Vigorous Mixing May Effect Blood Results

The effect of tube mixing techniques on the quality of diagnostic blood specimens collected in vacuum tube systems by venipuncture has been evaluated.

The accurate mixing of blood in tubes with anticoagulant- or clot activator additives is essential for their effectiveness and may influence the reliability of test results and thereby affect the diagnostic outcome, the follow-up, and the therapeutic management of patients.

Clinical biochemists at the University of Verona (Italy) collected blood from 100 volunteers for routine coagulation, immunochemistry, and hematological testing from April 1, 2012, to May 1, 2012. The blood was put into six vacuum tubes: two 3.6 mL vacuum tubes containing 0.4 mL of buffered sodium citrate; two 3.5 mL vacuum tubes with clot activator and gel separator; and two 3.0 mL vacuum tubes containing dipotassium ethylenediaminetetraacetic acid (K2EDTA). All vacuum tubes, each of one additive type were processed through two different procedures.

The standard procedure was blood specimens in K2EDTA- or sodium citrate-vacuum tubes were gently inverted five times whereas the specimens in tubes with clot activator and gel separator were gently inverted ten times. The second procedure consisted of all the blood specimens were shaken up vigorously during three to five seconds independently of the additive type inside the tubes.

Routine hematology, clinical chemistry, and immunochemistry and coagulation tests were performed. The results of the investigation for all the parameters showed that no significant differences were detected between the standard procedures versus the vigorous mix. Only a visual alteration with the presence of foam on the top was shown by all the tubes mixed vigorously before centrifugation. The serum tubes from vigorous mixing procedure shows a “blood ring” on the tube top after stopper removal.

The vacuum tubes used were manufactured by Terumo Europe (Heverlee, Belgium). The authors concluded that primary blood tubes vigorous mixing does not promote laboratory variability and suggest that similar evaluation should be done using other brands of vacuum tubes by each laboratory manager. The study was published in the February 2013 issue of the journal Clinical Biochemistry.

Related Links:
University of Verona
Terumo Europe