost to follow up – either critically unwell/improved/DNA. Some assessment for distal DVT in both ED and dept of radiology but not uniform Variable use of colour flow in ED and not specified if 2 or 3 point CUS. Radiology dept not blinded to ED scan results.

Comment(s)

Duplex ultrasound has now replaced venography as the most widely used diagnostic test for DVT. This study involves examining the venous system for compressibility, colour flow and waveform to determine the presence of clot. It may be performed at the femoral vein just below the inguinal ligament and popliteal veins in the popliteal fossa (2 point CUS), these plus mid shaft femoral vein (3 point CUS), step wise from femoral vein just below the inguinal ligament to (popliteal) trifurcation or most comprehensively as the latter but then including Duplex scans to the deep venous system of the lower leg. This latter comprehensive study may take 20-30 minutes to complete, as opposed to less than 5 minutes for the shorter protocols. In the studies described above most commonly Emergency physicians performed limited scans while vascular labs and radiology departments perform limited or comprehensive scans, as dictated by local protocol. Most medical practitioners would treat proximal DVTs but not those isolated to the lower limb. In the studies cited above some have compared focused ED scans to more comprehensive whole leg scans performed in radiology or vascular labs. These studies will identify more DVTs but not necessarily ones where there is widespread agreement on anticoagulation. The studies may not report the number of extra scans identified by the comprehensive scan that required treatment. Emergency physicians can accurately diagnose proximal DVT with good sensitivity and specificity in comparison to radiology department imaging. We used radiology department ultrasound for comparison, as this is the standard used in current practice to determine treatment. Some studies suggest a reduced time to disposition with scans performed by the Emergency physicians. All the papers examined were observational studies using convenience sampling methods thus increasing the likelihood of bias especially in patient selection. The amount of training required and any clinical advantages of emergency department scanning have yet to be clearly defined.

Clinical Bottom Line

From the evidence available it appears that Emergency physicians can be trained to perform focused Duplex ultrasound to identify lower limb DVT with similar accuracy to radiology departments / vascular labs. Further research into the amount and type of training required to reach an acceptable level of accuracy is required.

Level of Evidence

Level 2 - Studies considered were neither 1 or 3.

References

1. Farahmand S, et al The accuracy of limited B-mode compression technique in diagnosing deep venous thrombosis in lower extremities. Am J Em Med Jul;29(6):687-90.
2. Crisp J et al Compression Ultrasonography of the Lower Extremity With Portable Vascular Ultrasonography Can Accurately Detect Deep Venous Thrombosis in the Emergency Department Ann Emerg Med. Dec 2010;56(6):601-10.
3. Kline JA et al Emergency clinician-performed compression ultrasonography for deep venous thrombosis of the lower extremity. Ann Emerg Med. 2008 Oct;52(4):437-45
4. Theodoro D et al Real-time B-mode ultrasound in the ED saves time in the diagnosis of deep vein thrombosis (DVT). May 2004;2 Am J Emerg Med. May 2004;22(3):197-200.
5. Frazee BW et al Negative emergency department compression ultrasound reliably excludes proximal deep vein thrombosis. Acad Emerg Med. 1998;5:406-7.
6. Blaivas M et al Lower-extremity Doppler for deep venous thrombosis--can emergency physicians be accurate and fast?. Acad Emerg Med. Feb 2000;7(2):120-6.
7. Jolly B et al Color Doppler ultrasonography by emergency physicians for the diagnosis of acute deep venous thrombosis. Acad Emerg Med. 1997 Feb;4(2):129-32.