Differential diagnosis:
(1) clumped platelets
(2) stain debris
(3) cryoglobulins
(4) cryofibrinogen
Features of clumped platelets:
(1) granules present in the masses
(2) platelet count from automated analyzer reports thrombocytopenia
(3) often associated with EDTA anticoagulant, absent with citrate
Stain debris:
(1) platelet and leukocyte counts normal
(2) dark granules, often with sharp edges
(3) absent in repeat smear stain in fresh, filtered stain
Cryoglobulin:
(1) leukocyte count from automated counter significantly higher than the estimate from the blood smear
(2) associated with cold (winter or refrigerated specimen); absent in repeat specimen collected in citrate and kept at 37°C
(3) presence of monoclonal proteins on serum protein electropheresis
(4) history of infection, autoimmune disease, lymphoproliferative disease
Cryofibrinogen:
(1) abnormal thrombin time
(2) associated with cold (winter or refrigerated specimen); absent in repeat specimen collected in citrate and kept at 37°C
(3) leukocyte count from automated counter significantly higher than the estimate from the blood smear
(4) history of autoimmune or malignant disease
Need to confirm: The presence of protein precipitates in specimens collected in heparin due to formation of heparin-protein complexes.
