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.

Evaluation of Plasma d-Dimer Plus Fibrinogen in Predicting Acute CVST

“…The reason for this discrepancy remains unclear and may be attributed in part because of different mechanisms of origination and progression seen when peripheral DVTs are compared with that of thrombi found in CVST. Additional factors such as differences in age and systemic disease conditions in the patients can also explain the aforementioned discrepancy, among other unexplained factors (35,36). Though d-dimer elevation is associated with most thrombotic vascular diseases, it should be noted that it stands to be a highly sensitive yet very non-specific thrombus localization test (36).…”

The Role of D-dimer Testing in Patients with Suspected Venous Thromboembolism

“…The calibration curve usually covers a wide range of concentrations, but the upper reference range of normal values and the detection limit for VTE exclusion often lies in the lower part of the calibration curve, where the signal is weaker. 15,16…”

Response to the Comments on ‘Point of Care D-Dimer Testing in the Emergency Department–A Bioequivalence Study’ and Erratum to the Results

“…A study on bioequivalence between the two assays was not enough to make an informed decision to replace one test with the other, a conclusion also supported by Sukhu et al [8] in their study.…”

“…As pointed out by Sukhu et al [8], discordant values are increasingly obtained near the cut-off levels leading to mismatched results between the two assays, therefore, a larger study would be required before implementing a new methodology in a clinical setting. A study on bioequivalence between the two assays was not enough to make an informed decision to replace one test with the other, a conclusion also supported by Sukhu et al [8] in their study.…”