What platelet count should be reported when the automated cell counter shows 80 x 10^3/μL with platelet satellites around neutrophils, but a sodium citrate tube count is 300 x 10^3/μL?

Reporting Platelet Count in the Presence of Platelet Satellites

The platelet count of 300 x 10³/μL from the sodium citrate tube should be reported (answer B), as this represents the true platelet count when EDTA-induced platelet clumping is present.

Understanding Platelet Satellite Phenomenon

When platelet satellites are observed around neutrophils on a blood smear, this indicates EDTA-induced pseudothrombocytopenia, a common laboratory artifact that causes falsely low platelet counts. This phenomenon occurs due to:

• Antiplatelet antibodies that cause platelets to clump or adhere to white blood cells in the presence of EDTA
• The automated cell counter incorrectly counts these clumped platelets, resulting in a falsely low count (80 x 10³/μL in this case)
• The presence of platelet satellites around neutrophils is a classic microscopic finding confirming this artifact

Correct Laboratory Approach

When pseudothrombocytopenia is suspected, the following steps should be taken:

1. Confirm the presence of platelet clumping or satellites microscopically
2. Collect a sample in an alternative anticoagulant (sodium citrate)
3. Analyze the citrated sample for a more accurate platelet count
4. Report the citrated tube result as the true platelet count

The sodium citrate tube prevents the antibody-mediated platelet clumping that occurs with EDTA, providing a more accurate assessment of the patient's true platelet count.

Why Not Other Options?

• Option A (estimated count from blood smear): While blood smear estimates can be helpful, they are less accurate than automated counts from properly anticoagulated samples 1. When a reliable automated count is available from a citrate tube, it should be used.

• Option C (330): This would represent a mathematical correction of the citrate tube result (multiplying by 1.1 to account for the dilution effect of citrate). However, this correction is not necessary for clinical decision-making and may introduce additional error 2.

• Option D (80): This is the falsely low count from the EDTA tube affected by platelet clumping and should not be reported as it does not reflect the patient's true platelet status.

Clinical Implications

Reporting the correct platelet count is critical for patient care as:

• Falsely low platelet counts may lead to unnecessary:

  • Platelet transfusions
  • Postponement of procedures
  • Additional diagnostic workup for thrombocytopenia

• A platelet count of 300 x 10³/μL is within normal range and would not require any intervention, whereas a count of 80 x 10³/μL might trigger unnecessary clinical concern or interventions

Laboratory Best Practices

• Always examine blood smears when automated platelet counts are unexpectedly low
• Document the presence of platelet clumping or satellites when observed
• Use alternative anticoagulants (sodium citrate) when EDTA-induced pseudothrombocytopenia is suspected
• Clearly communicate to clinicians when pseudothrombocytopenia is identified to prevent misdiagnosis

By reporting the sodium citrate tube result of 300 x 10³/μL, the laboratory provides the most accurate information for clinical decision-making.