Digital Predictive Score
Predicts ADAMTS13 deficiency in suspected thrombotic thrombocytopenic purpura (TTP) with high discrimination
| PLASMIC Score | Risk group | |
| 0 to 4 | Low | |
| 5 | Intermediate | |
| 6 to 7 | High | |
|
• 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 *Severe deficiency was defined as ADAMTS13 activity level <15%. |
||
| 0 points | 1 points | |||
| Platelet count <30 x 109/L |
|
No
|
|
Yes
|
| Hemolysis* |
|
No
|
|
Yes
|
| Active cancer** |
|
Yes
|
|
No
|
| History of solid-organ or stem-cell transplant |
|
Yes
|
|
No
|
| MCV <9.0 x 10−14 L (<90 fL) |
|
No
|
|
Yes
|
| INR <1.5 |
|
No
|
|
Yes
|
| Creatinine <2.0 mg/dL (176.8 μmol/L) |
|
No
|
|
Yes
|
| Total score | Category |
| 0 | Low risk |
| Reset |
EVIDENCE APPRAISAL
The PLASMIC Score was derived by Bendapudi et al and externally validated in a study with an independent cohort of 112 consecutive hospitalized patients with suspected thrombotic microangiopathy and appropriate ADAMTS-13 testing (including 21 patients with TTP diagnosis). The PLASMIC model predicted severe ADAMTS-13 deficiency with a c statistic of 0.94 (0.88-0.98). When dichotomized at high (scores 6-7) vs. low-intermediate risk (scores 0-5), the model predicted severe ADAMTS-13 deficiency with positive predictive value 72%, negative predictive value 98%, sensitivity 90% and specificity 92%.
In the low-intermediate risk group (scores 0-5), there was no significant improvement in overall survival associated with plasma exchange. The PLASMIC Score had excellent applicability, discrimination and calibration for predicting severe ADAMTS-13 deficiency. The clinical algorithm allowed identification of a subgroup of patients who lacked a significant response to empiric treatment.
Reference
- 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.
- Li A, Khalighi PR, Wu Q, Garcia DA. External validation of the PLASMIC score: a clinical prediction tool for thrombotic thrombocytopenic purpura diagnosis and treatment. Thromb Haemost 2018;16(1):164-169
French Score
Each item is associated with one point (+1)
aResults correspond to those of the derivation cohort and those of a validation by (French score) the bootstrap resampling technique (internal validation)3,4 or (PLASMIC score) different samples of patients from the same institution (internal validation) or from a different institution (external validation).
bThe French score considered 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.
cMCV was not incorporated in the French score.
| French scoreb,c | |
| Platelet count |
<30 G/L
|
| Serum creatinine level |
<2.25 mg/dL
|
| Total score | Prediction of severe ADAMTS13 deficiency (activity <10%) based on scorea |
| 1 | 70% |
| Reset |
References
- Coppo P, et al. PLoS One. 2010;5(4):e10208
- Bendapudi PK, et al. Lancet Haematol. 2017;4(4):e157-e164
