Page 709 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

CHAPTER 32 ■ Laboratory Manual: Manual Procedures in Hematology 693

COAGULATION PROCEDURES (continued)

2. Conventional microscope or phase-contrast hemocytom- Calculations

eter an coverslip. T is type o hemocytometer has a at T e number o platelets per microliter is:

bottom rather than the concave type use or counting

other cellular elements. otal ilution volume

3. Petri ish with a piece o moistene f lter paper inserte average

in the bottom. no.o
µ

4. Phase contrast microscope an lens paper. Platelets/ L= platelets × ccorrelation × correlation
5. Microscope sli es an Wright-Giemsa stain. T is is an in 5squares actor actor

optional but recommen e quality control proce ure.

T e ilution an volume correction actors are erive in
Quality Control the same manner as or the erythrocyte count.

Quantitative results shoul be checke against a well-ma e, Example: I the average total o the platelets counte in f ve

staine peripheral smear. squares is 20, the platelet count per microliter is:

×

×
µ

,
Procedure 20 200 50 = 200 000/Lor
1. T oroughly mix the bloo sample an f ll the hemo- 200 10 /L (SI units )
9
×
cytometer accor ing to the manu acturer’s irections.
Note: to loa or charge the counting chamber, the f rst Reporting Results
ew rops o the ilution are le in the bore o the pipette Te re erence value is 150,000 to 400,000/µL or 150 to

shoul f rst be expelle . Fill one si e o the counting 400 × 10 /L (SI units).
9
chamber with the platelet ilution, being care ul not to Sources of Error

let any o the solution run over the e ges into the sur-
roun ing grooves. Repeat this proce ure, using the sec- A variety o technical errors can pro uce incorrect results.

on T rombo- IC ilution vial, an f ll the opposite si e T ese inclu e the age o the specimen, clumping o platelets,
o the counting chamber. ebris in the iluting ui , platelet a herence to glass, an

2. Place the hemocytometer into a Petri ish with moistene incorrectly iluting the specimen.
f lter paper on the bottom an allow to stan or 15 to 30 An even istribution o platelets through the counting

minutes. Patient i entif cation shoul be inclu e on the area is critical. Clumping o the platelets results rom ina -
Petri ish. T e platelets will settle in the counting cham- equate mixing or poor technique. I clumps are seen, the

ber an loss o moisture will be prevente by covering the sample must be re ilute an recounte .
hemocytometer. In cases o thrombocytopenia, the ilution may have to be

3. Care ully wipe o any moisture that may have accumu- increase . T e new ilution actor must be inclu e in the cal-
late on the bottom o the hemocytometer be ore plac- culation ormula. In cases o thrombocytosis, ewer squares

ing it on the microscope stage. Using the 10× objective can be counte . In either thrombocytopenia or thrombocy-
(low power), ocus the microscope on the large mi le tosis, re er to the manu acturer’s package insert or a itional

square o the counter chamber. T e backgroun shoul instructions on changing an calculating platelet counts.
appear ark, whereas the platelets, leukocytes, ine Clinical Applications

ebris, an markings o the hemocytometer appear T e enumeration o platelets has now become a routine com-
illuminate . ponent o the automate complete bloo cell count (CBC).

4. Switch to the 43 to 44× objective (high power) an re o- In cases o severe thrombocytopenia or whenever cellular
cus, i necessary, with only the f ne a justment. Re uce the abnormalities may be spuriously a ecting the automate

amount o light reaching the microscope stage. count, a manual count shoul be per orme .
5. T e platelets shoul appear roun or oval in shape an Selected Quantitative Disorders of Platelets

give a aintly purple-orchi appearance. Any extraneous
ebris will appear to be re ractile when the epth o ocus

is altere using the f ne a justment. Increased Platelets Decreased Platelets
6. Five squares (the same as an erythrocyte count) are (Thrombocytosis) (Thrombocytopenia)

counte on each si e o the hemocytometer. Both si es
o the chamber must be counte . T e total number o Postsplenectomy Aplastic anemia

platelets counte on each si e shoul be within 10 o Polycythemia vera Idiopathic thrombocytopenia
each other. A the total number o platelets counte Chronic myelogenous Acute leukemias

on each si e together an ivi e by 2. T is number rep- leukemia
resents the average number o platelets counte in f ve

squares. Notes

(continued)