Incomplete filling of spray-dried K₂EDTA evacuated blood tubes: impact on measuring routine hematological parameters...

Because there is little published evidence on the effects of incomplete filling of K₂EDTA evacuated blood tubes on routine hematological testing, this original study aimed to provide updated information on this preanalytical aspect.

The study population consisted of 17 ostensibly healthy volunteers. Blood was drawn by venipuncture with a 10 mL syringe and dispensed in varying amounts (0.2, 0.5, 1.0, 2.0, and 3.0 mL) into 3.0 mL blood tubes containing spray-dried 5.4 mg K₂EDTA. All tubes were gently mixed and used to perform routine hematology tests on the Sysmex XN-10. Clinically significant variations were defined when the limits of desirable specifications of bias derived from biologic variation were exceeded.

The desirable bias was exceeded in 33 % filled tubes (1.0 mL) for hematocrit and MCV (increased values) and for MCHC (decreased values), while it was exceeded in 17 % filled tubes (0.5 mL) for hemoglobin, hematocrit and MCV (increased values), and for MCHC (decreased values). Finally, the variation of values was higher than the desirable bias for RBC, hemoglobin, hematocrit and MCV (increase), and for MCHC and MPV (decrease) in 7 % filled tubes (0.2 mL). No clinically significant variations were observed in tubes filled up to 67 % of their nominal volume (i.e., 2.0 mL).

Consideration should be given to reject spray-dried K₂EDTA blood tubes that contain a blood volume <67 % of the nominal fill volume, as biased laboratory data in these samples may interfere with clinical decision making and care management.