[Effect of sample volumes and utilized anticoagulants on the measurement of complete blood counts including 3-part differentials using capillary blood].

We collected the different volumes of venous blood(60 microL, 125 microL, 250 microL and 500 microL) into micro sample cups from respective volunteer to compare complete blood count (CBC) among 4 sample volumes, and found that 60 microL of sample volume seemed enough for CBC measurement using Microsemi LC-667 CRP (Horiba Co.). Subsequently, we measured CBC using 60 microL of peripheral blood after combining one of the 3 capillary tubes (heparin coated, EDTA coated and plain) with either EDTA coated or plain micro sample cups to examine the effect of anticoagulants contained into these commercially available maneuvers for capillary blood sampling. When we used the plain micro sample cup, platelet aggregation and false increase of white blood cell(WBC) count were observed irrespective to the combination of capillary tubes. We also tried whether commercially recommended volume (250 microL) of sample could be obtained by either fingertip or earlobe puncture from volunteers, and found that 7 of 16 fingertip and only 1 earlobe punctures could achieve sufficient volume. Whereas, at least 60 microL of sample were available more than 80% of volunteers by both methods, and CBC data obtained from these lesser samples obtained by fingertip puncture showed no statistically significant differences when compared with those of conventional venous samples (2 mL). From these findings, we concluded that at least 60 microL of capillary blood obtained from fingertip then collected into EDTA coated micro sample cup was enough to measure CBC using Microsemi LC-667 CRP.