title: Mixing of thawed coagulation samples prior to testing: Is any technique better than another?
abstract: OBJECTIVE
  Thus study was aimed to investigate whether the mixing technique could influence the results of routine and specialized clotting tests on post-thawed specimens.
  
  
  METHODS
  The sample population consisted of 13 healthy volunteers. Venous blood was collected by evacuated system into three 3.5mL tubes containing 0.109mmol/L buffered sodium citrate. The three blood tubes of each subject were pooled immediately after collection inside a Falcon 15mL tube, then mixed by 6 gentle end-over-end inversions, and centrifuged at 1500g for 15min. Plasma-pool of each subject was then divided in 4 identical aliquots. All aliquots were thawed after 2-day freezing -70°C. Immediately afterwards, the plasma of the four paired aliquots were treated using four different techniques: (a) reference procedure, entailing 6 gentle end-over-end inversions; (b) placing the sample on a blood tube rocker (i.e., rotor mixing) for 5min to induce agitation and mixing; (c) use of a vortex mixer for 20s to induce agitation and mixing; and (d) no mixing. The significance of differences against the reference technique for mixing thawed plasma specimens (i.e., 6 gentle end-over-end inversions) were assessed with paired Student's t-test. The statistical significance was set at p<0.05.
  
  
  CONCLUSIONS
  As compared to the reference 6-time gentle inversion technique, statistically significant differences were only observed for fibrinogen, and factor VIII in plasma mixed on tube rocker. Some trends were observed in the remaining other cases, but the bias did not achieve statistical significance. We hence suggest that each laboratory should standardize the procedures for mixing of thawed plasma according to a single technique.
authors: Section of Clinical Biochemistry, University of Verona, Verona, Italy. Electronic address: dr.g.lima.oliveira@gmail.com.
authors: Gabriel
authors: G
authors: Lima-Oliveira
authors: Esoterix Inc., Englewood, CO, USA.
authors: Dorothy M
authors: DM
authors: Adcock
authors: Section of Clinical Biochemistry, University of Verona, Verona, Italy.
authors: Gian Luca
authors: GL
authors: Salvagno
authors: Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Pathology West, Westmead Hospital, Westmead, New South Wales, Australia.
authors: Emmanuel J
authors: EJ
authors: Favaloro
authors: Section of Clinical Biochemistry, University of Verona, Verona, Italy.
authors: Giuseppe
authors: G
authors: Lippi
mesh_terms: D000328:Adult; D001777:Blood Coagulation; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Blood coagulation tests; Centrifugation; Freezing; Hemostasis; Pre-analytical variability; Thawing investigative techniques