A rapid test for the diagnosis of thrombotic thrombocytopenic purpura using surface enhanced laser desorption/ionization time-of-flight (SELDI-TOF)-mass spectrometry.
BACKGROUND
Thrombotic thrombocytopenic purpura (TTP), a life-threatening thrombotic microangiopathy, requires immediate diagnosis and plasma exchange therapy. Development of TTP is related to functional deficiency of ADAMTS-13 protease that leads to the accumulation of ultra large von Willebrand factor (VWF) and subsequent platelet thrombosis. Currently no clinical test is available for the rapid detection of ADAMTS-13 activity.


OBJECTIVE
The goal is to devise a novel method to rapidly detect functional activity of ADAMTS-13 and improve clinical outcome.


RESULTS
A recombinant VWF substrate containing the ADAMTS-13 cleavage site and a 6X Histidine tag was cleaved by ADAMTS-13 in a dose-dependent manner, generating approximately 7739 Da peptide containing a 6X Histidine tag. This cleaved peptide, bound to an IMAC/Nickel ProteinChip, was quantified using Surface Enhanced Laser Desorption/Ionization Time-of-flight Mass Spectrometry (SELDI-TOF-MS). The assay is capable of quantifying ADAMTS-13 activity as low as 2.5% in plasma within 4 h. When the cleaved peptide was quantified as a ratio of an internal control peptide, the test displayed good reproducibility, with an average inter-assay coefficient of variation (CV) of < 33%. Further validation revealed a mean ADAMTS-13 activity of 92.5% +/- 16.6% in 39 healthy donors. Sixteen patients with idiopathic TTP displayed mean ADAMTS-13 activity of 1.73% +/- 3.62%. Further utility of this novel method includes determining the inhibitory titer of ADAMTS-13 antibody in cases of acquired TTP.


CONCLUSIONS
We have devised a novel SELDI-TOF-MS assay that offers a rapid, cost-effective, and functionally relevant test for timely diagnosis and management of TTP.
Jin
M
M
Department of Pathology, Ohio State University College of Medicine and Public Health, Columbus, OH 43210, USA.
Cataland
S
S
Bissell
M
M
Wu
H M
HM
D051722:ADAM Proteins / Q000097:blood; D000071120:ADAMTS13 Protein; D016022:Case-Control Studies; D006801:Humans; D066298:In Vitro Techniques; D040081:Protein Array Analysis; D011697:Purpura, Thrombotic Thrombocytopenic / Q000097:blood* / Q000175:diagnosis*; D011993:Recombinant Fusion Proteins; D012016:Reference Values; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods* / Q000706:statistics & numerical data; D013379:Substrate Specificity; D014841:von Willebrand Factor / Q000032:analysis
D011993:Recombinant Fusion Proteins; D014841:von Willebrand Factor; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human