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Thrombocytopenia

Robert Dunn

Background

  • Platelet count <150k (mild), 50-100k (moderate), <50k (severe)
  • Framework for differential: consumption, sequestration, destruction, production
  • Causes to consider:
    • Can’t Miss Diagnoses: TTP, HUS, HELLP, DIC, HIT
    • Platelet clumping (lab artifact - pseudothrombocytopenia)
    • Splenomegaly can represent: Plt sequestration, cirrhosis, portal hypertension
    • Drug-induced: (Antibiotics, heparin, chemo, GpIIb/IIIa antagonists, H2-antagonists)
    • Rheumatologic cause – SLE, sarcoidosis, scleroderma renal crisis
    • 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) and increased clearance
    • Chronic alcohol use – direct marrow suppression
    • Infections: HIV, HCV, EBV, Parvovirus, Rickettsia, H. pylori, CMV
    • Bone marrow failure: aplastic anemia, MDS, leukemia, chemotherapy
    • Dilutional: fluid resuscitation and massive transfusion

Presentation

  • Petechiae – typically begins distally on lower legs (in mouth = wet purpura), seen when \<10-20k
  • Overt bleeding, mucosal bleeding, epistaxis (seen when \<20k)

Evaluation

  • CMP, CBC w/diff, peripheral smear, citrated platelet count, immature platelet fraction (IPF)
  • LDH, Fibrinogen, d-dimer, PT/aPTT
  • Determine timing of decline as well as prior values
  • 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 (VUMC performs reflexive testing)

Management

  • Plt <50k
    • Discontinue pharmacologic DVT prophylaxis (unless HIT)
    • 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, but if there is active bleeding then consider platelets
      • 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 = concern for TTP
    • Draw ADAMTS13
    • 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) (ACD tube)
Last update: 2022-06-24 23:35:57