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Thrombotic Thrombocytopenic Purpura Management (ISTH 2025)

Thrombotic Thrombocytopenic Purpura Management (ISTH 2025): Suspected TTP → Suspected TTP is an emergency: call haematology now → Urgent tests → Calcula...

Pathway Overview

15 steps

Algorithm Steps

15 total

  1. 01Start

    Suspected TTP

    Thrombocytopenia and microangiopathic haemolytic anaemia (MAHA) without another clear cause

  2. 02Warning

    Suspected TTP is an emergency: call haematology now

    Arrange transfer to a centre with plasma exchange and ICU. No plasma exchange on site: start corticosteroids; haematology may advise plasma infusion (FFP) while waiting; do not delay transfer. Do not wait for the classic pentad (present in only about 40%).

    • Take blood for ADAMTS13 activity and inhibitor before plasma exchange or any blood product
    • Avoid platelet transfusion unless serious bleeding or a high-bleeding-risk procedure (haematology decides); do not delay plasma exchange for it
    • Pregnant or postpartum: TTP, aHUS and HELLP overlap; joint haematology and obstetric care
  3. 03Action

    Urgent tests

    Confirm MAHA and look for other causes

    • FBC, reticulocytes and blood film (schistocytes)
    • LDH, haptoglobin, bilirubin (indirect), direct antiglobulin test (negative in TTP)
    • UEC and creatinine, LFTs, urinalysis; PT/INR, APTT, fibrinogen (usually near normal in TTP)
    • Troponin and ECG; CT or MRI brain if neurological signs
    • ADAMTS13 activity and inhibitor (anti-ADAMTS13 IgG) before plasma
    • Pregnancy test (beta-hCG); HIV, hepatitis B and C serology
    • Diarrhoea: stool Shiga toxin or STEC PCR and culture
  4. 04Action

    Calculate PLASMIC score (adults)

    Estimates the chance of ADAMTS13 below 10%. Not validated in children.

    • Platelets below 30 x10^9/L (+1)
    • Haemolysis: reticulocytes above 2.5%, undetectable haptoglobin or indirect bilirubin above 34 micromol/L (2 mg/dL) (+1)
    • No active cancer in the past year (+1)
    • No solid-organ or stem cell transplant (+1)
    • MCV below 90 fL (+1)
    • INR below 1.5 (+1)
    • Creatinine below 177 micromol/L (2.0 mg/dL) (+1)
  5. 05Decision

    PLASMIC score result

    0-4 low, 5 intermediate, 6-7 high chance of TTP

  6. 6-7
  7. 06Warning

    PLASMIC 6-7: high chance of TTP (62-82%)

    Treat as TTP now. Do not wait for ADAMTS13.

  8. 07Action

    Start TTP treatment: PLASMIC 5-7 or high clinical suspicion

    Daily plasma exchange with corticosteroids, started as soon as possible

    • Plasma exchange: 1-1.5 plasma volumes (40-60 mL/kg) daily until platelet count and LDH are normal
    • Corticosteroids with plasma exchange (adult): e.g. methylprednisolone 125 mg IV 2-4 times daily; haematology sets the oral taper
    • Caplacizumab only if high suspicion and the ADAMTS13 result is expected within 72 h (adult, or age 12 or more and 40 kg or more); hold if active bleeding
    • Caplacizumab dose (EU label): 10 mg IV before the first plasma exchange, then 10 mg subcut daily after each exchange (US label: 11 mg)
    • Caplacizumab: careful review with anticoagulants, antiplatelets or thrombolysis; withhold 7 days before elective procedures; no data in pregnancy
    • Known or suspected congenital TTP: plasma infusion 10-15 mL/kg daily until symptoms resolve, or recombinant ADAMTS13; no immunosuppression or caplacizumab
    • VTE prophylaxis: mechanical while platelets below 50 x10^9/L; consider prophylactic LMWH once above 50 x10^9/L
    • ICU-level monitoring of neurological and cardiac status; repeat troponin
  9. 08Decision

    ADAMTS13 activity result

    Below 10% confirms TTP; 10-20% is equivocal; above 20% makes TTP unlikely

  10. <10%
  11. 09Action

    ADAMTS13 below 10%: TTP confirmed

    Continue full treatment

    • Continue daily plasma exchange until platelet count and LDH are normal
    • Immune TTP (inhibitor or anti-ADAMTS13 IgG present): add rituximab 375 mg/m2 IV weekly for 4 doses (adult) as early as possible; screen for hepatitis B first
    • Caplacizumab (if started): continue daily for 30 days after the last plasma exchange; longer if ADAMTS13 stays low, with immunosuppression optimised
    • Taper corticosteroids over about 3 weeks once the platelet count is stable
    • No inhibitor, or onset in childhood or pregnancy: test for congenital TTP (haematology)
  12. Response
  13. 10Outcome

    Response: remission and follow-up

    Platelet count and LDH normal. Check ADAMTS13 monthly for 3 months, then every 3 months for the first year, then every 6-12 months.

    • ADAMTS13 below 10% in remission: haematology may give pre-emptive rituximab
    • Watch for mood, memory problems and hypertension
  14. No response
  15. 11Outcome

    No response: refractory TTP (platelets not rising after 3-4 days)

    Haematology-led escalation: higher-dose corticosteroids; rituximab and caplacizumab if not given. Other options (e.g. cyclophosphamide, vincristine, ciclosporin, splenectomy) have little evidence.

  16. 10-20%
  17. 12Action

    ADAMTS13 10-20%: equivocal result

    Haematology decides whether to continue plasma exchange, corticosteroids, rituximab and caplacizumab

    • Repeat ADAMTS13 and review for other causes of TMA
  18. >20%
  19. 13Action

    ADAMTS13 above 20%: TTP unlikely

    Look for another cause of TMA with haematology

    • Stop caplacizumab; haematology decides when to stop plasma exchange
    • Consider aHUS (complement inhibitor after meningococcal vaccination; nephrology), STEC-HUS, drug-induced TMA, malignant hypertension, HELLP, cancer or transplant-associated TMA
    • See the thrombotic microangiopathy (TTP, HUS, aHUS) pathway
  20. 5
  21. 14Action

    PLASMIC 5: intermediate (5-24% chance)

    Send ADAMTS13 urgently. Start plasma exchange and corticosteroids while waiting.

    • Do not start caplacizumab until ADAMTS13 is below 10%
    • Review daily with haematology
  22. Path rejoins step 07Shared downstream outcome
  23. 0-4
  24. 15Action

    PLASMIC 0-4: TTP unlikely (0-4% chance)

    Look for another cause. Treat as TTP if clinical suspicion stays high.

    • Other causes: STEC-HUS (bloody diarrhoea), aHUS, DIC, sepsis, HELLP or pre-eclampsia, drugs, malignant hypertension, cancer, transplant
    • Still send ADAMTS13
    • High clinical suspicion despite the score: start TTP treatment (next steps)
  25. Path rejoins step 07Shared downstream outcome

Guideline Source

2025 focused update of the 2020 ISTH guidelines for management of thrombotic thrombocytopenic purpura

DOI: 10.1016/j.jtha.2025.06.002View Guideline

Clinical Safety Information

Clinical Decision Support — Not a Substitute for Clinical Judgment

Individual patient factors may require deviation from these recommendations.

Known Limitations

  • Caplacizumab is not on the ARTG: access in Australia is through the TGA Special Access Scheme
  • PLASMIC score is validated in adults only and does not replace clinical judgement
  • ADAMTS13 results can take days; treatment often starts before the diagnosis is certain
  • Congenital TTP and TTP in pregnancy need specialist plans beyond this pathway

Applicable Regions

AUUSEUGlobal

AU: Caplacizumab is not on the ARTG (search 28 Sep 2026); access through the TGA Special Access Scheme. Recombinant ADAMTS13 (Adzynma) is on the ARTG. Labs report creatinine and bilirubin in micromol/L.

EU: Caplacizumab EMA-approved for immune TTP; label dose 10 mg.

US: Caplacizumab FDA-approved for immune TTP; label dose 11 mg.

Version 2Next review: 2027-09-30

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Frequently Asked Questions

What is the Thrombotic Thrombocytopenic Purpura Management (ISTH 2025)?

The Thrombotic Thrombocytopenic Purpura Management (ISTH 2025) is a emergency clinical algorithm for Hematology & Oncology. It provides a structured decision tree to guide clinical decision-making, based on 2025 focused update of the 2020 ISTH guidelines for management of thrombotic thrombocytopenic purpura.

What guideline is the Thrombotic Thrombocytopenic Purpura Management (ISTH 2025) based on?

This algorithm is based on 2025 focused update of the 2020 ISTH guidelines for management of thrombotic thrombocytopenic purpura (DOI: 10.1016/j.jtha.2025.06.002).

What are the limitations of the Thrombotic Thrombocytopenic Purpura Management (ISTH 2025)?

Known limitations include: Caplacizumab is not on the ARTG: access in Australia is through the TGA Special Access Scheme; PLASMIC score is validated in adults only and does not replace clinical judgement; ADAMTS13 results can take days; treatment often starts before the diagnosis is certain; Congenital TTP and TTP in pregnancy need specialist plans beyond this pathway. Individual patient factors may require deviation from these recommendations.

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