PB0075 - Evaluation of ADAMTS13 activity (A13) cut-off: A13-AcuDiag retrospective study.

Sunday, June 23, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Co-Author(s)

EJ

EMILIE JOUSSELME

Medical Biologist
University Hospital of Lyon
BRON, Rhone-Alpes, France

Co-Author(s)

CD

CLEMENT D'AUDIGIER

Medical Biologist
University Hospital of Besançon
BESANCON, Franche-Comte, France
MD

MAGALI DONNARD

Medical Biologist
University Hospital of Limoges
LIMOGES, Limousin, France
IH

INES HARZALLAH

Medical Biologist
Groupe Hospitalier de la région Mulhouse Sud Alsace
MULHOUSE, Alsace, France
NH

NATHALIE HEZARD

Medical Biologist
University Hospital of Timone
MARSEILLE, Provence-Alpes-Cote d'Azur, France
CL

COLINE LEGENDRE

Medical Biologist
University Hospital of Saint-Etienne
SAINTE ETIENNE, Rhone-Alpes, France
JP

JEREMY PEROTTET

Medical Biologist
University Hospital of Caen Normandie
CAEN, Basse-Normandie, France
MT

MARIE TOUSSAINT-HACQUARD

Medical Biologist
University Hospital of Nancy
NANCY, Lorraine, France

Presenting Author(s)

CHRISTOPHE NOUGIER

Medical Biologist
University Hospital of Lyon
BRON, Rhone-Alpes, France

Background: Severe A13 deficiency characterizes Thrombotic Thrombocytopenic Purpura (TTP). Even if A13 < 10% is published as specific for TTP, this cut-off is not based on the assay used. This threshold is also applied through the HemosIL AcuStar A13 assay, a rapid, fully-automated and reliable method developed with a low limit of detection.

Aims: Determine if the 10% cut-off is discriminant for the automated method.

Methods: We collected A13 results, antibody presence, clinical scores and final diagnosis of patients who were suspected of TTP for the first time. Each of the French participating laboratories sent the data of all relevant cases since the installation of the assay.

Results: We collected data for 69 patients from 8 laboratories between May 2021 and August 2023 (Figures 1, 2).
- 46 patients (67%) had immune TTP (iTTP). Among them, 33 plasmas had undetectable activities and 13 had activities between 0.2 to 3.1%. French scores were ≥ 2 (96%).
- 2 patients had non-immune TTP (niTTP) and 1 patient a mixed form (TTP/ Hemolytic Uremic Syndrome). A13 in this group were greater than 0.2 but below 10%. No antibody have been reported. Scores were not elevated or not evaluable (sepsis).
- 20 patients (29%) had no TTP. Among them, only 3 had A13 between 5 -10%, with no antibody. The score was low or not evaluable for 2 patients (sepsis, pregnancy).
For iTTP, 100% of A13 were < 5%, 72% < 0.2%. For no-TTP, 100% of A13 were >5%.

Conclusion(s): On the ACL AcuStar, A13 between 5 and 10% should be discussed. A13 < 0.2%, without additional signs related to another clinical condition preexisting or without congenital deficiency suspicion, seems to be highly predictable of iTTP and may help clinician to start more quickly immune treatment. These observations should be validated in a prospective study in process.