Diagnosing deep-vein thrombosis.
Sir,

There is much interest in ward‐based screening tests that might avoid the need for imaging in patients presenting with suspected deep venous thrombosis, most of whom prove eventually not to have DVT. To be of use, such a test must have a high negative predictive value. We were interested to read of the experience in Bournemouth with computed strain‐gauge plethysmography (CSGP).1 It is now in use in 100 UK hospitals. In Bradford, we had similar results when audited formally against ultrasound, with a negative predictive value of 97%.2 However other centres have reported better and worse experiences with the same equipment, reflecting the importance of assessing the equipment in the environment in which it is to be used.

An additional screening test is only of value if the attending clinician has enough confidence in the reliability and validity of a negative result to allow discharge of the patient. Most screening investigations have a small false negative rate, and clinicians will be naturally cautious about new diagnostic tests. We therefore looked at the impact of CSGP once introduced to the medical admissions ward as a stand‐alone screening tool. The …