ADAMTS13 Associated With Immune Thrombotic Thrombocytopenic Purpura

Researchers investigated patients with immune thrombotic thrombocytopenic purpura (iTTP) to identify predictive factors for burden of care and need of immunosuppressive treatment with early rituximab rescue therapy. After analysis, the authors reported that ADAMTS13 inhibitor titer level at time of diagnosis was an effective biomarker for iTTP. Their findings were published in Clinical and Applied Thrombosis/Hemostasis.

This study enrolled 42 retrospective patients with iTTP from 3 centers with individual-level data collected in the 24 hours following initial presentation. The researchers used enzyme-linked immunosorbent assays to evaluate ADAMTS13 activity and inhibitors. Additionally, researchers compared total plasma exchange sessions, number of sessions needed to achieve a clinical response, and duration of hospitalization.

ADAMTS13 Inhibitor Levels Linked to Slower Response to Treatment

According to the authors, the median ADAMTS13 activity percentage value was 0.02 IU (interquartile range [IQR], 0.01-0.02) and mean ADAMTS13 inhibitor titer was 66.37 ± 34.59 BU/ml. Patients had a median of 0.04 days (IQR, 0.02-0.06) from admission to platelet exchange initiation.

The median number of sessions to achieve clinical response was 7.00 (IQR, 4.00-14.75; n=38), and the median total number of sessions was 14.00 (IQR, 8.00-19.00; n=41). Based on 41 patients with available data, the median duration of hospitalization was 20.00 days (IQR, 12.00-27.00) and median days in the intensive care unit was 1.00 (IQR, 0.00-11.00). After a median follow-up of 26 months, 9 patients (21.40%) had at least 1 relapse.

The authors noted 6 patients had an exacerbation during the first 30 days of treatment. This subgroup of patients had the following characteristics:

  • Median ADAMTS13 activity: 0.02 IU
  • Median ADAMTS13 inhibitor: 49.45 BU
  • Median total number of platelet exchange sessions: 18
  • Median number of sessions until clinical response: 13
  • Median duration of hospitalization: 21 days

A significant correlation was found between ADAMTS13 inhibitor titer at diagnosis with total number of platelet exchange sessions (Pearson correlation coefficient [r]=0.46) and number of sessions needed to achieve clinical response (r=0.48). Additionally, the researchers identified a significant difference in median ADAMTS13 inhibitor titer at diagnosis between patients who required rituximab rescue therapy and patients who responded to steroids alone.

In short, the study’s authors suggested that ADAMTS13 inhibitor titer “could be a useful tool for management of new iTTP cases and an interesting variable to optimize iTTP case stratification in future caplacizumab cost-efficacy analysis.”

Related: Value of Peripheral Blood Lymphocytes in Detecting Immune Thrombocytopenia