Method for determining lupus anticoagulant in a single coagulation reaction

A method for detecting a lupus anticoagulant in a reaction mixture, the method comprising the steps of:

• (i) preparing a reaction mixture by combining a plasma sample of a patient with a lupus anticoagulant-sensitive activated partial thromboplastin time (APTT) reagent, which reagent contains ellagic acid and phospholipids and leads to prolonged coagulation time measurements in lupus anticoagulant-containing samples compared to coagulation time measurements in normal, lupus anticoagulant-free samples in a reaction vessel, and starting the coagulation reaction,
• (ii) continuously measuring a measurement variable S of the reaction mixture over time, resulting in a function S(t) of time-dependent measurement values for the reaction mixture, and
• (iii) determining the coagulation time for the reaction mixture, characterized in that
• a) the maximum reaction velocity vmax and/or the maximum reaction acceleration amax of the function S(t) for the reaction mixture are determined,
• b) the absolute value of the difference between a first measurement value SB at the start of measurement and a second measurement value SE at the end of measurement (|DeltaS|) is ascertained for the reaction mixture, and
• c) a relative maximum reaction velocity vmax rel and/or a relative maximum reaction acceleration amax rel for the reaction mixture are determined using the following formulae:
• v
• max
• ⁢
• rel
• =
• v
• max
• /
• |
• Delta
• ⁢
• S
• |
• and
• ⁢
• a
• max
• ⁢
• rel
• =
• a
• max
• /
• |
• Delta
• ⁢
• S
• |
• ,
• respectively, and
• (iv) detecting the lupus anticoagulant in the reaction mixture when the coagulation time of the reaction mixture is prolonged compared to a predetermined reference value, and the relative maximum reaction velocity vmax rel value and/or the relative maximum reaction acceleration amax rel value for the reaction mixture are within a predetermined lupus anticoagulant-specific range of value(s) for the reaction mixture.