Comparison of the aPTT with alternative tests for monitoring direct thrombin inhibitors in patient samples.
OBJECTIVE
The activated partial thromboplastin time (aPTT) test has been used for years to monitor parenteral direct thrombin inhibitors (DTIs) and unfractionated heparin. Because the aPTT correlates poorly with unfractionated heparin levels, we hypothesized that the aPTT may not be the best test for monitoring parenteral DTIs.


METHODS
Using 235 excess plasma specimens from 82 adult patients receiving treatment with DTIs (argatroban, bivalirudin, or dabigatran), we compared the aPTT with the ecarin chromogenic assay (ECA), the dilute thrombin time (dTT) test, and the prothrombinase-induced clotting time (PiCT) test.


RESULTS
The aPTT correlated poorly with each of the other tests in both bivalirudin- and argatroban-containing samples (r(2) = 0.04-0.23). The ECA and dTT exhibited the best correlations (r(2) = 0.66-0.93). Intermediate correlations were seen when the results of the PiCT were plotted against the dTT or ECA (r(2) = 0.46-0.58). Nineteen specimens obtained from six patients receiving dabigatran showed a good correlation between the dTT and the ECA (r(2) = 0.92).


CONCLUSIONS
The aPTT does not correlate well with other tests that might be used to monitor parental DTI administration. Further studies are needed to evaluate the clinical usefulness of alternative tests and their correlation with clinical outcomes.
University of Colorado Hospital, Box A022, 1665 Aurora Ct, Aurora, CO 80111; stuart. lind@ucdenver.edu.
Stuart E
SE
Lind
Mary Ellen
ME
Boyle
Sheila
S
Fisher
Jan
J
Ishimoto
Toby C
TC
Trujillo
Tyree H
TH
Kiser
D000991:Antithrombins / Q000494:pharmacology*; D001120:Arginine / Q000031:analogs & derivatives; D001562:Benzimidazoles / Q000494:pharmacology; D001777:Blood Coagulation / Q000187:drug effects / Q000502:physiology; D001780:Blood Coagulation Tests / Q000379:methods; D000069604:Dabigatran; D016903:Drug Monitoring / Q000379:methods; D006493:Heparin / Q000494:pharmacology; D006629:Hirudins / Q000494:pharmacology; D006801:Humans; D010314:Partial Thromboplastin Time / Q000379:methods; D010446:Peptide Fragments / Q000494:pharmacology; D010875:Pipecolic Acids / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D013449:Sulfonamides; D013917:Thrombin / Q000037:antagonists & inhibitors*; D013918:Thrombin Time; D013925:Thromboplastin / Q000494:pharmacology; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000494:pharmacology
D000991:Antithrombins; D001562:Benzimidazoles; D006629:Hirudins; D010446:Peptide Fragments; D010875:Pipecolic Acids; D011994:Recombinant Proteins; D013449:Sulfonamides; D015091:beta-Alanine; D006493:Heparin; D013925:Thromboplastin; D001120:Arginine; D013917:Thrombin; D000069604:Dabigatran; C031942:argatroban; C074619:bivalirudin
Argatroban; Bivalirudin; Dabigatran; Ecarin; Monitoring; Thrombin time; aPTT