Thrombocytopenia

Thrombocytopenia – Robert Dunn

Background

  • Platelet count <150 k/µL (mild), 50-100 k/µL (moderate), <50 k/µL (severe)
  • Framework for differential: Platelet Consumption, sequestration, or destruction
  • Causes to consider:
    • Can’t Miss Diagnoses: TTP, HUS, HELLP, DIC, HIT
    • Splenomegaly can represent: Plt sequestration, cirrhosis, portal hypertension
    • Drug-induced: (Antibiotics, heparin, chemo, GpIIb/IIIa antagonists, H2-antagonists)
    • Rheumatologic cause – SLE and sarcoidosis
    • Sepsis, independent of DIC
    • Immune thrombocytopenia (ITP) is a diagnosis of exclusion
    • Massive physiologic consumption: large hematoma, active hemorrhage
    • Cirrhosis – results in low thrombopoietin (TPO)
    • Chronic alcohol use – direct marrow suppression 
    • Infections: HIV, HCV, EBV, Parvovirus, Rickettsia, H. pylori
    • Bone marrow failure: aplastic anemia, MDS, leukemia, chemotherapy
    • Dilutional: fluid resuscitation and massive transfusion
    • Platelet clumping (lab artifact)

 

 Presentation

  • Petechiae (lower legs typical site; in mouth = wet purpura)
  • Overt bleeding, mucosal bleeding, epistaxis (seen when <20 k/µL ), Splenomegaly

 

Evaluation

  • CMP, CBC w/diff, peripheral smear, citrated platelet count, immature patelet fraction (IPF)
  • LDH, Fibrinogen, PT/aPTT
  • Determine timing of decline
    • Look at other cell lines - never normal to have two cytopenia’s
    • Review recent initiation of drugs: (heparin, antibiotics, and chemotherapy)
  • Consider abdominal ultrasound to look for splenomegaly and liver pathology
  • Infectious work up (HIV, HCV)
  • Calculate 4T Score and consider your pretest probability for HIT testing
    • HIT Ab: ELISA is first test – only run once/day at VUMC so order early if considering
    • Reflex Serotonin release assay (SRA) for confirmation

 

Management

  • Plt <50k
    • Discontinue pharmacologic DVT prophylaxis
    • If on anticoagulation: consider risk/benefits of continued anticoagulation
      • Can transfuse plt’s if AC is mandatory
  • Plt <10k
    • Transfuse platelets given risk of spontaneous intracranial hemorrhage
    • In pt’s with HIT or TTP, there is theoretical concern that transfusing plt can “fuel the fire” and lead to more thrombosis
      • Therefore, bleeding with HIT or TTP, discuss with Hematology before transfusion
  • HIT
    • If pretest probability is high or HIT is confirmed
    • Stop Unfractionated and low molecular weight heparin products
    • Start Argatroban gtt
  • If schistocytes present on peripheral smear = TTP
    • Contact Nephrology and Hematology for PLEX

 

Additional Information

  • Clumping on lab draws:
    • Obtain Citrated platelet (“blue top” tube – CPRS refers to it as a blue top platelet count)
  • If no resolution, obtain a "Gold top" LAB 301 in Epic (Named: Plt count)