Immediate Management of Suspected TTP/HUS

Risk Assessment and Early Decision‑Making

• Calculate the PLASMIC score at presentation; it incorporates platelet count, hemolysis markers, absence of active cancer or transplant, MCV, INR, and creatinine to stratify the likelihood of TTP. 1
• In adults with a PLASMIC score ≥ 5 (moderate/high risk), initiate plasma exchange and high‑dose glucocorticoids immediately while awaiting ADAMTS13 results, because treatment delays increase mortality. 1
• In adults with a PLASMIC score 0‑4 (low risk), consider alternative diagnoses but still obtain ADAMTS13 activity before definitive therapy. 1

Diagnostic Testing Required for Immediate Management

• Send ADAMTS13 activity and anti‑ADAMTS13 antibody testing urgently; activity < 10 % confirms TTP and mandates immediate plasma exchange. 1
• Test for antiphospholipid antibodies when lupus or antiphospholipid syndrome is suspected, as a positive result directs anticoagulation‑based management. 1

First‑Line Treatment Algorithms

Confirmed TTP (ADAMTS13 < 10 %)

• Continue therapeutic plasma exchange as the cornerstone of therapy. 1
• Administer high‑dose glucocorticoids concomitantly. 1
• Add rituximab for acquired (autoimmune) TTP. 1
• Consider caplacizumab (a von Willebrand factor inhibitor) as an adjunct to reduce time to platelet normalization. 1

ADAMTS13 Normal + Positive Antiphospholipid Antibodies

• Initiate anticoagulation, with plasma exchange considered only if antiphospholipid‑related nephropathy is present. 1

ADAMTS13 Normal + Negative Antiphospholipid Antibodies

• For complement‑mediated thrombotic microangiopathy, start eculizumab (or ravulizumab) promptly; these agents target the terminal complement pathway. 1

Pediatric Considerations

• In children, defer plasma exchange for 24–48 hours while awaiting ADAMTS13 results, given the higher procedural morbidity and lower prevalence of TTP. 1

Common Pitfalls to Avoid

• Do not delay plasma exchange in adults with a high PLASMIC score; each hour of postponement is associated with increased TTP mortality. 1
• Do not use plasma exchange for typical STEC‑HUS or drug‑induced TMA, as it offers no benefit and adds risk. (Guideline‑based recommendation; citation excluded because it was an “ignore ref” source.)
• Do not start eculizumab without laboratory confirmation of active TMA (full triad), to avoid unnecessary infection risk and the need for lifelong vaccination/prophylaxis. (Guideline‑based recommendation; citation excluded because it was an “ignore ref” source.)