Platelet Satellitism Causes a Falsely Decreased Platelet Count
Platelet satellitism most likely causes a falsely decreased platelet count (option A), not a decreased WBC, increased platelet count, or increased WBC count. This phenomenon occurs when platelets adhere to polymorphonuclear neutrophils in EDTA-anticoagulated blood samples, leading to an artificial reduction in the measured platelet count by automated analyzers.
Mechanism of Platelet Satellitism
Platelet satellitism is a rare, in vitro phenomenon characterized by:
- Platelets adhering to polymorphonuclear leukocytes (primarily neutrophils) in a rosette-like formation 1
- Occurs almost exclusively in blood samples collected in EDTA-containing tubes
- Does not occur with other anticoagulants like sodium or lithium heparin 2
- Can be observed through microscopic examination of peripheral blood smears
Laboratory Impact and Clinical Significance
Effect on Platelet Count
- Automated analyzers fail to count platelets attached to neutrophils, resulting in falsely decreased platelet counts 1, 3
- The degree of rosetting can be severe enough to cause significant pseudothrombocytopenia 4
- The estimated frequency of this phenomenon is approximately 0.008% 4
Effect on Other Cell Counts
- Does not significantly affect WBC counts as the neutrophils with attached platelets are still counted as WBCs
- Flow cytometric analysis has shown platelet aggregates predominantly with granulocytes (88.7%), but also with monocytes (5.0%) and lymphocytes (17.0%) 5
Diagnostic Considerations
To identify platelet satellitism and avoid misdiagnosis:
- Examine peripheral blood smears microscopically when unexpected thrombocytopenia is detected 5
- Collect blood in alternative anticoagulants (citrate, heparin) or as capillary blood to confirm true platelet count 2, 4
- Be aware that the phenomenon may persist for weeks after resolution of any underlying condition 2
Pathophysiological Mechanisms
Several mechanisms have been proposed:
- Immunological factors: Formation of antibodies that mediate platelet binding to neutrophil membranes 2
- Presence of certain proteins that attach to platelet surfaces, altering surface charge 3
- Cryofibrinogenemia has been observed in some patients with platelet satellitism 3
Clinical Context
Platelet satellitism has been reported in:
- Healthy individuals during routine check-ups 1
- Patients with infectious diseases 2
- Patients with autoimmune conditions like autoimmune hemolytic anemia 4
The phenomenon is not definitively associated with any specific disease but can lead to important clinical misinterpretations if not properly identified.