European concerted action on anticoagulation. Use of plasma samples to derive international sensitivity index for whole-blood prothrombin time monitors.
BACKGROUND
To simplify International Sensitivity Index (ISI) calibration, the possibility of substituting fresh plasma for fresh whole-blood samples with point-of-care testing (POCT) whole-blood monitors was investigated in a three-center study of three different POCT systems.


METHODS
A modified full WHO calibration procedure based on 20 healthy controls and 60 coumarin-treated patients was performed on three monitoring systems with whole-blood and plasma samples against plasma tested using the European Concerted Action on Anticoagulation (ECAA) rabbit reference plain thromboplastin and the manual prothrombin time (PT) method.


RESULTS
With one of the three systems, the mean ISI was 1.51 for whole blood and 1.49 for plasma; with the second system, the mean ISI was 1.08 for both whole blood and plasma. With the third system, however, the difference between the mean ISI for whole blood and that for plasma was greater (1.15 and 1.01, respectively). Overall, the precision of the calibrations was less than with traditional manual plasma PT testing.


CONCLUSIONS
Provided that an appropriate calcium chloride concentration is used, the plasma PT results can be used for accurate ISI calibration of two of these three whole-blood POCT systems. Precision criteria need to be modified for POCT monitors.
Poller
Leon
L
European Concerted Action on Anticoagulation (ECAA) Central Facility, School of Biological Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom. ecaa@man.ac.uk
Keown
Michelle
M
Chauhan
Nikhil
N
van den Besselaar
Anton M H P
AM
Meeuwisse-Braun
Joyce
J
Tripodi
Armando
A
Clerici
Mariagrazia
M
Jespersen
Jørgen
J
D000284:Administration, Oral; D000818:Animals; D000925:Anticoagulants / Q000627:therapeutic use*; D002138:Calibration; D003374:Coumarins / Q000627:therapeutic use; D005060:Europe; D006801:Humans; D007391:International Cooperation; D019934:International Normalized Ratio; D010949:Plasma; D019095:Point-of-Care Systems; D011517:Prothrombin Time; D011817:Rabbits; D012015:Reference Standards; D012016:Reference Values; D013925:Thromboplastin / Q000592:standards
D000925:Anticoagulants; D003374:Coumarins; D013925:Thromboplastin; C030123:coumarin