Centrally adjudicated ultrasound not always suitable for DVT screening
MedWire News: Centrally adjudicated complete compression ultrasound (CCUS) may not be suitable to screen for asymptomatic deep vein thrombosis (DVT) early after major orthopedic surgery, according to German researchers.
In 2007 Jan Beyer-Westendorf (Technical University Dresden) and colleagues published data from the VENUS (Venography vs Ultrasound) trial showing that centrally adjudicated CCUS is inferior to venography for DVT screening after major orthopedic surgery.
In the present study they aimed to determine the reasons for the inferiority of CCSU and whether thrombus characteristics such as location or size influenced their findings.
The researchers re-evaluated all false negative sonograms (n=112) from the VENUS study against the corresponding DVT-positive venograms, and compared the results with 28 pairs of concordant sonograms and venograms.
The team identified three types of diagnostic failure wherein 37.5% of discrepancies were caused by a primary documentation failure by the local sonographer, 43.7% due to failure of CCUS to show DVT, and 18.7% arising from central adjudication failure.
Among the CCUS method failures, the researchers found that approximately half were due to the small size of the thrombi (3.5-5.2 cm on average) - which prevented detection of DVT despite adequately documented CCUS.
However, proximal or distal location of DVT did not affect thrombus detection.
Given that DVT was clearly visible upon re-evaluation of the sonograms and the mean thrombi length was 9.5 cm, the researchers attributed central adjudication failure to lack of experience with central adjudicated ultrasound in asymptomatic patients.
Of note, the absolute number of pathological compression maneuvers was lower among patients in the failed adjudication group compared with the concordant group, at 3.5 versus 6.9, despite equal thrombus size in venography. It is therefore likely that "the comparatively low number of pathological compression maneuvers documented by the local sonographer contributed to the failure of central adjudication," say the researchers.
"These findings are highly important, since a number of currently ongoing clinical trials investigating new oral anticoagulants in a prophylaxis setting use centrally adjudicated venous ultrasound to detect asymptomatic or to document index events as well as recurrent VTE in VTE treatment trials," remark Beyer-Westendorf et al in the Journal of Thrombosis and Haemostasis.
They conclude: "If centrally adjudicated ultrasound is to be used in future VTE screening trials, training of local sonographers and central adjudicators needs to be intensified."
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By Laura Dean