Statistical & Clinical Analysis
PLASMIC Score Formula: Severe ADAMTS13 Deficiency & Emergent TTP Triage (0 to 7)
Identify immune Thrombotic Thrombocytopenic Purpura (ADAMTS13 <= 10%) within minutes of admission Labs using Pavan Bendapudi’s 7-point PLASMIC score for life-saving therapeutic plasma exchange (TPE) & caplacizumab.
Why send-out ADAMTS13 assays take days—and how PLASMIC >= 6 guides immediate life-saving plasma exchange!
Untreated immune Thrombotic Thrombocytopenic Purpura (iTTP) carries > 90% mortality, yet send-out ADAMTS13 activity assays often take 24–72 hours while sepsis DIC, HUS, or transplant TMA mimic schistocytic microangiopathic hemolytic anemia (MAHA)! Pavan K. Bendapudi et al. (2017, The Lancet Haematology — Harvard TMA Research Collaborative, c-statistic 0.96, ISTH TTP Guideline endorsed) built the 0–7 PLASMIC score for patients with MAHA (schistocytes) + thrombocytopenia:
+1 point each for: (P) Platelet count < 30 × 10^9/L, (L) combined hemoLysis variable (reticulocyte > 2.5%, undetectable haptoglobin, OR indirect bilirubin > 2.0 mg/dL), (A) no Active cancer in past year, (S) no history of Solid-organ or stem-cell transplant, (M) MCV < 90 fL, (I) INR < 1.5, and (C) Creatinine < 2.0 mg/dL! PLASMIC 0–4 carries < 4% risk of severe ADAMTS13 deficiency, 5 is intermediate (~6–24%), and PLASMIC 6–7 carries 62–82% probability—mandating emergent Therapeutic Plasma Exchange + corticosteroids!
| PLASMIC Score (0–7, Requires Schistocytic MAHA) | Probability of ADAMTS13 <= 10% | ISTH Emergent Management Pathway |
|---|---|---|
| PLASMIC 0–4 (Low Risk) | 0%–4% Risk | Evaluate Alternative TMA (HUS, DIC, Drug/Transplant TMA) |
| PLASMIC 5 (Intermediate Risk) | ~6%–24% Risk | Send STAT ADAMTS13; Clinical Judgment on Empiric TPE |
| PLASMIC 6–7 (High Risk, e.g., 6) | 62%–82% Risk | Immediate Therapeutic Plasma Exchange + Steroids ± Caplacizumab |
Bendapudi 7-Criterion PLASMIC Score (0 to 7, MAHA-Gated)
Requires confirmed microangiopathic hemolytic anemia with schistocytes (B2 = 1) first, then sums the 7 binary PLASMIC criteria B3:B9.
=IF(OR(MIN(B2:B9) < 0, MAX(B2:B9) > 1), "Flags Must Be 0 or 1", IF(B2 = 0, "Requires Schistocytic MAHA Prerequisite", SUM(B3:B9)))ISTH TTP Guideline Emergent Plasma Exchange Stratification
Classifies PLASMIC into Low (0–4), Intermediate (5), or High Probability of ADAMTS13 <= 10% (6–7).
=IF(OR(MIN(B2:B9) < 0, MAX(B2:B9) > 1), "Flags Must Be 0 or 1", IF(B2 = 0, "Requires Schistocytic MAHA Prerequisite", IF(SUM(B3:B9) >= 6, "High TTP Risk (PLASMIC 6–7 — Emergent Plasma Exchange + Steroids)", IF(SUM(B3:B9) = 5, "Intermediate TTP Risk (PLASMIC 5 — Send STAT ADAMTS13)", "Low TTP Risk (PLASMIC 0–4 — Evaluate Non-TTP TMA)"))))Try the example
Use the original values or change them to test your understanding.