CBC – Platelet Count Drop

ABCs and Vitals

  • If unstable -> call for assistance
  • Review previous CBCs to assess platelet trends
  • Send an urgent CBC with blood film:
    • If platelet clumping/aggregation -> repeat in a citrate tube
    • If large platelets -> repeat with a manual count
  • Can’t miss – Thrombotic microangiopathies such as TTP or drug-induced thrombotic microangiopathy; syndromes with thrombosis (HIT, DIC, APS, CAPS, or acute promyelocytic leukemia); TA-GVHD.

HPI

  • Mucocutaneous bleeding e.g., epistaxis, gum bleeding, menorrhagia, hematuria, melena, hematochezia
  • Bleeding from any orifices, easy bruising, rash (purpura, petechiae, ecchymosis)
  • Fever or neurological deficits
  • History of
    • Previous bleeding episodes or platelet transfusion.
    • Liver disease, autoimmune disease, VTEs, sepsis, malignancy.
  • Dietary habits e.g., veganism, alcoholism
  • Medications, e.g., antiplatelets, anticoagulants, LMWH, antibiotics like linezolid, vancomycin, tazocin
  • Review the patient file to determine if investigations are ongoing

Common Causes of Thrombocytopenia

Immune-mediated
  • Primary immune thrombocytopenia (ITP)
  • Drug-induced: heparin, vancomycin, sulfonamides, NSAIDs, antibiotics, antiplatelets
Infections
  • HIV, Hepatitis C, EBV, H. pylori
  • Sepsis with DIC
  • Malaria, Babesia (intracellular parasites)
Food & Beverages
  • Quinine-containing drinks (tonic water)
  • Walnuts, herbal teas
Other Common Causes
  • Hypersplenism (e.g., liver disease)
  • Alcohol use
  • Nutrient deficiencies: B12, folate, copper
  • Autoimmune diseases: SLE, RA
Pregnancy-related
  • Gestational thrombocytopenia
  • Preeclampsia, HELLP syndrome
Bone Marrow & Malignancy
  • Myelodysplasia
  • Bone marrow infiltration/suppression (e.g., leukemia, lymphoma)
  • Cancer with DIC
Other Hematologic Causes
  • Paroxysmal nocturnal hemoglobinuria (PNH)
  • Thrombotic microangiopathies (TTP, HUS, drug-induced)
  • Antiphospholipid syndrome (APS)
  • Aplastic anemia
  • Hereditary thrombocytopenias

EXAMINATION

  • Skin & Mucosal Bleeding
    • Petechiae, purpura, ecchymoses
    • Mucosal bleeding e.g., gums, nose, GI tract
  • Assess Liver & Spleen
  • Examine lymph nodes

Skin Bleeding Tips

Petechiae
  • Pinpoint, flat, red lesions that appear in crops
  • Caused by RBC leakage from capillaries
  • Non-blanching, asymptomatic, and non-palpable
  • Most dense in dependent areas:
    • Feet and ankles (ambulatory)
    • Presacral area (bedridden)
  • Not found on soles due to thicker subcutaneous protection
  • Seen commonly in immune thrombocytopenia (ITP)
Purpura
  • Purplish discoloration from confluent petechiae
  • Dry purpura: skin
  • Wet purpura: mucosal surfaces (e.g., gums)
  • Wet purpura = possible predictor of severe hemorrhage
  • Palpable purpura suggests vasculitis or vascular inflammation (not typical of thrombocytopenia)
Ecchymoses
  • Nontender bruises in skin layers
  • Color changes over time: red/purple → green/yellow due to heme breakdown
  • Usually small, multiple, superficial
  • Can appear without obvious trauma
  • Do not spread into deep tissues
  • Mark with pen to track changes or new bleeds

MANAGEMENT

  • Monitor for any bleeding
  • If clumping/aggregation -> repeat CBC in citrate tube
  • If large platelets -> repeat with a manual count
  • Send
    • Blood film, CBC, coagulation profile, LFT, RFT
    • If on LMWH, calculate the 4Ts score to assess HIT risk
    • Plasmic score for TTP
  • Platelet transfusion
    • If bleeding and platelets < 50,000: transfuse 1 unit IV and repeat as needed
    • If platelets < 10,000: transfuse 1 unit IV regardless of bleeding, repeat as needed
  • LMWH Management:
    • Do not stop prophylactic LMWH if platelets > 30,000 and no HIT suspicion
    • Do not stop therapeutic LMWH if platelets > 50,000
    • Stop LMWH and use pneumatic compression if platelets < 30,000
  • New onset thrombocytopenia workup (if cause not obvious)
    • Virology HBsAg, HCV Ab and HIV Ag/Ab
    • Iron profile, Vitamin B12, Folate and Copper
    • If Hb drop -> hemolytic workup (Reticulocytes, LDH, Haptoglobin, LFT)

ESCALATION

  • Call for assistance based on findings or if platelet count remains critically low
  • Consult seniors and/or hematology for further management as needed
MOC