engleski

Impact of different evaluation modes for the detection of clotting times on APTT results

Modern photo-optical coagulometers collect optical data over the entire course of clot formation, by monitoring changes in light absorbance or transmittance. By using different evaluation modes, they offer possibility to measure clot time at different points of clot formation. The aim of our study was to find out if there was a difference between aPTT results (n=104) obtained with different evaluation modes (fixed absorbance, drifting-baseline and point of inflexion) on Dade Behring coagulation analyzers BCS and BCT, by using Actin FS as aPTT reagent. Discrepant aPTT results were observed on all analyzed samples, being always longer with point of inflexion (mean value: 39.4 s, range: 20.5-99.1s) as compared with results obtained by using drifting-baseline (mean value: 33.3 s, range: 20.0-78.5 s) or fixed absorbance (mean value: 31.2 s, range: 19.0-80.8 s). Additionally, incorrect results were identified by visual inspection of reaction curves in 2 different situations. Extremely short aPTT results were obtained in 4 samples with fixed absorbance. Secondly, despite normal reaction curves in 5 samples, no clot result was measured by drifting mode. In all these cases, another 2 evaluation modes gave correct results. Differences between results obtained with different evaluation modes indicate the need to establish not only reagent-coagulometer specific, but also evaluation mode specific reference intervals. According to our experience we suggest verification of the reaction curve of all suspected results and, if needed, repeated testing with another evaluation mode.

evaluation mode; aPTT

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