TTP Clinical Guidance
A cleaner, practical pathway for recognizing suspected thrombotic thrombocytopenic purpura, obtaining ADAMTS13 testing, initiating time-sensitive management, and supporting patients through remission and long-term follow-up.
Recognize
Look for thrombocytopenia plus microangiopathic hemolytic anemia and assess whether TTP could explain the picture.
Draw ADAMTS13
Obtain the sample before plasma therapy or other plasma exposure whenever feasible.
Treat urgently
When suspicion is high, management may need to begin before the ADAMTS13 result is back.
Monitor recovery
Clinical recovery and ADAMTS13 recovery are related but distinct; both shape follow-up decisions.
When should TTP be considered?
TTP should be considered in patients with thrombocytopenia and microangiopathic hemolytic anemia, particularly when another explanation is not immediately clear. Neurologic, cardiac, renal, gastrointestinal, or other organ involvement may occur, but the presentation is variable.
Because TTP can deteriorate rapidly, the goal is not to wait for a complete classic presentation. Evaluate the overall TMA picture and move quickly to ADAMTS13 testing and specialist involvement.
What tests should be obtained when TTP is suspected?
The 2020 ISTH Good Practice Statements describe an initial laboratory and organ-injury assessment for presumptive TTP. ADAMTS13 should be drawn before therapeutic plasma exchange or other plasma exposure whenever feasible.
| Test / assessment | Role in initial evaluation | Frequency stated by ISTH GPS |
|---|---|---|
| CBC + platelet count | Identify thrombocytopenia and establish a baseline for subsequent response. | Initial evaluation; ongoing trend during the acute episode is clinically required, but the GPS does not assign a universal lab interval. |
| Peripheral blood film | Review for fragmented red cells / schistocytes. | Initial evaluation; repeat when clinically needed. |
| LDH | Supports assessment of microangiopathic hemolysis and treatment response. | Initial evaluation; TPE is generally continued every 24 hours until platelet count and LDH normalize. |
| Creatinine | Assess renal involvement and help evaluate the broader TMA differential. | Initial evaluation; subsequent testing according to clinical course. |
| Hemolysis studies | Haptoglobin and indirect bilirubin help demonstrate hemolysis; reticulocytes are commonly included in the clinical workup. | Initial evaluation; trend as clinically indicated. |
| Coagulation testing | Usually relatively normal in TTP and may help identify competing processes such as DIC. | Initial evaluation; repeat if clinically indicated. |
| Direct antiglobulin (Coombs) test | Expected to be negative in TTP; helps distinguish autoimmune hemolytic anemia. | Initial differential evaluation. |
| Troponin I + ECG | Screen for subclinical cardiac involvement. | Troponin at diagnosis, followed by serial troponin; ECG and echocardiography as clinically indicated. |
| Brain CT / MRI | Evaluate suspected neurologic injury. | Symptom- or sign-driven, not routine at a fixed interval. |
| ADAMTS13 activity + inhibitor and/or anti-ADAMTS13 IgG | Central to confirming TTP and distinguishing immune-mediated disease. | Draw before TPE/plasma exposure whenever possible. In remission, measure serially at follow-up if available. |
Obtain the sample before plasma therapy whenever possible.
Draw ADAMTS13
Obtain plasma for ADAMTS13 activity and, where available, inhibitor or anti-ADAMTS13 antibody testing before therapeutic plasma exchange or other plasma exposure.
Estimate probability
Use clinical judgment and a validated prediction tool such as the PLASMIC score when appropriate. Prediction tools support—but do not replace—clinical assessment.
Do not wait when suspicion is high
For a high pretest probability of iTTP, management may need to begin before the ADAMTS13 result returns.
Interpret in context
Severe ADAMTS13 deficiency (<10% activity) strongly supports TTP. Borderline or higher activity should prompt careful reassessment for other TMA syndromes and causes.
FAST4TMA helps eligible patients with suspected TMA and their clinicians navigate testing access, collection options, and laboratory logistics. It may also support clinically appropriate monitoring.
Modern iTTP care is multimodal.
The 2025 ISTH focused update maintained the direction and strength of the 2020 iTTP treatment recommendations. Core acute management is built around rapidly controlling microvascular thrombosis while suppressing the autoimmune process.
Therapeutic plasma exchange
Remains a foundational component of acute iTTP treatment in current ISTH guidance.
Corticosteroids
ISTH recommends corticosteroids in addition to plasma exchange for a first acute iTTP event.
Caplacizumab
ISTH conditionally suggests caplacizumab for acute iTTP, including first events and relapses. Patient-specific bleeding risk and local treatment pathways remain important.
Rituximab / immunosuppression
Rituximab is incorporated into contemporary iTTP management as immunomodulatory therapy, with treatment decisions individualized to the clinical setting.
A practical schedule drawn from the ISTH Good Practice Statements.
Acute hospitalization
Continuous / serialFor unstable acute TTP, the GPS supports continuous neurologic, cardiac and oxygen-saturation monitoring. Troponin is measured at diagnosis and serially thereafter; ECG and echocardiography are used as clinically indicated.
First 3 months after remission
Every monthPatients are typically assessed monthly. If available, ADAMTS13 activity is usually measured at each follow-up assessment and more often if it begins to fall.
Remainder of first year
Every 3 monthsContinue clinical follow-up and serial ADAMTS13 measurement when available.
Stable after year 1
Every 6–12 monthsThe GPS describes extending follow-up to every 6–12 months when stable, with additional testing if symptoms or the ADAMTS13 trajectory warrant it.
If ADAMTS13 begins to fall
More frequentlyThe GPS specifically recommends more frequent ADAMTS13 measurement when levels begin to drop. Persistently severe deficiency (<10%) is associated with relapse risk.
Long-term survivorship
Serial follow-upRoutine follow-up should also consider hypertension, mood disorders and neurocognitive symptoms; the GPS does not specify a universal screening interval for these complications.
Clinical response is not the same as ADAMTS13 recovery.
Anti-VWF therapy changed the relationship between platelet recovery and underlying autoimmune disease activity. International consensus definitions therefore distinguish clinical response/remission and clinical relapse from ADAMTS13 remission/relapse.
Follow clinical recovery
Platelets, hemolysis, symptoms and organ injury remain essential to assessing the acute episode.
Follow ADAMTS13
Persistent severe deficiency can remain clinically important even after platelet recovery and should inform specialist follow-up.
Watch for recurrence
New symptoms or laboratory evidence suggesting recurrent TMA require urgent reassessment rather than routine outpatient follow-up.
Remission is an active phase of care.
Follow-up after an acute episode should include clinical assessment and serial ADAMTS13 monitoring according to the treating specialist's plan. ISTH guidance conditionally supports prophylactic rituximab for patients in remission who have persistently low ADAMTS13 activity without clinical signs or symptoms.
The frequency of monitoring and threshold for intervention should be individualized based on prior disease course, ADAMTS13 trajectory, treatment history, comorbidities, pregnancy plans, and access to specialist care.
Pregnancy requires closer, specialist-led monitoring.
The ISTH Good Practice Statements support joint care with hematology and maternal-fetal medicine/perinatology for patients with a history of TTP.
CBC
At least monthly during pregnancy.
ADAMTS13
Monthly or at least every 2–3 months, with more frequent monitoring if activity begins to fall.
Pregnancy + postpartum
ADAMTS13 activity should be monitored throughout pregnancy and during the postpartum period.
Surviving the acute episode does not always mean recovery is complete.
Evidence increasingly recognizes long-term morbidity after iTTP, including cardiovascular events, neurocognitive concerns, mood symptoms, fatigue, and higher long-term mortality in some cohorts. Follow-up should therefore extend beyond platelet counts alone.
Cardiovascular health
Address hypertension and traditional cardiovascular risk factors and maintain a low threshold to evaluate concerning neurologic or cardiac symptoms.
Brain & cognition
Ask about memory, concentration, headaches and return to work or school; consider further evaluation when symptoms persist.
Mental health & fatigue
Screen for depression, anxiety, post-traumatic stress, sleep disturbance and persistent fatigue when clinically appropriate.
Continuity
Provide a clear relapse plan and maintain connection with a clinician or center experienced in TTP.
cTTP now has a distinct replacement-therapy pathway.
The 2025 ISTH focused update added a strong recommendation favoring recombinant ADAMTS13 over plasma infusion for patients with cTTP in remission when recombinant ADAMTS13 is available. When it is not available or accessible, plasma infusion remains an option and shared decision-making is emphasized.
Pregnancy, acute illness, procedures, and other stressors may require individualized management by clinicians experienced in cTTP.
Built around guidelines and contemporary evidence.
ISTH treatment guideline — 2025 focused update
Maintains the 2020 iTTP recommendations and updates cTTP recommendations for recombinant ADAMTS13.
PubMed →ISTH diagnostic guideline
ADAMTS13-centered diagnostic strategy, including sampling before plasma therapy and use of pretest probability.
Read guideline →International Working Group outcome definitions
Distinguishes clinical remission/relapse from ADAMTS13 remission/relapse in the modern treatment era.
Find publication →USTMA publications
Explore registry analyses, survivorship work, rapid-testing initiatives and other USTMA-affiliated scientific output.
Browse USTMA publications →Content is intended for clinician education and decision support and does not replace individualized medical judgment, institutional protocols, current prescribing information, or emergency evaluation.