The relationship between the minimal and the 50% haemolytic dose in complement titrations.

The 50% spectrophotometric complement titration end-point (C'H50) was found to be more reproducible than the 100% end-point. The relationship of the 100% end-point (MHD) to the (C'H50) was 1:2, 5. The use of thrombin tubes induced clotting within 2 min and enabled the process of complement preparation to be completed well within 1 hour.