Abstract: Improved methods and apparatus that make more accurate and reduces risk of filling reaction chambers of cartridge cells with blood samples to conduct blood coagulation tests of the type employing the plunger technique are disclosed. A cartridge holder is provided that secures a test cartridge in a fixed upright position and deflects the plunger flag of each cartridge cell to enable manual insertion of a blood dispenser deeply into the reaction chamber to fill the reaction chamber and avoid contamination of surfaces of the cartridge outside the reaction chamber. Preferably, the cartridge holder provides illumination of the reaction chamber during filling, so that the user can judge when the reaction chamber is properly filled with blood dispensed from the blood dispenser. The cartridge holder may incorporate image magnification to facilitate viewing of the reaction chamber as it is filled.