Mathematical Expressions of Measuring Curves for Concentration of Clotting Factors

Abstract

Conversion of coagulation time (t) to relative arbitrary substance concentration of coagulation factors(II + VII + X) abbreviated c_ra) was originally made from a measuring curve corresponding to the equation log t=a_a0 + a₁ log c_ra. Three more suitable equations are presented and tested for fit: t=A₀ + A₁/c_ra; t=B₀ + B₁/c_ra + B₂/c²_ra; log t=b₀ + b₁ log c_ra + b₂ (log c_ra)². Their suitability for the Simplastin®-A and Thrombotest® methods is also investigated. The last equation yields the best fit and replaces the errorprone reading of log-log curves by a calculation suitable for routine use.

Key Words:

• Blood coagulation tests
• calculation
• curve reading
• minicomputer
• prothrombin time