Long- and short-term in vitro D-dimer stability measured with INNOVANCE D-Dimer.

In vitro D-dimer stability in plasma is widely assumed, but has not yet been documented by systematic studies using samples covering a wide range of D-dimer. We investigated the short- and long-term stability of D-dimer in clinical citrated plasma samples with normal and pathological levels. The short-term stability was analysed by measuring D-dimer fresh, after storage of plasma for 4 hours at room temperature (RT) and after an additional 24 h storage at +2 to +8 degrees C (n=40). Long-term stability samples (n=40) were measured fresh and after storage for 19, 25 and 36 months at < or =-60 degrees C. The effect of repeated freezing was analysed by measuring samples (n=50) fresh and after four consecutive freeze-thaw cycles. D-dimer was measured on the BCS System using the INNOVANCE D-Dimer assay (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany). D-dimer values at baseline ranged from 0.23-22.2 mg/l FEU. The mean percentage change after storage for 4 hours at RT and additional 24 hours at +2 to +8 degrees C was +3.8% and +2.7%, respectively. The mean percentage change after frozen storage for 19, 25 and 36 months at < or =-60 degrees C was -11.7%, -4.8% and -9.3%, respectively. The small decrease of D-dimer values after frozen storage was not time-dependent. Repeated freezing did not significantly alter D-dimer values (mean change < or =5%). The data demonstrate stability of D-dimer in plasma prior to freezing for up to 4 hours at RT and for up to 24 hours at +2 to +8 degrees C as well as in plasma stored for up to three years at < or =-60 degrees C.