The PLASMIC score was developed in 2017 by the Harvard Thrombotic Microangiopathies (TMA) Research Collaborative to assist in the diagnosis and management of thrombotic thrombocytopenic purpura (TTP). When applied to the appropriate patient population, the score accurately distinguishes between TMA patients with and without severe ADAMTS13 deficiency (defined as ADAMTS13 activity level ≤10%). This tool is intended for use as an adjunct in the diagnosis of TTP, not as a replacement for appropriate clinical judgement.

The name “PLASMIC” refers to the score’s seven components: Platelet count; combined hemoLysis variable; absence of Active cancer; absence of Stem-cell or solid-organ transplant; MCV; INR; Creatinine.

Application of the PLASMIC score should be restricted to patients with a platelet count <150,000 per microliter and schistocytes visible on the peripheral blood smear.

For new presentations: use earliest available laboratory value for each parameter. For inpatients: use laboratory values obtained on the day of inpatient admission when TTP was first suspected.

0 points

Founded in 2012, the Harvard TMA Research Collaborative is a multi-institutional, inter-disciplinary project bringing together several large academic medical centers in Boston, Massachusetts with the goal of studying TTP and allied disorders. Our registry contains well-curated, patient-level data for individuals with TTP associated with severe ADAMTS13 deficiency and other forms of thrombotic microangiopathy. As a result, we have reported one of the nation’s largest experiences in this disorder and are engaged in several ongoing studies related to its diagnosis and management.

Participating centers include the three main teaching hospitals of Harvard Medical School: Beth Israel Deaconess Medical Center, Brigham and Women’s Hospital, and Massachusetts General Hospital. The Collaborative is based at Massachusetts General Hospital and is led by Dr. Pavan K. Bendapudi (Division of Hematology and Blood Transfusion Service) and Dr. Robert S. Makar (Blood Transfusion Service).

The PLASMIC score was derived using 29 clinical and laboratory parameters collected from 62 patients with TMA associated with severe ADAMTS13 deficiency and 179 control patients with other forms of TMA. Severe ADAMTS13 deficiency was defined as an ADAMTS13 activity level of ≤10%. Parameters were screened by univariate analysis to identify those most predictive of severe ADAMTS13 deficiency, and these variables were then subjected to multivariate regression modeling. The final seven components of the score were chosen based on a combination of modeling results and expert opinion. Components of the score were weighted based on their beta coefficients. The goal was to generate a parsimonious clinical prediction tool that maximizes both accuracy and ease of use.

Following derivation, the PLASMIC score underwent two rounds of validation. An internal validation was performed on a dataset collected prospectively within the Harvard system (N=150), resulting in a C statistic of 0.95. A second, external validation was performed against a dataset of patients from the University of Alabama (N=146), resulting in a C statistic of 0.91. Following validation, the performance of the PLASMIC score was compared against the use of clinical judgement alone. As measured by the C statistic, Brier Score, and Integrated Discrimination Improvement (IDI), the PLASMIC score outperformed the clinical consensus diagnosis of a panel of three physicians.

Citation:

Pavan K. Bendapudi, Shelley Hurwitz, Ashley Fry, Marisa B. Marques, Stephen W. Waldo, Ang Li, Lova Sun, Vivek Upadhyay, Ayad Hamdan, Andrew M. Brunner, John M. Gansner, Srinivas Viswanathan, Richard M. Kaufman, Lynne Uhl, Christopher P. Stowell, Walter H. Dzik, and Robert S. Makar. “Derivation and External Validation of the PLASMIC Score for the Rapid Assessment of Adults with Thrombotic Microangiopathies: a Cohort Study.” Lancet Haematology (4):e157-e164. doi: 10.1016/S2352-3026(17)30026-1 (2017).

The Harvard TMA Research Collaborative Dataset:

Bendapudi PK, Li A, Hamdan A, Uhl L, Kaufman R, Stowell C, Dzik W, Makar RS. “Impact of severe ADAMTS13 deficiency on clinical presentation and outcomes in patients with thrombotic microangiopathies: the experience of the Harvard TMA Research Collaborative.” Br J Haematology 171(5): 836-844 (2015).

The PLASMIC Score:

Pavan K. Bendapudi, Shelley Hurwitz, Ashley Fry, Marisa B. Marques, Stephen W. Waldo, Ang Li, Lova Sun, Vivek Upadhyay, Ayad Hamdan, Andrew M. Brunner, John M. Gansner, Srinivas Viswanathan, Richard M. Kaufman, Lynne Uhl, Christopher P. Stowell, Walter H. Dzik, and Robert S. Makar. “Derivation and External Validation of the PLASMIC Score for the Rapid Assessment of Adults with Thrombotic Microangiopathies: a Cohort Study.” Lancet Haematology (4):e157-e164. doi: 10.1016/S2352-3026(17)30026-1 (2017).

PLASMIC Score-Based Treatment Recommendations for Suspected TTP:

Bendapudi, P.K., Upadhyay, V., Sun, L., Marques, M.B., and Makar, R.S. “Clinical Scoring Systems in Thrombotic Microangiopathies.” Seminars in Thrombosis and Haemostasis 43(5): 540-548. doi: 10.1055/s-0037-1603100 (2017).