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Validation of PLASMIC score: an academic medical center case series (2012-present)
Harrison Moosavi1, Yamin Ma1, Maureen J Miller1
1Department of Pathology and Laboratory Medicine, Center for Transfusion and Cellular Therapies, Emory University School of Medicine, Atlanta, Georgia, USA.
Background:
The PLASMIC score is a rapid and inexpensive tool for predicting severe ADAMTS13 deficiency (activity <10%) in patients with suspected thrombotic thrombocytopenic purpura (TTP) by analyzing seven parameters (platelet count; combined hemolysis variable; absence of active neoplasia; absence of an organ or stem-cell transplant; mean corpuscular value; international normalized ratio; and serum creatinine). The purpose of this study was to validate the PLASMIC score at a large multi-institutional academic medical center.
Methods:
An internal database of consultations to the transfusion medicine service, which oversees therapeutic apheresis at our institution, was reviewed to identify patients who were evaluated for and/or received plasma exchange for suspected TTP. These consultations covered the time period of January 2012 to February 2019. PLASMIC scoring criteria and ADAMTS13 assay results were abstracted from the electronic medical record, the PLASMIC score was calculated, and cases stratified into risk categories (low, intermediate, high risk) based on the score value.
Results:
Of 58 patients identified, 46 met inclusion criteria, and 27 demonstrated ADAMTS13 activity <10%. Correlation of severe ADAMTS13 deficiency with risk-stratified groups resulted in 78% sensitivity, 63% specificity, 75% positive predictive value (PPV), and 67% negative predictive value (NPV).
Discussion:
These findings paralleled those from validation studies performed at other institutions. They provided insufficient evidence to recommend routine use of the PLASMIC score to rule out TTP among patients at our hospitals. Nonetheless, these results reinforce the importance of early ADAMTS13 testing as a diagnostic triage tool for patients with suspected TTP.
