McGlasson DL, Bessmer MS, Heatherly LA, Kaczor DA, Woodhams BJ, Sanchez JS, McKenzie SB. An evaluation using citrated whole blood to determine PT/INR, APTT, and fibrinogen assays on the STA automated coagulation analyzer. Clin Lab Sci 2001; 14:147.

We determined if citrated whole blood (WB) can be used to do coagulation assays on the STA, a Diagnostica Stago electromechanical, automated coagulation system. Thirty normal subjects, 60 coumadin patients and 10 heparinized patients were enrolled. Two Vacutainer citrated tubes were collected from each subject. One was used for WB testing, the other for platelet poor plasma (PPP). We applied a correction factor to compensate for the specimen differences. After correction, mean PT (PPP/WB) = 20.8/21.5 seconds (p = 0.01); INR = 2.44/2.26 (p = 0.75 NS); APTT = 44.3/42.5 (p = 0.33 NS); fibrinogen = 376/401 mg/dL (p = 0.03). Though differences for PT in seconds and fibrinogen rise to statistical significance at p < 0.05), these differences have no clinical consequence. Substituting WB for PTT may reduce turn-around and costs for routine coagulation assays.

Given the number of point of care instruments that perform PT/INR on whole blood, I wonder if the authors have extended this study in central laboratory operations.