GB1270416A - An improved method and apparatus for determining blood clotting time - Google Patents

Abstract

1,270,416. Determining blood clotting time. H. P. O. UNGER. 7 July, 1969, No. 34233/69. Heading G4H. [Also in Division G1] In an apparatus for determining the clotting time of a blood sample with which a reagent has been mixed, which apparatus is adapted to periodically tilt a container containing the mixture to a position in which the mixture if still fluid will cause a pulse to be produced, a timer started when the reagent is added is stopped automatically upon detection of a change in the pulsating output of the detector. In the form shown an elongated block 25 which extends in a direction normal to the plane of the figure and holds a plurality of sample tubes 13 in recesses is stepped in a direction along its length to bring the tubes one by one into the path of light between a source 15 and photocell 16 both mounted on a second block 10. Between each step of the block 25, a selfreplenishing syringe-type pipette 19 drops a quantity of reagent (such as a thromboplasticcalcium solution) into the blood sample already in the tube in the light path, starts a timer in the form of a counter-printer 20 driven by clock pulses, and energizes a mechanism to rock the assembly comprising the blocks 10 and 25, the tubes 13, the source 15 and the detector 16 repetitively from the position shown to a position in which the tubes are inclined along the direction 30. For each rocking movement, the mixture if still fluid flows into the light path producing an output pulse. The resulting pulsating output is fed to a threshold detector. The square wave output from the threshold detector is fed to a gating circuit which terminates advancement of the timer when the pulse train ceases, becomes delayed in phase or changes in unspecified manner due to clothing of the mixture. When this occurs the assembly is rocked once in the other direction to cause the printer to print the time taken to clotting to be printed on a card 29 in a holder 28 on the block 25. The timer is reset and the block 25 stepped to repeat the above for the next sample. The tubes may be of plastics material and may be coated internally with a hydrophilic substance such as polyoxyethylene sorbitan monooleate.