Platelet Variants

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Large Platelets
Abnormal Platelet Morphology
Agranular and Hypogranular Platelets
Platelet Clumps
Platelet Satellitosis
Platelet on Red Blood Cell

Platelet Variants.png

Large Platelets

Increased platelet size should be noted. Reporting will vary from lab to lab. Some labs differentiate Macro Platelets (slightly large to approaching the size of a RBC) versus Giant Platelets (size of a RBC and larger).

Macro Platelet \(\PageIndex{}\)

Giant Platelet \(\PageIndex{}\)

Abnormal Platelet Morphology

Normal platelets are discoid in shape. More than an occasional abnormally shaped platelet should be noted. Abnormal platelet shapes may interfere with normal platelet function.

Abnormal Platelet Morph \(\PageIndex{}\)

Agranular and Hypogranular Platelets

Normal platelets have fine granules dispersed throughout the cell. Occasionally they are more densely concentrated in one area. Platelets that have decreased or missing granules should be noted. Platelet granules are vital to normal platelet function.

Abnormal Platelet Granulation\(\PageIndex{}\)

Platelet Clumps

Platelet clumping can be induced by EDTA anticoagulant. EDTA causes a conformational change in the platelets resulting in platelet agglutination. This may result in a falsely decreased platelet count and a falsely increased white blood cell count. It is also difficult to obtain an accurate platelet estimate.

To resolve this problem, the specimen can be redrawn in a sodium citrate tube. The sample is analyzed by the hematology instrument. The WBC and Platelet count must be corrected for the increased dilution in a sodium citrate tube by multiplying the counts by 1.1. All other CBC parameters should be reported from the EDTA tube.

Platelet clumps on the peripheral blood smear may also indicate that clotting has been initiated and the specimen should be checked for clots.

Platelet Clumping \(\PageIndex{}\)

Platelet Satellitosis

Some samples experience an invitro phenomenon where EDTA causes the platelets to surround the neutrophils. The mechanism is not well understood, but there is some evidence an autoantibody is involved. EDTA may cause an alteration in platelet and neutrophil membranes that allow the antibody to form a bridge between the cells.

Platelet Satellites \(\PageIndex{}\)

Platelet on Red Blood Cell

It is not uncommon to observe a platelet sitting on top of a red blood cell. There is no clinical significance and should not be noted. However, you must be careful not to confuse this with a red blood cell inclusion. If the platelet is on top of the red blood cell, there will usually be a clear area around it as the platelet pushes some of the hemoglobin aside. If the object is a true inclusion inside the red blood cell, there will be no clear area.

Platelet on RBC \(\PageIndex{1}\)