Reliability of delayed prothrombin time INR determinations in a central laboratory using off-site blood sampling.
A major concern of centralized anticoagulant measurements with off-site sampling is the reliability of international normalized ratio (INR) determinations on blood that may have been taken from the patient hours before the analysis. We compared INR differences in the blood of patients receiving oral anticoagulants after 24 h storage in four conditions: centrifuged at room temperature, centrifuged at 4 degrees C, uncentrifuged at room temperature and uncentrifuged at 4 degrees C. The INR of centrifuged and uncentrifuged blood left at room temperature for 24 h consistently increased by 6% and, after adjustment, there were no misclassifications in the assessment of the adequacy of anticoagulant treatment. Inconsistent changes were noted in tests of refrigerated centrifuged blood. We conclude that storage of blood at room temperature for 24 h results in a consistent prolongation of the prothrombin time, which after correction can reliably be used to adjust the dose of oral anticoagulants.
Froom
P
P
Central Laboratory of Haifa and Western Galilee, Clalit Health Services, Nesher, Israel.
Abramova
D
D
Bar-El
M
M
Barak
M
M
D000925:Anticoagulants / Q000627:therapeutic use; D001793:Blood Preservation; D001800:Blood Specimen Collection / Q000379:methods* / Q000592:standards; D002498:Centrifugation; D003951:Diagnostic Errors; D016903:Drug Monitoring / Q000592:standards; D006801:Humans; D019934:International Normalized Ratio / Q000592:standards*; D011517:Prothrombin Time; D015203:Reproducibility of Results; D013696:Temperature
D000925:Anticoagulants