Thrombocytopenia (including TTP, HIT and ITP): workup and management
Thrombocytopenia (platelets <150,000/µL) in hospital is usually from sepsis, drugs, DIC or dilution, but the dangerous causes are TTP, HIT and DIC. Confirm on a smear, look at timing and the trend, use the 4Ts and PLASMIC scores, and treat the cause.
Working diagnosis
Adult · US guidelines
Draft · awaiting physician review
01Orient
What's new in the evidence
- ISTH 2025 focused update of the 2020 TTP guideline: no change for immune TTP (plasma exchange, steroids, rituximab, caplacizumab); recombinant ADAMTS13 for congenital TTP
- Caplacizumab is continued for 30 days after the last plasma exchange and stopped when ADAMTS13 recovers
- PACER (2023): skipping prophylactic platelet transfusion before CVC placement at platelets 10,000–50,000 led to more bleeding
Differential diagnoses
- Pseudothrombocytopenia (EDTA clumping)
- TTP or HUS (can't miss)
- HIT (can't miss)
- DIC (can't miss)
- Sepsis, drug-induced (linezolid, beta-lactams, vancomycin, TMP-SMX), alcohol, liver disease with splenic sequestration
- ITP, marrow failure, B12/folate deficiency, HELLP or post-transfusion purpura
02Assess
Risk scores and decision tools
- 4Ts score for HIT (≥4 = test and switch anticoagulant)
- PLASMIC score for TTP (6–7 = high probability)
- ISTH DIC score
- Platelet nadir timing relative to heparin or drug exposure
Key history questions
- Heparin exposure in past 100 days and timing of platelet fall
- New drugs in the past 1–2 weeks
- Bleeding, petechiae; thrombosis
- Fever, confusion, kidney injury (TTP/HUS)
- Alcohol, liver disease, recent transfusion, pregnancy
Examination findings
- Petechiae, purpura, mucosal bleeding
- Splenomegaly
- New thrombosis (limb swelling, skin necrosis at heparin sites)
- Neurological signs, fever
03Investigate
Initial investigations
- Repeat count in citrate tube and peripheral smear (schistocytes, clumping)
- CBC, reticulocytes, BMP, LFTs
- PT/INR, aPTT, fibrinogen, D-dimer
- LDH, haptoglobin, bilirubin if hemolysis possible
Advanced investigations
- ADAMTS13 activity and inhibitor (send before plasma exchange)
- PF4/heparin immunoassay, then functional assay (SRA) if positive
- HIV, HCV, H. pylori in suspected ITP; bone marrow if other cytopenias
04Treat
Immediate management
- Suspected TTP: urgent plasma exchange, methylprednisolone or prednisone 1 mg/kg, hematology now; avoid platelet transfusion unless life-threatening bleeding
- Suspected HIT (4Ts ≥4): stop all heparin including flushes, start argatroban, bivalirudin or fondaparinux; no platelet transfusion unless bleeding
- Bleeding with severe thrombocytopenia: platelet transfusion
First-line treatment
- Immune TTP: plasma exchange daily plus steroids, rituximab, and caplacizumab (11 mg IV before first exchange, then 11 mg SC daily)
- HIT: continue non-heparin anticoagulant until platelets recover; then a DOAC or warfarin (start warfarin only after recovery, overlap ≥5 days)
- ITP: treat if platelets <30,000/µL or bleeding (dexamethasone 40 mg daily for 4 days or prednisone 1 mg/kg; IVIG 1 g/kg for rapid rise)
- Prophylactic platelet transfusion threshold: <10,000/µL in stable patients
Second-line treatment
- DIC: treat the cause; replace platelets, fibrinogen and plasma only with bleeding or before procedures
- Drug-induced: stop the drug; platelets usually recover in 5–7 days
Specialist referrals
- Hematology urgently for TTP, HIT or unexplained severe thrombocytopenia
- Apheresis service for plasma exchange
05Disposition
Admission criteria
- Platelets <20,000/µL with bleeding
- Suspected TTP, HIT or DIC
Safe discharge criteria
- Stable count >30,000–50,000/µL without bleeding and cause identified
- Hematology follow-up
Follow-up timing
- CBC within days to 1 week depending on cause
Patient instructions
- Record heparin allergy after HIT
- Avoid NSAIDs and contact sports with low platelets
Monitoring
- Daily CBC during acute management
- ADAMTS13 to guide caplacizumab stop
Clinical pearls and pitfalls
- HIT is a prothrombotic disorder: thrombosis, not bleeding, is the danger
- Platelet transfusion in TTP or HIT can worsen thrombosis
- A 4Ts score ≤3 has a high negative predictive value; avoid unnecessary testing
RefGuidelines and landmark evidence
- GuidelineISTH – Guidelines for Treatment of Thrombotic Thrombocytopenic Purpura (2020)PubMed
- GuidelineASH – Guidelines for Management of VTE: Heparin-Induced Thrombocytopenia (2018)PubMed
- GuidelineASH – Guidelines for Immune Thrombocytopenia (2019)PubMed
- TrialHERCULES: caplacizumab for acquired TTP (2019)PubMed
- TrialPLASMIC score derivation (2017)PubMed
- TrialPACER: platelet transfusion before CVC placement (2023)PubMed
For education only. Typical adult starting points; confirm doses against renal function, allergies, interactions and your institution's protocols. Not a substitute for clinical judgment or senior review.