Summary
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°C (n=40). Long-term stability samples (n=40)
were measured fresh and after storage for 19, 25 and 36 months at ≤-60°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°C was +3.8% and +2.7%,
respectively. The mean percentage change after frozen storage for 19, 25 and 36 months
at ≤-60°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 ≤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°C as well as in plasma stored for up to three years at ≤-60°C.
Keywords
D-dimer - stability - pre-analytical storage