TITLE: Hematocrit Determination Using the Micro-Capillary Hematocrit Centrifuge

PRINCIPLE

The hematocrit is the percentage of the total volume of whole blood that is occupied by packed red blood cells when the whole blood is centrifuged at a constant speed for a constant period of time.

Commercial hematology analyzers simplified the process of obtaining a hematocrit by using the following formula when the MCV and RBC of a specimen are known:

HCT = RBCxMCH

10

The hematocrit is elevated in Polycythemia Vera and dehydration. The viscosity of blood increases exponentially at hematocrits of 50% and greater. This results in sluggishness of blood flow and a decrease in oxygen transport. The hematocrit is decreased in primary and secondary anemias.

When performed on body fluids, the spun hematocrit serves as an index of bleeding into the body cavity e.g. peritoneum, chest tube drainage.

PERSONNEL

Medical Technologists and Technicians

SPECIMEN

Patient Preparation:	No special patient preparation by laboratory personnel

Type of Specimen:	K2 EDTA anticoagulated whole blood or free flowing capillary blood. Body fluid specimens.

Handling Precautions:	Handle all specimens using Standard Precautions.

REAGENTS

No reagents necessary

EQUIPMENT

Plain Mylar wrapped micro-hematocrit capillary tubes.

Micro-capillary hematocrit centrifuge (IEC)

Micro-hematocrit capillary tube reader

Clay or suitable sealer

CALIBRATION

See procedure 4840-HE-0550 “Calibration of Micro-centrifuge”. (In Preventive Maintenance Manual).

QUALITY CONTROL

Visually inspect micro-hematocrit tubes for uniformity of the bore size as a means of quality assurance. Record as “QC” on the Manual Hematology Log sheet

Chose a patient sample from the DxH800, LH780 with a normal hematocrit.

Run normal hematocrit patient sample along with current patient specimen.

Result agreement must be within 15% of the automated analyzer.

15% of the analyzer. Record both hematocrits on the Manual Hematology Log sheet

STEPWISE PROCEDURE

Fill 2 Mylar micro-hematocrit capillary tubes with a well-mixed EDTA anticoagulated whole blood.

Seal one end of the tubes with clay. Wipe off the exterior of the tubes.

Place the capillary in the centrifuge with the sealed ends toward the outside. Take care to balance the capillary against the second tube of the same patient or against a balance capillary.

Place the cover on the centrifuge. Close the lid. Turn the centrifuge on by setting the automatic timer to 5* minutes. *Time is dependent of Calibration of Micro-Capillary Hematocrit centrifuge.

Read the percent (%) blood cell volume using the micro-capillary reader.

Place the centrifuged capillary tube in the groove of the indicator so that the bottom of the column of red cells (near the clay) coincides with the black line on the indicator.

Rotate the bottom plate so that the 100 percent line is directly beneath the red line on the indicator. Hold the bottom plate in this position. Using the finger hold, rotate the top place so the spiral line intersects the capillary tube at the plasma-air surface.

Rotate both discs together until the spiral line intersects the capillary tube at the red cell – white cell interface.

Red cell volume in % is read from the point on the scale directly beneath the red line of the indicator.

REPORTING RESULTS

Report results to the nearest whole %.

REFERENCE RANGES

Peripheral Blood:

Males over 12 years – 40 to 50%

Females over 12 years – 30 to 40%

Body Fluids:

No reference range

CALCULATIONS

None

PROCEDURAL NOTES

Routinely hematocrits are reported from the automated analyzers. In the event of their failure the micro-capillary hematocrit result should be used as a check of system versus specimen issue.

REFERENCES

William J. Williams, M.D; Ernest, Bentler, M.D.; Allan J. Erslev, M.D.;R. Wayne Rundles, Ph.D., M.D. Hematology – Second Edition. McGraw-Hill Book Company, A Blakiston Publication (New York, 1977) pp. 240,241, 256,257, and 1622.

Charles E, Seiverd. Hematology for Medical Technologists – Fourth Edition. Lea and Febiger (Philadelphia, 1979) pp.320-330.

William R. Platt, M.D., F.C.A.P., F.A.C.P. Color Atlas and Textbook of Hematology – Second edition. J.B. Lippincott company (Philadelphia, 1979) pp. 75 to 78 and 178 to 180.

Israel Davidsohn, M.D., F.A.C.P., and John Bernard Henry, M.D. Todd-Sanford Clinical Diagnosis by Laboratory Methods – 15th edition. W. B. Saunders Company (Philadelphia, 1974)

S: Lab P&P/Hematology/4840-HE-0220