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

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 (R) 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 (R) 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 (R) D-dimer as part of the routine DVT investigation. Using the same samples, D-dimer estimation was also performed on the STalia (R) D-Di for comparison. Across a wide range of data (Vidas 83-5656) and (STalia (R) < 200-> 4000), there was good agreement between the two methods. Using cutoff's of 500 mu g/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 (R) and another 6% (6/100) were positive on the STalia (R) 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 (R) 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.