Standardization of prothrombin times in newborn infants.

The prothrombin time (PT) for patients receiving warfarin varies widely, reflecting the heterogeneity of thromboplastin reagents. The International Committee on Thrombosis and Haemostasis recommends that PT values for these patients be expressed as international normalized ratios. This study showed that thromboplastin reagents also significantly influence PT values in neonatal plasma and that expressing PT values as international normalized ratios decreases this variability.