Comparison of an immuno-turbidometric method (STalia D-DI) with an established enzyme linked fluorescent assay (VIDAS) D-dimer for the exclusion of venous thromboembolism

Abstract

The use of d-dimer tests for the exclusion of venous thromboembolism is an important advance in clinical practice and also has economic benefits. The Stalia D-Di (Diagnostica Stago, Asnieres, France) is a semi automated system for the quantification of d-dimer using an immuno-turbidometric method incorporating a suspension of latex microparticles coated with two different monoclonal antibodies specifically targeted against human d-dimer fragments. Results are available rapidly in <10 min compared with 35 min for the established VIDAS D-dimer automated enzyme-linked immunosorbent assay (ELISA, BioMerieux, Basingstoke, UK). During November and December 2005, 100 consecutive patients attending the outpatient deep venous thrombosis (DVT) clinic were tested using the VIDAS D-dimer as part of the routine DVT investigation. Using the same samples, D-dimer estimation was also performed on the STalia D-Di for comparison. Across a wide range of data (Vidas 83-5656) and (STali <200->4000), there was good agreement between the two methods. Using cutoff's of 500 microg/l fibrinogen equivalent units (Keeling et al., 1999), 42% (42/100) patients were negative (<500) and 46% (46/100) were positive (>500) on both systems. Six per cent (6/100) were positive on the Vidas but negative on the STalia and another 6% (6/100) were positive on the STalia but negative on the Vidas. In conclusion, 88% (88/100) of patients showed agreement and in the other 12% (12/100), one had a DVT as identified by Compression ultrasonography (CUS). In this study, there were seven patients with a DVT as identified by CUS and they all scored as 'likely' on a pretest clinical probability score and so negative D-dimer would not be used clinically to rule out the disease. The Vidas is a well established instrument for D-dimer measurement in outpatient DVT clinics, and in this small study the STalia compares very well and therefore would fit into an outpatient setting for D-dimer measurement. But ideally a larger study would be required before implementing new methodology in a clinical setting.