A statistical and clinical evaluation of fingerstick and routine laboratory prothrombin time measurements.
OBJECTIVE
To compare prothrombin time measurements by fingerstick and routine laboratory methods.


METHODS
Prospective cohort study.


METHODS
University-affiliated anticoagulation clinic.


METHODS
Thirty-three patients receiving warfarin with stable anticoagulation for 3 months preceding the two studies.


METHODS
Groups 1 (17 patients) and 2 (16 patients) provided 150 and 125 paired samples, respectively, for fingerstick and routine laboratory analysis. The fact that no patient required a dosage change allowed for a clinical assessment.


RESULTS
Correlation and agreement between methods were good in group 1 but poor in group 2. Fingerstick results were less variable (smaller standard deviation and smaller coefficient of repeatability) in both groups. By analysis of discrepant pairs (25 in group 1, 63 in group 2), the routine laboratory results indicated dosage changes erroneously more often than did the fingerstick method.


CONCLUSIONS
In these two trials, the fingerstick system was superior to the routine laboratory method in that it was more reliable (less variability and more repeatable) and less likely to indicate dosage changes erroneously.
Bussey
H I
HI
Division of Pharmacotherapy, University of Texas Health Science Center at San Antonio, 78284-6220, USA.
Chiquette
E
E
Bianco
T M
TM
Lowder-Bender
K
K
Kraynak
M A
MA
Linn
W D
WD
Farnett
L
L
Clark
G M
GM
D000925:Anticoagulants / Q000008:administration & dosage / Q000627:therapeutic use; D001780:Blood Coagulation Tests / Q000379:methods* / Q000706:statistics & numerical data; D015331:Cohort Studies; D003657:Decision Making; D003955:Diagnostic Tests, Routine / Q000379:methods* / Q000706:statistics & numerical data; D005069:Evaluation Studies as Topic; D006801:Humans; D011446:Prospective Studies; D011517:Prothrombin Time; D012044:Regression Analysis; D015203:Reproducibility of Results
D000925:Anticoagulants