Peripheral smear CP call thread #4: thrombocytopenia / platelet count verification
#hemepath
#hemepath
For patients with confirmed thrombocytopenia, many key features to look for have been described in previous threads. Look for signs of MAHA (schistocytes), dysplastic granulocytes or other abnormal WBCs. In this thread, I’ll focus more on potential pitfalls with platelet counts.
Most hematology analyzers use impedance as the primary method for determining platelet counts - so any platelet-sized particle will be included in the count, and large platelets or platelet clumps may not be classified as platelets.
Some analyzers include a secondary method (fluorescent optical or immunological) to confirm low or flagged platelet counts.
As with any lab test, preanalytical factors can lead to inaccurate results. Undetected microclots can cause falsely low platelet counts. Check the slide edges carefully for fibrin strands.
Platelet satellitism/satellitosis is an in vitro phenomenon thought to be mediated by EDTA-dependent antibodies against platelet glycoproteins and neutrophil Fc receptors. The platelets that are stuck to neutrophils will not be counted by the analyzer.
EDTA-dependent platelet clumping is an in vitro phenomenon associated with antibodies against platelet glycoproteins. Platelets in clumps aren’t counted as individual platelets, leading to pseudothrombocytopenia. Suboptimal phlebotomy technique can also cause platelet clumping.
EDTA-dependent clumping/satellitism may be prevented by collecting a sample in an alternative anticoagulant, such as sodium citrate.
RBC or WBC fragments may be counted as platelets and falsely elevate the platelet count. Note the presence of platelet-sized blast fragments in this patient with AML.
This patient has occasional microspherocytes (black arrow) and circulating yeast forms (blue arrow) in the peripheral blood. The presence of these platelet-sized particles in the blood can lead to a falsely elevated automated platelet count.
Cryoglobulins are immunoglobulins that precipitate in cool temps, seen in association with autoimmune, infectious or lymphoproliferative diseases. The precipitated proteins can interfere with automated cell counts, and may be counted as platelets or WBCs depending on their size.
If you’ve ruled out pseudothrombocytopenia and you don’t see any obvious cause of thrombocytopenia on the smear, reporting pertinent negatives is still helpful. Hypersplenism, medication effect, infection, and ITP may be considered in the DDx.
جاري تحميل الاقتراحات...