Thrombocytopenia¶

Spencer Lessans

Background¶

Classified as either mild (100K-150K), moderate (50K-99K), or severe (<50K)
Can be divided into different causes
- Decreased platelet production
  - Decreased TPO: Cirrhosis
  - Bone marrow suppression: sepsis, EtOH, infections (HIV, tick-borne [RMSF, anaplasma, erhlichia], leptospirosis, parvovirus aplastic crisis), certain drugs (vancomycin, linezolid, bactrim, valganciclovir, immunosuppressive therapies, chemotherapies, allopurinol, colchicine)
  - Bone marrow failure
  - Infiltrative: malignancies (leukemia, lymphoma, myeloma, metastatic solid tumors), infections (TB, NTM, fungal infections), fibrosis (myelofibrosis)
  - Aplastic anemia
  - Nutrient deficiencies: Copper (primary or caused by elevated zinc levels), B12, folate
- Platelet destruction/consumption:
  - Immune thrombocytopenia (ITP):
  - Drug-induced (quinines, sulfonamides, beta-lactams, vancomycin, meropenem, valacyclovir, PPIs, H2 blockers, anti MTB therapy)
  - Heparin-induced thrombocytopenia
  - Infections (HIV, HBV, HCV, CMV, EBV, malaria, H. pylori)
  - Autoimmune disorders (SLE, scleroderma)
  - Thyroid disease
  - Bleeding
  - Idiopathic
  - Thrombotic microangiopathies (TMAs)
  - TTP (acquired, hereditary)
  - HUS
  - DIC (sepsis, APML, pancreatitis, transfusion reaction, HELLP)
  - Drug-induced (Calcineurin inhibitors, gemcitabine, cocaine)
  - Autoimmune (scleroderma renal crisis)
  - Complement-mediated (atypical HUS)
  - Catastrophic antiphospholipid syndrome (APLS)
  - Hypertensive emergency
- Sequestration: Hypersplenism or splenic sequestration (e.g. cirrhosis)
- Pseudothrombocytopenia: platelet clumping
- Dilutional: gestational thrombocytopenia

Presentation¶

Usually asymptomatic
Bleeding due to low platelet counts presents as petechiae
Some causes of thrombocytopenia have a paradoxical increased risk of thrombosis (HIT, DIC, TMA, VITT from the AstraZeneca or Johnson & Johnson COVID vaccines)

Evaluation¶

Repeat CBC w/ diff PLUS a peripheral smear
Citrated platelet count (to rule out pseudothrombocytopenia though a smear without clumping is sufficient to exclude this) and immature platelet fraction (IPF)
IPF can help differentiate between decreased platelet production vs. increased platelet production (in setting of destruction/consumption)
Medication reconciliation to look for any offending drugs
TMA/DIC labs: Haptoglobin, LDH, LFTs, PT/PTT, fibrinogen, peripheral smear
Viral serologies: HIV, HBV, HCV, EBV, CMV, parvovirus (if clinically indicated)
Infectious work-up
Sepsis: blood cultures
Fungal work-up (if clinically indicated): 1,3-Beta-D-Glucan, aspergillus galactomannan, urine blasto Ag, urine and serum histo Ag, crypto Ag
Tick-borne (if clinically indicated): RMSF, Ehrlichia, Anaplasma
Leptospirosis (if clinically indicated)
TB and/or NTM (if clinically indicated): AFB, interferon-Gamma release assay
Autoimmune work-up (if clinically indicated): ESR, CRP, ANA w/ reflex, RF
Nutritional studies: B12, folate, copper, zinc
TSH to screen for thyroid disease
Abdominal U/S to look for splenomegaly (or review recent imaging)
Bone marrow biopsy (if clinically indicated): co-existing cytopenias raise suspicion for bone marrow involvement (particularly if present prior to admission)
HIT work-up: Calculate 4T score: if 4+, order HIT Ab ELISA. If (+), serotonin-release assay (SRA) will reflex for confirmation

Management:¶

Platelet transfusion indications
- CNS or ocular bleeding: <100K
- Pt actively bleeding or plan for OR: <50K
- Plan for central line, bronch, LP, diagnostic endoscopy, or bone marrow biopsy: <20K
- Afebrile, hospitalized pts: <10K
HIT management: Stop any heparin product and start argatroban.
Schistocytes on smear:
- Think TTP or DIC when there are schistocytes on smear and thrombocytopenia
- If DIC is excluded, consult Hematology to discuss sending ADAMTS13 and starting PLEX. A Vascath is needed for PLEX