engleski

Is it possible to predict the degree of FVIII deficiency from APTT waveform analysis on Behring Coagulation Timer (BCT)

With modern coagulation instruments, every aPTT result is not just a number but a collection of photo-optical data in the form of reaction curve. In this study we have performed a quantitative aPTT waveform analysis in order to examine whether it was possible to detect the degree of FVIII deficiency using parameters from this analysis. We measured aPTT (Actin FS, Dade Behring) in 38 normal and 87 hemophilia A patients on BCT coagulation analyzer (Dade Behring), with two different evaluation modes: fixed absorbance (FA) and point of inflexion (PI), that determine clotting times at the onset and midpoint of coagulation, respectively. Additionally, we calculated delta-aPTT (DaPTT) as aPTT-PI minus aPTT-FA and aPTT-slope ratio (aPTTSR) as ratio between DaPTT and aPTT-FA. FVIII activity was measured by one-stage assay. FVIII inhibitor screen was performed and inhibitor concentrations determined, when needed. Hemophilia patients were further divided in 4 groups (H1-H4) according to FVIII activity, and into 2 groups according to the presence (I2) or absence (I1) of the inhibitor. Significant differences (p<0.05) were found in DaPTT and aPTTSR values between normal and hemophilia patients, as well as between H1 to H4 and I1 and I2 groups. In normal and hemophilia patients the obtained results (mean± ; SD) for DaPTT were 4.24± ; 1.11 and 20.03± ; 11.47, respectively, and for aPTTSR 0.16± ; 0.03 and 0.33± ; 0.14, respectively. Results in specific groups were as follows: group H1 (N=41, FVIII<0.01) DaPTT=29.48± ; 8.62, aPTTSR=0.44± ; 0.13 ; group H2 (N=12, FVIII=0.01-0.05) DaPTT=17.51± ; 5.87, aPTTSR=0.29± ; 0.09 ; group H3 (N=24, FVIII=0.05-0.30) DaPTT=10.25± ; 4.18, aPTTSR=0.23± ; 0.05 ; group H4 (N=10, FVIII=0.30-0.50) DaPTT=7.75± ; 1.19, aPTTSR=0.19± ; 0.04 ; group I1 (N=48) DaPTT=17.83± ; 12.19, aPTTSR=0.30± ; 0.14, group I2 (N=21) DaPTT=28.06± ; 6.61, aPTTSR=0.42± ; 0.13. Based on these results, DaPTT values >6.5 and >17.7 allowed distinguishing between normal and hemophilia patients (sensitivity 94.7%, specificity 100%), and between patients with and without inhibitors (sensitivity 95.5%, specificity 64.7%), respectively.

FVIII deficiency; inhibitors; waveform analysis

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