Ultrasonography for DVT – how useful is single point augmentation?

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Aims: It is unclear whether the absence of normal augmentation of spectral Doppler flow at a single point is an accurate predictor of lower limb acute deep vein thrombosis (DVT) or whether its presence reliably excludes DVT. Our main objective was to assess the role of single point augmentation of spectral Doppler flow in the diagnosis of acute DVT. Secondary objectives included identifying the augmentation response in non-DVT diagnoses. Methods: Patients attending the ultrasound department of two hospitals during an eight-month period for investigation of suspected acute DVT were eligible. Spectral Doppler assessment of the superficial femoral vein was recorded during valsalva manoeuvre and calf compression in the asymptomatic and symptomatic legs. The Doppler waveform was characterised as 'Normal' or 'Abnormal'. Standard compression ultrasonography of the symptomatic leg was then performed with the presence of DVT or an alternative diagnosis documented. Results: 167 patients underwent ultrasound examination using the study methodology. 9 patients were subsequently excluded due to bilateral DVT or inability to tolerate calf compression. The remaining 158 patients demonstrated a mean age of 65.4 years with 28 DVTs identified (17.7% of patients). Calf compression elicited a normal response in 118/130 non DVT examinations (specificity=90.8%) and was abnormal in 18/28 DVT examinations (sensitivity=64.3%). Diminished or absent augmentation was identified in alternative diagnoses that included haematoma and Baker's cyst. Conclusions: This study demonstrates that single point augmentation of venous flow has a high specificity and negative predictive value in the assessment of suspected acute DVT. However, the sensitivity is low with 35.4% of DVTs associated with normal Doppler spectra on calf compression (the majority of these missed DVTs are isolated to the calf veins). Conversely, an abnormal augmentation response may be seen in non DVT diagnoses.