Second international collaborative study evaluating performance characteristics of methods measuring the von Willebrand factor cleaving protease (ADAMTS-13).
BACKGROUND
Over the last 4 years ADAMTS-13 measurement underwent dramatic progress with newer and simpler methods.


OBJECTIVE
Blind evaluation of newer methods for their performance characteristics.


METHODS
The literature was searched for new methods and the authors invited to join the evaluation. Participants were provided with a set of 60 coded frozen plasmas that were prepared centrally by dilutions of one ADAMTS-13-deficient plasma (arbitrarily set at 0%) into one normal-pooled plasma (set at 100%). There were six different test plasmas ranging from 100% to 0%. Each plasma was tested 'blind' 10 times by each method and results expressed as percentage vs. the local and the common standard provided by the organizer.


RESULTS
There were eight functional and three antigen assays. Linearity of observed-vs.-expected ADAMTS-13 levels assessed as r2 ranged from 0.931 to 0.998. Between-run reproducibility expressed as the (mean) CV for repeated measurements was below 10% for three methods, 10-15% for five methods and up to 20% for the remaining three. F-values (analysis of variance) calculated to assess the capacity to distinguish between ADAMTS-13 levels (the higher the F-value, the better the capacity) ranged from 3965 to 137. Between-method variability (CV) amounted to 24.8% when calculated vs. the local and to 20.5% when calculated vs. the common standard. Comparative analysis showed that functional assays employing modified von Willebrand factor peptides as substrate for ADAMTS-13 offer the best performance characteristics.


CONCLUSIONS
New assays for ADAMTS-13 have the potential to make the investigation/management of patients with thrombotic microangiopathies much easier than in the past.
Tripodi
A
A
Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Department of Internal Medicine and Medical Specialties, University and IRCCS Maggiore Hospital, Milan, Italy. armando.tripodi@unimi.it
Peyvandi
F
F
Chantarangkul
V
V
Palla
R
R
Afrasiabi
A
A
Canciani
M T
MT
Chung
D W
DW
Ferrari
S
S
Fujimura
Y
Y
Karimi
M
M
Kokame
K
K
Kremer Hovinga
J A
JA
Lämmle
B
B
de Meyer
S F
SF
Plaimauer
B
B
Vanhoorelbeke
K
K
Varadi
K
K
Mannucci
P M
PM
D051722:ADAM Proteins / Q000097:blood*; D000071120:ADAMTS13 Protein; D003299:Cooperative Behavior; D006801:Humans; D006868:Hydrolysis; D012015:Reference Standards; D015203:Reproducibility of Results; D014841:von Willebrand Factor / Q000378:metabolism*
D014841:von Willebrand Factor; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human