Method and apparatus for detecting a blood clot

• US 4,797,369 A
• Filed: 04/05/1985
• Issued: 01/10/1989
• Est. Priority Date: 04/05/1985
• Status: Expired due to Term

• Current Assignee: International Technidyne Corporation (Sphingotec GMBH)
• Original Assignee: International Technidyne Corporation (Sphingotec GMBH)
• Inventors: Mintz, Michael
• Primary Examiner(s): Marcus, Michael S.
• Application Number:
  US06/720,575
• Time in Patent Office: 1,376 Days
• Field of Search: 356/39, 324/446, 324/71.1, 422/73, 436/69, 436/150, 436/151
• US Class Current: 436/69
• CPC Class Codes: G01N 33/4905 Determining clotting time of blood by chemical methods G01N33/86, C12Q1/54

Abstract

A sample of whole blood or blood plasma is dispensed into two or more zones. The zones are separated and brought together repeatedly such that the blood sample is divided into multiple parts each associated with a zone. The parts are then rejoined into a single part and the process of separation continues. During the process, a liquid bridge between the separating parts is initially supported by surface tension but eventially collapses at the point of maximum zonal separation. When a fibrin clot is entrained within the rejoined part, it will align in a direction parallel to the direction of the relative motion between the zone. In this manner a thread appears between the parts as they are being separated. This thread is indicative of a clot which clot is capable of being detected by visual or electrical conductivity means. The apparatus depicted performs the above noted operations and automatically provides an output signal upon detection of the fibrin clot.

Claims

1. A method of detecting the formation of fibrin clots in whole blood or blood plasma comprising the steps of:

dispensing a sample of blood to be analyzed in a container,

moving a probe having a hydrophilic tip into said dispensed sample to cause a first part of said sample to adhere to said probe tip with a second part remaining in said container,

repeatedly moving said first part of said sample into said second part from a given fixed point at a given distance from said second part and out of said second part to repeatedly join and separate said first and second parts, a fluid bridge being formed between said parts by surface tension and during movement of said first part over a portion of said given distance away from said second part, said given distance being selected so that said fluid bridge collapses when said first part is separated from said second part by said given distance unless a fibrin clot is aligned and entrained within said bridge such that said clot connects said first part to said second part at said given distance,

applying an electrical potential between said parts when said first and second parts are separated at said given distance,

monitoring the electrical current between said first and second parts when said electrical potential is applied,

providing a signal when an electrical current is detected between said first and second parts indicative of the presence of an electrically conductive path between said first and second parts, said path comprising at least one fibrin clot simultaneously connected between both said first and second parts and entrained within said bridge when said first and second parts are separated at said given distance.

2. The method according to claim 1 including the further step of:

mixing a reagent with said blood sample prior to the step of repeatedly moving said first part of said sample into and out of said second part.

3. The method according to claim 1 and including the further step of:

determining the time that has elapsed between said signal, which is representative of said fibrin clot, and the addition of said sample into said container.

4. The method according to claim 3 including the further step of:

recording the results of said timing.

5. Apparatus for detecting the formation of fibrin clots in a whole blood or blood plasma sample, comprising:

a container housing having an internal hollow and having a hollow tubular member communicating with said internal hollow at a first end, with said hollow tubular member adapted to be inserted into a source of blood,

movable plunger means coupled to a second end of said container housing and including a probe means having a hydrophilic probe tip positioned within said internal hollow;

a partition means coupled to said movable plunger means and positioned within said hollow to cause a predetermined volume of blood sample to enter said hollow of said container via said tubular member when said plunger means is moved upwardly from said container housing,

means coupled to said plunger means for positioning said probe tip a given distance from said first end of said container to cause said tip to be positioned at a given fixed point from said predetermined volume of blood sample in said hollow and to thereafter repeatedly move said probe tip in and out of said sample to cause a given blood sample to adhere to said tip and to move from said fixed point with said distance selected to allow a surface tension bridge to form between said probe tip end and said sample whereby if a fibrin clot is entrained within said bridge said clot connects said plunger means via said probe tip to said sample and if a clot is not entrained said bridge will collapse when said probe tip is at said fixed point,

detecting means coupled between said plunger means and said tubular member means and responsive to said connection to provide an indication of the presence of said clot when said probe tip is separated from said sample at said given distance.

6. The apparatus according to claim 5 further including a rupturable membrane means containing a blood reagent and located within said internal hollow and positioned to coact with said partition means when moved upwardly to rupture said membrane means to discharge said reagent into said blood sample.

7. In an apparatus for detecting the formation of fibrin clots in a whole blood or blood plasma sample, said apparatus of the class including a movable probe positioned to move in and out of a blood sample contained in a blood reservoir and to provide an indication when a blood clot connects said probe to said reservoir, the improvement in combination therewith, comprising:

a hydrophilic probe tip connected to the end of said movable probe and positioned so that when said probe tip is moved into said reservoir said tip causes a blood sample to adhere thereto, with said tip having said adhered sample restrained to move away from said reservoir at a given selected distance so that a fluid bridge is formed between said adhered sample and said reservoir during probe movement where said bridge will collapse at said given distance unless a fibrin clot is entrained and aligned within said bridge to cause said probe tip to therefore be connected to said reservoir solely by said entrained clot and independent of any clots formed in said reservoir, means for detecting the presence of said entrained fibrin clot which connects said probe tip to said reservoir, and activatable timing means which is activated when said sample adheres to said probe tip for beginning a time period and for terminating said time period when said fibrin clot connects said reservoir to said probe tip.

8. The apparatus according to claim 7 in which said means for detecting the presence of said fibrin clot comprises means for measuring the electrical conductance between said probe tip and said reservoir when separated by said given distance.

9. The apparatus according to claim 7 wherein said means for detecting the presence of said clot includes electrical conductivity measuring means having one input terminal coupled to said probe and a second input terminal connected to said reservoir.

10. An apparatus for detecting the formation of fibrin clots in a whole blood or blood plasma sample, comprising:

a probe having a hydrophilic end to form a surface to which a sample of blood will adhere indicative of a first zone of blood,

means for positioning said probe end a given distance from a sample of blood indicative of a second zone,

means for positioning relative motion between said probe end and said sample to cause said probe end to move in and out of said sample to cause blood to adhere to said probe end indicative of said first zone and to continue said motion to repeatedly join and separate said first and second zones at said given distance to form a fluid bridge from said first and second blood zone samples which bridge is formed by surface tension between said zones and which bridge will collapse at said given distance when a fibrin clot is not entrained and aligned within said bridge, with an entrained fibrin clot serving to connect said zones together at said given distance,

means for measuring the electrical conductance between said zones when said zones are separated by said given distance,

means for generating a signal when an electrical conductance is detected indicative of an electrically conductive path between said zones manifesting the presence of an entrained fibrin clot within said fluid bridge and aligned between said zones to electrically connect said first zone to said second zone,

activatable timing means which is activated when said sample first adheres to said probe and which is terminated upon generation of said signal indicative of said electrically conductive path.