PLASMIC Score for TTP

PLASMIC Score Calculator

Platelet Count <30,000/µL

Hemolysis (reticulocyte >2.5%, haptoglobin undetectable, or indirect bilirubin >2 mg/dL)

No Active Cancer

No Solid Organ or Stem Cell Transplant

MCV <90 fL

INR <1.5

Creatinine <2.0 mg/dL

PLASMIC Score: 0

Low Risk

Score 0: Low risk (<2% likelihood of ADAMTS13 severely deficient). Consider alternative diagnoses.

Predicts ADAMTS13 deficiency in suspected thrombotic thrombocytopenic purpura (TTP) with high discrimination.

Why Use

Helps distinguish TTP from other causes of thrombotic microangiopathy. ADAMTS-13 confirmatory testing takes several days, so a clinical score can help clarify the clinical picture and aid in decisions to initiate treatment. Starting plasma exchange early in intermediate and high risk patients improves survival (mortality for untreated TTP is >90%).

When to Use

Hospitalized adult inpatients with suspected thrombotic thrombocytopenic purpura (TTP) who might benefit from early initiation of plasma exchange while awaiting ADAMTS-13 results. Do not use in patients who have already undergone plasma exchange (i.e., intermediate and high risk groups, in whom therapeutic plasma exchange must be initiated immediately).

Formula

Addition of the selected points: Variable 0 points 1 point P latelet count <30 x 10 9 /L No Yes Hemo l ysis* No Yes A ctive cancer** Yes No History of solid-organ or s tem-cell transplant Yes No M CV <9.0 x 10 -14 L (<90 fL) No Yes I NR <1.5 No Yes C reatinine <2.0 mg/dL (176.8 μmol/L) No Yes *Reticulocyte count >2.5%, haptoglobin undetectable, or indirect bilirubin >2.0 mg/dL (34.2 µmol/L). **Treated for cancer within the past year. From Bendapudi 2017 .

Pearls / Pitfalls

TTP can have very nonspecific symptoms, so clinical suspicion must be high. Generally, very low platelets and hemolytic anemia are TTP until proven otherwise. Has high sensitivity to rule out TTP and may help distinguish TTP from a broad range of thrombotic microangiopathies. Not validated for pediatric patients. Samples for ADAMTS-13 level and ADAMTS-13 inhibitor must be drawn before initiation of any therapy (results may take a few days or longer, depending on the laboratory workflow).

Management

Most hospitals will require patients on plasma exchange to be transferred to a critical care unit for closer observation. Therapeutic plasma exchange remains the first-line treatment. Plasma transfusion is indicated if plasma exchange cannot be performed immediately. Red blood cell transfusion can be given to patients with severe bleeding. Glucocorticosteroids are often given as adjunctive treatment. Management is ideally carried out in consultation with hematology-oncology and transfusion medicine services.

Advice

Low risk (PLASMIC Scores ≤4): consider alternative diagnoses. Intermediate risk (PLASMIC Score 5): send ADAMTS-13 testing, keep close observation, obtain expert consultation, consider plasma exchange if no other cause identified. High risk (PLASMIC Scores ≥6): send for ADAMTS-13 testing, obtain expert consultation, immediate plasma exchange.

More Information

Interpretation: PLASMIC Score Risk group Risk of severe ADAMTS13 deficiency* 0-4 Low 0% 5 Intermediate 6% 6-7 High 72% *Severe deficiency was defined as ADAMTS13 activity level <15%. From Li 2018 .