The Influence of Sampling Technique on ACT Plus ® Results

The manufacturer of the ACT Plus Automated Coagulation Timer, Medtronic
Inc., recommends that test cartridges be prewarmed and the activating
reagent resuspended (tapped/ mixed) before patient testing. In a busy
clinical environment, these recommendations may be overlooked or
disregarded. In this study, the impact of sampling technique on ACT Plus
test results was investigated. In Series 1, two test cartridges were
split into four individual chambers. Two ACT Plus machines were used,
allowing for three separate comparisons to be made. The sample results
from test Chambers 2 (cold/tapped), 3 (warmed/ not tapped), and 4
(cold/not tapped) were compared individually against the result from
test Chamber 1, the recommended technique (warm/tapped). In Series 2,
the manufacturer’s recommendations were tested using a single double
cartridge (warm/ tapped). Results were interpreted using the
Bland-Altman method of analysis. The prewarming and tapping of
cartridges before use independently influenced the agreement of results
when compared with cartridges that were not prewarmed and tapped. Each
factor (temperature and mixing) when excluded was found to affect the
standard deviation and decrease the agreement of results. By following
the manufacturer’s recommendations to standardize the sampling
technique, ACT Plus test results are more accurate.