Tools to support a clinical aTTP diagnosis


PLASMIC and French scores can be used to predict ADAMTS13 deficiency1

PLASMIC and French scores are based on laboratory parameters such as platelet count and creatinine level.2

    Plasmic Score1

    Parameter

     

    Score

    Platelet count <30 × 109/L

     

    +1

    Serum creatinine level <2.0 mg/dL

     

    +1

    Evidence of hemolysis*:
       Indirect bilirubin >2.0 mg/dL
       or Reticulocyte count >2.5%
       or Undetectable haptoglobin

     

    +1

    No active cancer in previous year*

     

    +1

    No history of solid organ or stem cell transplantation*

     

    +1

    INR <1.5*

     

    +1

    MCV <90 fL (<9.0 × 10-14/L)†

     

    +1

     

    Likelihood of severe
    ADAMTS13 deficiency‡

    Low risk

    0 to 4: 0% to 4%

    Intermediate risk

    5: 5% to 24%

    High risk

    6 to 7: 62% to 82%

    Likelihood of severe
    ADAMTS13 deficiency‡

    Low risk

     

     

     

    0 to 4: 0% to 4%
    Intermediate risk

     

    5: 5% to 24%
    High risk

     

    6 to 7: 62% to 82%

    Validation of the PLASMIC score1

     

    Derivation validation cohort
    (n=200)

    Internal validation cohort
    (n=150)

    External validation cohort
    (n=146)

    0-4

    0/84 (0%)

    0/89 (0%)

    2/47 (4%)

    5

    2/44 (5%)

    3/32 (9%)

    6/25 (24%)

    6-7

    58/72 (81%)

    18/29 (62%)

    61/74 (82%)

    These data refer to the number of individuals with ADAMTS13 activity ≤10% and to the total number of individuals with this score.3

    The PLASMIC score can predict severe ADAMTS13 activity as criteria for identifying a patient with probable TTP, such as3:

    •Absence of clinical conditions that can justify microangiopathy (eg, cancer, transplant, DIC)
    •Presence of severe thrombocytopenia (<30 × 109/L)
    •Mild or no renal insufficiency (creatinine)
     

    This score does not replace a TTP diagnosis, which is based on the activity of ADAMTS13 and anti-ADAMTS13 antibodies.2

    French Score1

    Parameter

    Score

    Platelet count <30 × 109/L

    +1

    Serum creatinine level <2.25 mg/dL

    +1

     

     

    Prediction of severe ADAMTS13 deficiency
    (activity <10%) based on score‡

    0: 2%

     

    1: 70%

     

    2: 94%

     

The PLASMIC and French scores can be a valid help in cases of diagnostic suspicion to quickly identify if a patient needs emergency treatment2

The ISTH TTP Guidelines can help inform diagnosis and your treatment approach.

See the Guidelines

Quickly differentiating TMAs can help prevent devastating consequences.

See the types of TMAs

ADAMTS13=a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13; DIC=disseminated intravascular coagulation; INR=international normalized ratio; MCV=mean corpuscular value.

Each item is associated with one point (+1).
*The French score considers patients with a thrombotic microangiopathy syndrome (which includes hemolysis with schistocytes in the definition) and assumes that there is no history of or clinical evidence for associated cancer, transplantation, or disseminated intravascular coagulopathy, so these items are intrinsic to the score.1
†MCV was not incorporated into the French score.1
‡Results correspond to those of the derivation cohort and those of a validation by (French score) the bootstrap resampling technique (internal validation) or (PLASMIC score) different samples of patients from the same institution (internal validation) or from a different institution (external validation).1

References: 1. Coppo P, Cuker A, George JN. Thrombotic thrombocytopenic purpura: toward targeted therapy and precision medicine. Res Pract Thromb Haemost. 2019;3(1):26-37. doi:10.1002/rth2.12160 2. Zheng XL, Vesely SK, Cataland SR, et al. ISTH guidelines for the diagnosis of thrombotic thrombocytopenic purpura. J Thromb Haemost. 2020;18(10):2486-2495. doi:10.1111/jth.15006 3. Bendapudi PK, Hurwitz S, Fry A, et al. Derivation and external validation of the PLASMIC score for rapid assessment of adults with thrombotic microangiopathies: a cohort study. Lancet Haematol. 2017;4(4):e157-e164. doi:10.1016/S2352-3026(17)30026-1