Statistical comparison of the fibrometer and the Electra 600 for prothrombin time determination.

Determinations of prothrombin time with the semiautomatic fibrometer and with a more automated machine (Electra 600) were compared in regard to reproducibility, accuracy, and speed. Prothrombin times determined for replicate samples with the two machines showed a correlation coefficient of 0.98, but the Electra 600 sensed the clot 0.5 seconds before the fibrometer. The overall coefficients of variation for multiple tests in the normal therapeutic and elevated ranges of prothrombin time were 3.5% for the fibrometer and 2.0% for the Electra 600. The average technician working time was 60% shorter with the fully automated machine than with fibrometer. It is concluded that the automated machine was more accurate and more rapid in determining prothrombin time.