Prothrombin timer

• US 3,967,934 A
• Filed: 06/25/1971
• Issued: 07/06/1976
• Est. Priority Date: 06/13/1969
• Status: Expired due to Term

• Current Assignee: Technicon Instruments Corporation
• Original Assignee: Baxter Laboratories, Inc. (Baxter International Inc.)
• Inventors: Seitz, Lamont J., Bowen, John G.
• Primary Examiner(s): Scovronek, Joseph
• Application Number:
  US05/156,740
• Time in Patent Office: 1,838 Days
• Field of Search: 23/230 R, 23/230 B, 23/253 R, 23/259, 73/57, 73/59, 73/64.1
• US Class Current: 422/73
• CPC Class Codes: G01N 11/10 by moving a body within the material
• CPC Class Codes: G01N 33/4905 Determining clotting time of blood by chemical methods G01N33/86, C12Q1/54

Abstract

A system and method is provided which has the general capabilities of measuring the speed of coagulation, congealing or solidification of a fluid sample, and which has particular utility in the measurement of the time required by a sample under test to increase viscosity to a particular level. The system and method to be described is predicated on a viscosity principle, and it includes a movable magnetic member suspended in the fluid sample and which changes position when the sample achieves a predetermined degree of viscosity. The change in position of the aforesaid member is photoelectrically or electromagnetically detected, and the time at which the change occurs, is used in the determination of the time required, for example, for the sample to form a fibrin clot, in a blood or plasma sample or to effect a particular reaction causing solidification or congealing of the sample.

Claims

1. Apparatus for use in determining the prothrombin time of a blood sample comprising:

a container for holding the blood sample, a freely movable ferromagnetic member disposed in the container, a magnetic field source located near the container and forming a weak magnetic couple with the ferromagnetic member, means for producing relative movement between the ferromagnetic member and the container, the intensity of the magnetic field source being sufficient to prevent relative movement between the ferromagnetic member and the magnetic field source prior to clotting but insufficient to prevent relative movement between the ferromagnetic member and the magnetic field source on clotting due to an increase in the resistance to movement of the ferromagnetic member in the container imposed on the ferromagnetic member by the blood sample, and means for deriving a signal in response to relative movement between the ferromagnetic member and the magnetic field source, the signal signifying the end point in determining the prothrombin time.