Tests could avoid unnecessary DVT investigations in elderly, frail
MedWire News: Two age-adapted D-dimer tests can be safely used to exclude deep-vein thrombosis (DVT) in elderly patients in primary care, suggests research published in the BMJ.
The tests rule out DVT in many more patients - who can then avoid going into hospital for unnecessary additional testing - compared with the standard D-dimer test, without increasing the chance of a case being missed.
Researchers from the University of Utrecht in the Netherlands and led by Henrike Schouten evaluated use of two D-dimer tests previously developed in secondary care, one based on an age-dependent cut off for over-50s and one based on a fixed cut off for patients aged over 60, using data for 1374 primary care patients (mean age 59.3 years) with suspected DVT.
Among 647 (47%) patients who had a low clinical probability of DVT according to the Wells score, the age-dependent cut off value for D-dimer concentration (age in years multiplied by 10 µg/L for patients aged over 50 years) excluded DVT in 309 (47.8%) patients, an additional 37 (5.7%) patients compared with the conventional 500 µg/L cut off.
This was at the cost of one single extra case missed, as the number of false negatives went up from two to three, or by 0.2%.
Meanwhile, the fixed cut off value of 750 µg/L in participants aged 60 years and older excluded DVT in 307 (47.4%) patients - an additional 35 patients - without missing any extra cases.
The increase in diagnostic efficiency increased with age, the authors say. The proportion of patients aged 70-80 years in whom DVT could be excluded increased from 30.6% using the conventional test to 45.0% with the age-dependent test and 45.9% using the cut off of 750 µg/L. In patients over 80 years old, the corresponding proportions were 21.0%, 35.5% and 33.9%, respectively.
"These findings are important, since further diagnostic testing can thus be avoided in these often frail elderly patients," write Schouten and colleagues.
"Before implementing these strategies in daily practice, a formal, prospective impact study would need to assess the potential benefits of using an age-adapted, D-dimer cut off value in daily patient care," they conclude.
By Caroline Price