Reagent kit for detecting lupus anticoagulant and method of determining presence or absence of lupus anticoagulant

A method of determining the presence or absence of lupus anticoagulant comprising steps of:

• providing a first specimen and a second specimen, both of which are taken from a same subject;
• mixing the first specimen with a first clotting time-measuring reagent containing manganese salt, phospholipid and an activator for causing coagulation in vitro selected from the group consisting of ellagic acid, kaoline cerite, and silica, and a third clotting time-measuring reagent containing calcium salt to measure a first clotting time;
• mixing the second specimen with a second clotting time-measuring reagent which contains manganese salt, phospholipid and an activator for causing coagulation in vitro selected from the group consisting of ellagic acid, kaoline, cerite and silica, and a fourth clotting time-measuring reagent containing calcium salt to measure a second clotting time, wherein a concentration of the manganese salt in the second clotting time-measuring reagent is lower than that of the first clotting time-measuring reagent or the second clotting time-measuring reagent does not contain manganese salt;
• and
• determining whether lupus anticoagulant is contained in the subject by determining whether the first clotting time is shortened relative to the second clotting time as an indicator of the existence of lupus anticoagulant.