Test 3: Manual Platelet Counts and Estimates

Question 1

how do you estimate the platelet count?

Answer 1

-take the average number of platelets counted per 100X field (having counted three more fields)
-multiply the average value times 20,000

Question 2

Normally, there should be between _____ and _____ platelets per field or ______________/mm^3

Answer 2

7-23 or 150,000 to 450,000/mm^3

Question 3

what platelets should be reported?

Answer 3

platelets approaching the size of erythrocytes or larger or abnormal (macrothrombocytes) should be noted if they appear frequently (one or more in every other field)

Question 4

when doing a manual platelet count, ____________ blood is added to the Thrombo-TIC Unopette, which contains 1% ammonium oxalate. The composition is such that it lyses the red cells but preserves platelets and leukocytes. The solution will be clear red and counting can proceed. A hemacytometer and microscope are used to count platelets.

Answer 4

whole

Question 5

equipment for manual Platelet Count?

Answer 5

-Hemacytometer
-22 mm^2 cover slip
-Thromno-TIC reservoir
-Thrombo-TIC capillary tube
-Petri dish with moistened gauze

Question 6

Because platelets are difficult to view, what should be done to optimize viewing?

Answer 6

low-intensity light along with constant fine focus adjustments.

Question 7

The calculation for hemacytometer regardless of the type of cells (WBC, RBC, platelets)

Answer 7

Total # of cells counted x dilution factor /
(# of large squares counted) x 0.1 mm (depth) = cells counted

Question 8

Why should plastic or siliconized glass syringes be used instead of glass?

Answer 8

platelets become activated by contact with glass and will aggregate causing a false reduction.

Question 9

Why should a new specimen be collected when clumps are seen?

Answer 9

tissue trauma during blood collection reduces the accuracy of the count.

Question 10

how are platelet counts checked?

Answer 10

an estimate with a peripheral blood smear