PB1323 - Assessing the Efficacy of the PLASMIC Score for Early Detection of Severe ADAMTS-13 Deficiency in Thrombotic Thrombocytopenic Purpura: A Single-Institution External Validation Study

Tuesday, June 25, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Presenting Author(s)

RS

Rishabh Singh

Resident
Department of Internal Medicine, University of Illinois College of Medicine Peoria, Peoria, IL, United States
Peoria, Illinois, United States

Co-Author(s)

SB

Simon Bechara

Resident
Department of Internal Medicine, University of Illinois College of Medicine Peoria, Peoria, IL, United States
Peoria, Illinois, United States
KS

Keerthana Sivakolundu

Resident
Department of Internal Medicine, University of Illinois College of Medicine Peoria, Peoria, IL, United States
Peoria, Illinois, United States
MT

Michael D. Tarantino

Professor
Department of Internal Medicine & Pediatrics, University of Illinois College of Medicine Peoria, Peoria, IL, United States
Peoria, Illinois, United States
JR

Jonathan Roberts

Associate Professor
Department of Internal Medicine & Pediatrics, University of Illinois College of Medicine Peoria, Peoria, IL, United States
Peoria, Illinois, United States
MK

Manasa Kandula

Associate Professor
Department of Internal Medicine, University of Illinois College of Medicine Peoria, Peoria, IL, United States
Peoria, Illinois, United States

Background: PLASMIC score was developed and validated (Li A. et al., 2018) to predict the likelihood of severe ADAMTS-13 deficiency in thrombotic microangiopathy (TMA).

Aims: Our study aimed to validate PLASMIC score’s accuracy in detecting Thrombotic Thrombocytopenic Purpura (TTP) and assess its role in reducing mortality through early plasma exchange therapy (PEX) in settings without in-house testing.

Methods: Our single-center retrospective cohort study assessed 374 inpatient ADAMTS-13 tests conducted from 2013 to 2023. Initial exclusions were patients < 16 years, repeat tests, and unavailable results, leaving 250 patients. We further excluded patients with absence of thrombocytopenia (13), MAHA (80), both (12), and previous PEX (4). 141 patients were eligible for PLASMIC score validation.

Results: We evaluated PLASMIC score's ability to predict severe ADAMTS-13 activity deficiency at high-risk scores of 6-7 (Table 1). At the ≤15% activity threshold, the score showed a sensitivity of 75% (57.68-92.32), specificity of 78.63% (71.21-86.06), a Positive Predictive Value (PPV) of 41.86% (27.12-56.61), and a Negative Predictive Value (NPV) of 93.88% (89.13-98.62). At ≤10% activity, sensitivity increased to 81.25% (62.13-100), while specificity slightly decreased to 76% (68.51-83.49). The PPV was 30.23% (16.51-43.96), and NPV was 96.94% (93.53-100). Further, PEX impact on survival was analyzed (Figure 1).
In a subgroup of 12 patients exhibiting ADAMTS-13 activity 10-30% and positive inhibitor, 6 patients who underwent PEX were alive after one year. Conversely, the other 6 patients who did not receive PEX did not survive, suggesting inhibitor presence may represent TTP in evolution.

Conclusion(s): The study emphasizes the PLASMIC score's utility in identifying high-risk patients for severe ADAMTS-13 deficiency. Initiating PEX promptly improved survival rates in both severe and low-intermediate risk groups, unlike the findings of Li A. et al., 2018, which indicated effectiveness only in high-risk patients. There may be clinical utility in repeat ADAMTS13 testing in declining TMA patients with positive inhibitors.