The platelet count from the automated cell counter is 80 ´ 109/L. Platelet satellites around neutrophils are observed on the blood film estimate. A sodium citrate tube is drawn, and the count reads 300 ´ 109/L from the cell counter

What platelet count ´ 109/L should be reported?

a. 80
b. 300
c. 330
d. The estimated count from the blood film

ANS: C
The platelet count from the automated cell counter cannot be accepted because it is falsely low because of the platelet satellites seen on the blood film. This is an occasional problem in some patients when their blood is drawn in ethylenediaminetetraacetic acid (EDTA). Drawing the blood into sodium citrate eliminates the satellites. However, this tube results in a dilution of the blood (nine parts blood plus one part anticoagulant = 9:10 dilution of blood). The platelet count from the instrument must therefore be multiplied by 1.1 (= 10/9) to obtain the valid platelet count. Therefore the platelet count = (300) ´ (1.1) = 330 (´ 109/L).