PLASMIC Score for TTP
Predicts ADAMTS13 deficiency in suspected thrombotic thrombocytopenic purpura (TTP) with high discrimination.
Use in 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).
Result:
Why did you develop the PLASMIC Score for TTP? Was there a particular clinical experience or patient encounter that inspired you to create this tool for clinicians?
Within hematology, TTP represents a "sweet spot" for the development of a bedside diagnostic score: it is a lethal disease requiring immediate initiation of therapy but for which the gold standard diagnostic test takes 3-5 days to result. Given this situation, Robert Makar and I decided to leverage our institution's electronic medical record system to put together a curated cohort of TTP patients and try to identify common characteristics that could be used in a diagnostic score.
What pearls, pitfalls and/or tips do you have for users of the PLASMIC Score for TTP? Do you know of cases when it has been applied, interpreted, or used inappropriately?
The biggest mistake that clinicians make is trying to apply the score to the wrong population. The PLASMIC Score is intended for use only in patients with thrombocytopenia (platelets <150) and evidence of MAHA (schistocytes) on peripheral smear.
Other tips:
1. Use the earliest lab value available for each parameter. Do not use any value drawn after ≥72 hrs of hospitalization.
2. Combined hemolysis parameter: reticulocyte count >2.5 OR indirect bilirubin >2.0 OR haptoglobin undetectable. If any of these are positive, assign one point.
3. The PLASMIC Score is intended to support, not replace, clinical judgment.
What recommendations do you have for doctors once they have applied the PLASMIC Score for TTP? Are there any adjustments or updates you would make to the score based on new data or practice changes?
A patient's PLASMIC Score can be used to risk stratify that individual for further workup and treatment. We recommend a cutoff of 5, i.e. score <5 generally does not require further workup, score ≥5 usually requires ADAMTS13 to be sent along with expert consultation. For more information, please see Bendapudi et al 2017.
Any other research in the pipeline that you’re particularly excited about?
We continue to leverage our dataset to answer important clinical questions in the field of TTP and allied disorders, including other forms of thrombotic microangiopathy. We are also initiating a translational research program in which we are studying specimens from patients with TTP to better understand what predisposes people to TTP and how the disease may be prevented.
Pavan K. Bendapudi, MD, is an assistant professor of medicine at Harvard Medical School. Together with Dr. Robert Makar, he is co-principal investigator of the Harvard Thrombotic Microangiopathies Research Collaborative, an interdisciplinary, multi-institutional consortium that studies TTP and allied disorders. Dr. Bendapudi’s primary research is focused on humoral coagulation factors and the mechanisms underlying hemostatic and thrombotic disease.
- Alex Lazo, MD