Chapter 14 - routine and point-of-care testing in hematology

manual cell counts definition

often done on fluids that aren’t blood b/c consistency, uses hemocytometer

aspects of hemocytometer

two raised surfaces, 3mm x 3mm (9 mm² total), 9 squares divided into 16 smaller squares each, center square has 25 smaller squares

what cells to count in manual cell count

top-left rule, count cells that touch top and left edges, not the bottom and right, count all the ones not touching edges too; count should match within 10% on each side of chamber

sources of error in manual cell count

improperly cleaned hemocytometer, diluting fluid contaminated, over filled or under filled chamber, not allowing cells to settle for 10 minutes, NRBS not lysed by diluting fluid; check accuracy by WBC estimate on peripheral smear

microhematocrit

done by analyzer, hematocrit is volume of packed RBC that occupy given volume of whole blood, reported in %, fill tube-seal with clay-centrifuge-compare to chart

what does microhematocrit tube look like

from bottom to top clay-RBC-buffy coat (WBC and plt)-plasma; read by top of plasma and roll until RBC hits line

rule of three

hct = hgb x 3

reticulocyte counts

included in total RBC count, note how many are reticulocytes, mix blood w/ new methylene blue and incubate 3-10 min, if a patient has low hematocrit use a correction factor

erythrocyte sedimentation rate (ESR)

allow RBC to settle 1 hour, measure distance they have fallen, used to screen for inflammatory diseases; old method was Westergren, now ves-matic or iSed (only 20 seconds)