Statistical & Clinical Analysis
French TMA Score (Coppo Rule): Severe ADAMTS13 Deficiency Probability in TTP (0 to 3)
Differentiate immune Thrombotic Thrombocytopenic Purpura (iTTP, ADAMTS13 < 10%) from atypical HUS in thrombotic microangiopathy using Paul Coppo’s ISTH-endorsed French TMA Score (Platelets <= 30 × 10⁹/L + Creatinine <= 200 umol/L + ANA positive).
Why profound thrombocytopenia WITH preserved renal function points strongly toward ADAMTS13-deficient iTTP!
Paul Coppo, Antoine Froissart, and the French Reference Center for Thrombotic Microangiopathies (2010, PLoS ONE — ISTH TTP guidelines alongside PLASMIC) showed that once cancer-, transplant-, and Shiga-toxin-associated TMAs are excluded, immune TTP (severe ADAMTS13 activity < 10%) exhibits much lower platelet counts and much MILDER acute kidney injury than complement-mediated atypical HUS (aHUS)!
In adults presenting with microangiopathic hemolytic anemia (schistocytes + elevated LDH), the French TMA Score assigns +1 point each for: Platelet count <= 30 × 10^9/L, Serum Creatinine <= 200 umol/L (<= 2.26 mg/dL), and Positive Antinuclear Antibodies (ANA) (or 2-variable bedside version 0–2 when urgent ANA is pending: Platelets <= 30 + Creatinine <= 200 -> 2/2 carries > 93% PPV for severe ADAMTS13 deficiency, justifying immediate therapeutic plasma exchange and caplacizumab/corticosteroids while awaiting ADAMTS13 assay)!
| French TMA Score (0–3 Points) | Severe ADAMTS13 (< 10%) Probability | ISTH Emergent TMA Management |
|---|---|---|
| Score 2–3 (e.g., Plt 14, Cr 118, ANA+) | ~85%–98% Severe ADAMTS13 Deficiency | Immediate Plasma Exchange + Immunosuppression ± Caplacizumab |
| Score 1 (Mixed TMA Phenotype) | Intermediate Probability (~40%–55%) | Empiric PEX Judgment + Urgent STAT ADAMTS13 Assay |
| Score 0 (e.g., Plt 68, Cr 410 umol/L) | < 5% iTTP (Favors Complement aHUS) | Evaluate Complement Blockade (Eculizumab/Ravulizumab) Workup |
Coppo French TMA Score (0 to 3 Points from Raw Platelets, Creatinine umol/L & ANA)
Evaluates (Platelets <= 30) + (Creatinine <= 200 umol/L) + ANA_Positive directly from raw lab values.
=IF(OR(B2 <= 0, B3 <= 0, B4 < 0, B4 > 1), "Invalid TMA Lab Inputs", IF(B2 <= 30, 1, 0) + IF(B3 <= 200, 1, 0) + B4)ISTH French TMA Emergent Plasma Exchange Stratification
Classifies French TMA Score >= 2 as High Probability iTTP, 1 as Intermediate, and 0 as Low Probability (aHUS phenotype).
=IF(OR(B2 <= 0, B3 <= 0, B4 < 0, B4 > 1), "Invalid TMA Lab Inputs", IF(IF(B2 <= 30, 1, 0) + IF(B3 <= 200, 1, 0) + B4 >= 2, "High iTTP Probability (French Score >= 2 — Emergent PEX / Caplacizumab Pathway)", IF(IF(B2 <= 30, 1, 0) + IF(B3 <= 200, 1, 0) + B4 = 1, "Intermediate iTTP Probability (French Score = 1 — STAT ADAMTS13)", "Low iTTP Probability (French Score = 0 — Evaluate aHUS / Secondary TMA)")))Try the example
Use the original values or change them to test your understanding.