From Bob Gosselin: Hey GF, re point of care (POC) international normalized ratios (INRs), assuming that you are collecting a citrated sample for testing, a high hematocrit (HCT) should not matter for a system that employs fingerstick whole blood, since there is no citrate:plasma ratio issue at hand with using whole blood. Viscosity may be an issue with high HCTs and POC testing.
Robert Gosselin, CLS
Coagulation Specialist, University of California, Davis Health System
Department of Pathology and Laboratory Medicine, Specialty Testing Center
Thanks Bob, this is a helpful comment. I took the 25–55% comment from the cartridge package inserts for the Coag-U-Chek and the iSTAT instruments, but I suspect they set limits based either on current plasma-based standards or perhaps just because they never tested their cartridges outside these limits. I agree, it would seem as though HCT should not affect the PT/INR from a capillary puncture. Geo.