Furthermore, given that LAC interferes with in vitro clotting-based assays, esoteric chromogenic assays
should be used in this setting to measure factor VIII activity and the strength of the factor VIII inhibitor, which can provide essential guidance regarding patient management.
Qualitative PT (a) PT (a) assessment of NO AC levels Quantitative Chromogenic anti-factor Chromogenic assessment of NO AC Xac anti-factor Xa (c) levels Abbreviations: aPTT, activated partial thromboplastin time; dTT, dilute thrombin time; ECA, ecarin chromogenic assay
; ECT, ecarin clotting time; FDA, US Food and Drug Administration; INR, international normalized ratio; N/A, not applicable; NOAC, novel oral anticoagulant; PT, prothrombin time; TT, thrombin time.
This method uses titration to a given concentration of heparin using either the protamine sulfate neutralization technique or a factor Xa inhibition chromogenic assay
. The CAP conference XXXI on lab monitoring of UFH therapy recommends that the most appropriate method for determination of the heparin therapeutic range is through direct comparison of the APTT assay with heparin concentrations from samples of stabilized patients receiving heparin.
However, such fragments may still possess significant anti-Xa activity and thus be detected via the chromogenic assay
In addition to ProC Global, samples were assayed for FV Leiden (Coatest APC Resistence, Chromogenics, 1+4 dilution of samples in FV-deficient plasma), protein C activity (chromogenic assay
, Boehringer Mannheim), and protein 5 activity (clotting test, Boehringer Mannheim).
(76,82) Nowadays, three major methods are used for the measurement of factor VIII, namely one-stage methods, classical two-stage assay and chromogenic assays
(28) As an alternative to clotting based tests, the chromogenic assays
are specific, but currently lack widespread availability.