| Sumario: | Objectives: The present study aimed to examine whether the D-dimer stability time can be extended from 4 hours to 6 or 8 hours at room temperature to account for late arrival samples and add-on test requests received after 4 hours. Methods: Three citrate blood tubes were collected from 25 patients. For each patient, a baseline tube was centrifuged and tested for D-dimer upon arrival (within 4 hours). This baseline tube was then repeatedly tested at 6 hours and 8 hours post-sample collection. The other two tubes were stored horizontally at room temperature until 6 hours and 8 hours post-sample collection, at which they were centrifuged and tested, respectively. All tests were analysed with the INNOVANCE D-Dimer assay. Results: The D-dimer levels at baseline ranged from less than 190 μg/L FEU to 10512 μg/L FEU. The mean percentage changes at 6 hours and 8 hours were all below the clinically acceptable cut-off of 10% compared with the baseline. Specifically, for centrifuged samples, a decrease of 2.39% and 2.23% were found after 6 and 8 hours, respectively. For uncentrifuged samples, a decrease of 2.83% and 1.93% were observed at 6 and 8 hours, respectively. Results from each tested condition all met the allowed limit of performance in EFLM (European Federation of Clinical Chemistry and Laboratory Medicine). Further analysis using Passing-Bablock regression showed excellent agreement between D-dimer levels at baseline and D-dimer levels after 6-and 8-hours storage. Conclusion: Our study demonstrated that the stability of D-dimer at room temperature can be reliably extended to 8 hours for both centrifuged and uncentrifuged whole blood samples.
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