Diagnostic Test Accuracy Protocol

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Duplex ultrasound for the diagnosis of symptomatic deep vein thrombosis in the lower limb

  1. Francesca M Chappell1,
  2. Fay Crawford2,*,
  3. Alina Andras3,
  4. Steve Goodacre4,
  5. James E McCaslin3,
  6. Karen Welch5,
  7. Crispian Oates6

Editorial Group: Cochrane Vascular Group

Published Online: 20 JAN 2014

DOI: 10.1002/14651858.CD010930


How to Cite

Chappell FM, Crawford F, Andras A, Goodacre S, McCaslin JE, Welch K, Oates C. Duplex ultrasound for the diagnosis of symptomatic deep vein thrombosis in the lower limb (Protocol). Cochrane Database of Systematic Reviews 2014, Issue 1. Art. No.: CD010930. DOI: 10.1002/14651858.CD010930.

Author Information

  1. 1

    University of Edinburgh, Division of Clinical Neurosciences, Edinburgh, UK

  2. 2

    Freeman Hospital, Department of Vascular Surgery, Newcastle upon Tyne, UK

  3. 3

    Freeman Hospital, Northern Vascular Centre, Newcastle upon Tyne, UK

  4. 4

    The University of Sheffield, Medical Care Research Unit, Sheffield, UK

  5. 5

    University of Edinburgh, Public Health Sciences, Edinburgh, UK

  6. 6

    Newcastle upon Tyne Hospital Trust, Radiology, Newcastle upon Tyne, UK

*Fay Crawford, Department of Vascular Surgery, Freeman Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, High Heaton, Newcastle upon Tyne, NE7 7DN, UK. fay.crawford@nuth.nhs.uk. fay.crawford@ed.ac.uk.

Publication History

  1. Publication Status: New
  2. Published Online: 20 JAN 2014

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Table 1. QUADAS-2

Domains, signalling questions (SQ) and applicability questions (AQ)Rating criteria (information used to support risk of bias judgements)

Domain 1: Patient selection 

A. Risk of biasDescribe the methods of patient selection as given in the paper:

SQ1: Was a consecutive or random sample of patients enrolled?Yes: It is stated that the sample was consecutive or a random sample

No: It is stated that the sample was not consecutive or a random sample

Unclear: The method of sampling is ambiguous

SQ2: Did the study avoid inappropriate exclusions?Yes: The study included all symptomatic outpatients patients who had been screened with a clinical prediction rule (CPR), with or without further testing such as D-dimer, but not prior ultrasound

No: The study excluded patients who had been assessed using a CPR or who had undergone D-dimer testing or who had symptoms of DVT

Unclear: The study's exclusion criteria allow for inappropriate exclusions

SQ3: Did the study avoid inappropriate inclusions?Yes: The study included only symptomatic outpatients patients who had been screened with a clinical prediction rule (CPR), with or without further testing such as D-dimer, but not prior ultrasound

No: The study also recruited some patients with prior ultrasound (for example, in cases where previous ultrasound testing had been inconclusive), or hospital inpatients, or asymptomatic patients

Unclear: The study's inclusion criteria allow for inappropriate inclusions

AQ1: Could the selection of patients have introduced bias?Risk:

High: The patient sample is a non-random sample or a non-consecutive sample such as a convenience sample, or includes asymptomatic patients, hospital inpatients, or patients who have had a prior ultrasound

Low: The paper explicitly states that the sample was consecutive or random, that only symptomatic outpatients were recruited, and that patients were screened with a CPR with or without D-dimer, but not ultrasound

Unclear: The method of sampling is ambiguous

B. Concerns regarding applicabilityGive the paper's description of the inclusion and exclusion criteria, including setting, prior tests, symptoms here:

AQ2: Are there concerns that the included patients and setting do not match the review question?Concern:

High: The patient population and setting are different from the review question setting with regard to prior testing, previous treatments or the way in which the sample was recruited (not consecutive or a random sample). This can occur when the study uses a mixed group of patients, some of whom do not meet the review criteria. Studies that recruit patients from the inpatient setting or selected patients on the bias of atypical presentation fall into this category.

Low: The study population meets the eligibility criteria exactly as described in the Criteria for considering studies for this review section

Unclear: Not enough information is given about the study population

Domain 2: Index test 

A. Risk of biasGive the paper's description of the duplex ultrasound with or without compression and how it was conducted and interpreted, including the background of the person who carried out the test

SQ4: Were the duplex ultrasound results interpreted without knowledge of the results of the ascending venography?Yes: It is stated that the duplex ultrasound results were interpreted without knowledge of the results of the ascending venography, or the duplex ultrasound was always given and interpreted before ascending venography

No: The results of the ascending venography were known to the readers of the duplex ultrasound

Unclear: The study does not say that the duplex ultrasound was conducted blind to the results of the ascending venography or that the duplex ultrasound was always carried out prior to the ascending venography

SQ5: Did the person conducting the duplex ultrasound have expertise comparable to a radiologist?Yes: The person conducting the duplex ultrasound was a radiologist or had extensive experience and training (e.g. ultrasonographer, vascular scientist)

No: The person conducting the duplex ultrasound was not a radiologist and did not have sufficient experience and training

Unclear: The expertise and background of the duplex ultrasound readers is not clear

AQ3: Are there concerns that the duplex ultrasound in its conduct or its interpretation have introduced bias?Concern:

High: The duplex ultrasound was not read blind to the results of the ascending venography by a person with expertise comparable to a radiologist

Low: The duplex ultrasound was read blind to the results of the ascending venography by a person with expertise comparable to a radiologist

Unclear: The study does not give sufficient information to conclude that the duplex ultrasound was read blind to the ascending venography or by a person with expertise comparable to a radiologist

B. Concerns regarding applicability

AQ4: Is there concern that the duplex ultrasound in its conduct, or interpretation differ from the review question?Concern:

High: The duplex ultrasound was not read blind to the results of the ascending venography by a person with expertise comparable to a radiologist

Low: The duplex ultrasound was read blind to the results of the ascending venography by a person with expertise comparable to a radiologist

Unclear: The study does not give sufficient information to conclude that the duplex ultrasound was read blind to the ascending venography or by a person with expertise comparable to a radiologist

Domain 3: Reference standard 

A. Risk of biasGive the paper's description of the reference standard including how it was conducted and interpreted and the background of the reader

SQ5. Is the reference standard likely to classify correctly the target condition?Yes: The study reports that either ascending venography, CT venography, or MR venography was performed for all participants

No: Not all patients received ascending venography, CT venography, or MR venography. For example, a definite diagnosis may have been decided by a repeated ultrasound scan

Unclear; It is unclear whether all patients underwent either ascending venography, CT venography, or MR venography

SQ6: Were the reference standard test results interpreted without knowledge of the duplex ultrasound results?Yes: The person classifying the reference standard results was unaware of the duplex ultrasound results

No: The person classifying the reference standard results was aware of the duplex ultrasound results

Unclear: Details about the person classifying the reference standard results are not reported

SQ7: Did the person conducting the reference standard have expertise comparable to a radiologist?Yes: The person conducting the reference standard was a radiologist, sonographer or vascular scientist with extensive experience in performing duplex ultrasound scans

No: The person conducting the reference standard was not a radiologist, sonographer or vascular scientist and did not have expertise in performing duplex ultrasound

Unclear: The expertise and background of the reference standard readers is not clear

AQ5: Could the reference standard, its conduct, or its interpretation have introduced bias?Risk:

High: The reference standard was not carried out to the required standard by a person with expertise, or it was carried out with knowledge of the duplex ultrasound results and/or the period for clinical follow-up is longer than 3 months

Low: The reference standard was carried out by a radiologist or a person with sufficient expertise without knowledge of the duplex ultrasound results

Unclear: Whether the reference standard was read blind to the results of the duplex ultrasound, or the expertise of the reader is unknown

B. Concerns regarding applicability

AQ6: Are there concerns that the target condition does not match the question (as defined by the review question)?Concern:

Yes: The way the reference standard was conducted meant that a patient with DVT could have been missed, or a patient with no DVT could have been diagnosed with DVT

No: The reference standard was conducted appropriately by the appropriate person

Unclear: The conduct of the reference standard is not clear enough to conclude whether DVT was accurately diagnosed

Domain 4: Flow and timing  

A. Risk of biasDescribe the reasons why any patients recruited into the study did not contribute to the 2x2 table (i.e. patients who did not undergo the reference standard and/or duplex ultrasound) referring to the flow diagram:

SQ8: Was there an appropriate interval between the index test and the reference standard?Yes: The time interval between ultrasound and reference standard was less than 7 days

No: The time interval between ultrasound and reference standard was more than 7 days

Unclear: The time interval between ultrasound and reference standard was not reported, or reported ambiguously (for example, only the mean or median time is reported, without an indication of the maximum time between tests)

SQ9. Did all patients receive the reference standard?Yes: All patients received the reference standard regardless of the results of prior tests

No: Patients were referred for the reference standard according to their ultrasound results

Unclear: It is not clear whether all patients received the reference standard

SQ10: Did all the patients receive the same reference standard?Yes: All patients underwent either ascending venography, or all underwent CT venography, or all underwent MR venography

No: The study includes patients who did not undergo ascending venography, or CT venography, or MR venography, and may have had a repeat ultrasound or follow-up instead

Unclear: The study may have included patients who had a repeat ultrasound or follow-up instead

SQ11: Were all patients included in the final analysis?Yes: All patients enrolled contributed to the 2x2 table

No: There are some patients enrolled who did not contribute to the 2x2 table

Unclear: It is not clear whether there were patients recruited, but not included in the study report or 2x2 table

SQ12: Did the patients receive anticoagulant therapy between the index test and reference standard?Yes: Some patients started anti-coagulant therapy between the ultrasound and the reference standard

No: Patients did not start anticoagulant therapy until after both ultrasound and the reference standard tests had been completed

Unclear: It is not reported when patients started any anticoagulant therapy

AQ7: Could the patient flow have introduced bias?Risk:

Low: All patients recruited underwent both ultrasound and the reference standard in a timely manner and did not start anticoagulant therapy until after both tests had been completed

High: Not all patients recruited received both tests, or the time between tests allowed for disease progression to occur, or patients started anticoagulant therapy between tests

Unclear: The time interval between tests is not clear, the treatment status of the patients is not clear, or whether all patients received both tests is not clear