A comparison of five manually operated coagulation instruments.

The results of activated partial thromboplastin time (APTT) and prothrombin time (PT) determinations on the single-channel Coag-a-Mate, Coagulyzer Jr., Clotek, Electra 650, and Fibrometer instruments were compared with regard to precision, day-to-day reproducibility of results, and accuracy. There was no significant difference among the machines when PT was analyzed. In the APTT study, the single-channel Coag-a-Mate had the best overall precision (coefficient of variation 2 to 4%), while the Coag-a-Mate and the Electra 650 had the best day-to-day reproducibility (coefficient of variation 2 to 5%). The comparison study indicated good correlation (r greater than or equal to 0.95) between the reference instrument (Bio/Data CA-15) and the single-channel Coag-a-Mate, Electra 650, and Clotek. The correlation for the Coagulyzer Jr. was also quite good (r = 0.95), but it could not detect some of the clots detected by the other machines. The Fibrometer showed significantly poorer correlation (r = 0.87) when compared with the other instruments.