Age-adjusted D-dimer cut-off leads to more efficient diagnosis of venous thromboembolism in the emergency department: a comparison of four assays.

Essentials Age-adjusted D-dimer cut-offs decrease the false positives in the elderly. Four D-dimer assays were compared in venous thromboembolism outpatients in an emergency ward. Age-adjusted cut-off resulted in improved specificity with maintained sensitivity for all assays. There was a substantial decrease in false positive results, especially in the older population. SUMMARY: Background The study compares different D-dimer assays and age-adjusted cut-offs in outpatients with suspected venous thromboembolism (VTE). The plasma concentration of this sensitive biomarker is increased by activated coagulation, but also by several conditions that are linked to an increased risk of VTE. One such condition is old age, which poses a common clinical problem where many prefer not to analyze D-dimer in elderly patients. Age-adjusted cut-offs have been validated for both deep venous thrombosis (DVT) and pulmonary embolism, aiming to increase specificity without notably decreasing sensitivity. Objectives We evaluated four common D-dimer assays in parallel, with and without applying age-adjusted cut offs for VTE. Patients/methods The prospective single-center study was conducted in 940 outpatients attending the emergency department with clinically suspected pulmonary embolism or DVT. Four automated D-dimer assays were compared (Siemens INNOVANCE® , Roche Tina-quant, Medirox MRX and STA® -Liatest® D-Di PLUS). Results All assays performed with areas under the ROC curve (AUC) > 0.9 and maintained their sensitivities after implementation of age-adjusted cut-offs. Specificities increased by 6-7% and number needed to test decreased by < 0.3. The rate of false positive results decreased by 6% overall and by 10-20% for patients ≥ 70. Conclusions Age-adjusted cut-offs resulted in maintained high sensitivity and a modest improvement in specificity and number needed to test for all evaluated D-dimer assays. There was a significant reduction in false positive results, which reflects avoidable unnecessary imaging without any compromise of clinical safety. This suggests a potential to benefit the management of VTE in elderly patients, both clinically and economically.

Evaluation of small-volume tubes for venous and capillary PT (INR) samples.

INTRODUCTION: Frequent PT (INR) testing may represent a problem for patients on warfarin treatment, and capillary or small-volume tubes may be more appropriate for such patients. A demand for small-volume tubes also comes from pediatric wards. Yet, while various small-volume tubes are available, they have not been properly evaluated. METHODS: Three small-volume tubes were tested (MiniCollect 3.8% citrate, MiniCollect 3.2% citrate and Microvette EDTA) and compared with a standard 4.5-mL 3.2% citrated tube. Samples were taken by venipuncture from the back of the hand and by capillary sampling from the tip of the finger. The measures were compared with those after standard venipuncture of the arm fold. A total of 180 samples, using different combinations of tubes and sampling sites, were collected from 30 volunteers. RESULTS: There were no differences in the results obtained using citrate tubes for venous samples in comparison with those obtained by standard sampling, while the results when using EDTA tubes were not comparable to those obtained by standard sampling (P < 0.001), expressing systematically lower values (by about 10%). The results observed after capillary sampling were significantly different to those obtained after standard sampling. CONCLUSIONS: The MiniCollect 3.2% tube may be used for PT (INR) venipuncture samples when withdrawal of a small amount of blood is preferable, while EDTA tubes should not be used for PT (INR) testing.