[in Japanese]

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The kaolin clotting time (KCT) mixing test is most widely conducted in clinical laboratories for detecting the lupus anticoagulant in plasma of patients with the antiphospholipid syndrome. The negative control plasma used for this test has so far been prepared from pooled plasma derived from healthy volunteers in individual laboratories, and thus these control plasmas may not necessarily be equivalent in terms of the state of blood coagulation mechanism that could be activated during blood collection.
To see whether the blood coagulation mechanism is activated during blood collection, we tested the KCT, and measured the amount of the thrombin-antithrombin complex (TAT) in plasmas derived form blood collected into vacuum pipes at every one minute over 10 minutes consecutively. When the tourniquet had been applied upon blood collection, the KCT became shorter and the amount of TAT gradually increased in accordance with the time of tourniquet application, as prominently noted in three out of 9 samples. The increase of TAT in these samples was significantly high as compared with that in the samples collected without the tourniquet application.
These data indicate that the blood coagulation mechanism is certainly activated during blood collection under a long-term application of the tourniquet, and that falsely negative results are deduced from the tests, when such plasmas with activated blood coagulation are used as the control plasma for the presence of lupus anticoagulant. Thus, care must be taken to avoid the activation of blood coagulation during blood collection. Here we propose that the KCT test and measurement of TAT should be considered to exclude the plasmas with activated blood coagulation from pooled plasma to be used as the control for the detection of lupus anticoagulant.

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