Apparatus and method for analytical determinations

• US 6,794,877 B2
• Filed: 07/31/2002
• Issued: 09/21/2004
• Est. Priority Date: 07/31/2002
• Status: Expired due to Fees

• Current Assignee: Easydx Inc.
• Original Assignee: International Technidyne Corporation (Sphingotec GMBH)
• Inventors: Blomberg, Scott Everett, Sin, Kee Van, Ott, Brian Anthony
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): NGUYEN, HOAI AN D
• Application Number:
  US10/210,661
• Publication Number:
  US 20040021469A1
• Time in Patent Office: 783 Days
• Field of Search: 324/434, 324/426, 324/425, 324/439, 324/71.1, 324/692, 324/722, 204/400, 204/402, 204/406, 204/415, 205/778, 205/781.5, 422/44, 422/56, 422/61, 422/67, 422/82.01, 422/82.02, 436/16, 436/63, 436/66, 436/68, 436/178
• US Class Current: 324/434
• CPC Class Codes: G01N 33/491 by separating the blood components G01N15/05 takes precedence

Abstract

An apparatus and method for measuring conductance are provided. The method and apparatus are particularly well adapted for use with a removable or replaceable cartridge in a blood analysis system. The apparatus generally involves providing a system having a first, unfiltered, conductance measurement cell and a second, filtered, conductance measurement cell. The preferred method involves relating values measured in the two cells for a whole blood sample and for a known calibrant together, to obtain a value, for example hematocrit, for the unknown whole blood sample.

Claims

1. A sample analysis cartridge comprising:

(a) a substrate defining a top surface and a bottom surface;

(b) a liquid sample inlet near the top surface of the substrate; and

(c) a conductance measurement arrangement mounted on the substrate and including;

(i) a first, unfiltered, conductance measurement cell in fluid flow communication with the liquid sample inlet; and

(ii) a second, filtered, conductance measurement cell in fluid flow communication with the liquid sample inlet.

2. A sample analysis cartridge according to claim 1 wherein:

(a) the conductance measurement arrangement is a hematocrit measurement arrangement; and

,

(b) the second, filtered, conductance measurement cell is a red blood cell filtered conductance measurement cell.

3. A sample analysis cartridge according to claim 2 including:

(a) at least one, non-hematocrit, analytical sensor in fluid flow communication with the liquid sample inlet.

4. A sample analysis cartridge according to claim 2 wherein:

(a) the second, red blood cell filtered, conductance measurement cell comprises two spaced electrodes shielded by filter material.

5. A sample analysis cartridge according to claim 4 wherein:

(a) the filter material comprises a hydrogel.

6. A sample analysis cartridge according to claim 4 wherein:

(a) the filter material comprises a microporous membrane.

7. A sample analysis cartridge according to claim 4 wherein:

(a) the filter material comprises a slit dielectric material.

8. A sample analysis cartridge according to claim 4 wherein:

(a) the spaced electrodes within the second conductance measurement cell each comprise a gold electrode;

the two spaced electrodes of the second conductance measurement cell being spaced apart from one another by a distance of no greater than 0.127 mm.

9. A sample analysis cartridge according to claim 5 wherein:

(a) the filter material comprises a PVA hydrogel.

10. A sample analysis cartridge according to claim 5 wherein:

(a) the cartridge defines a perimeter area of no greater than 80 sq. cm.

11. A sample analysis cartridge according to claim 6 wherein:

(a) the filter material comprises a microporous polycarbonate membrane.

12. A sample analysis cartridge according to claim 10 wherein:

(a) the first, unfiltered, conductance measurement cell comprises two spaced electrodes.

13. A sample analysis cartridge according to claim 10, wherein:

(a) the hematocrit measurement arrangement is configured for an operational sample volume of no greater than 200 μ

l.

14. A sample analysis cartridge according to claim 12, wherein:

(a) the two spaced electrodes within the first, unfiltered, conductance measurement cell each comprise a gold electrode.

15. A sample analysis cartridge, comprising:

a liquid sample inlet;

a conductance measurement arrangement including;

(i) a first, unfiltered, conductance measurement cell that is a hematocrit measurement arrangement in fluid flow communication with the liquid sample inlet; and

(ii) a second, filtered, conductance measurement cell that is a red blood cell filtered conductance measurement cell in fluid flow communication with the liquid sample inlet and comprising two spaced electrodes shielded by filter material comprising a hydrogel;

wherein the cartridge defines a perimeter area of no greater than 80 sq. cm; and

wherein the first unfiltered, conductance measurement cell includes a single electrode, which is operated to measure an unfiltered conductance value by use of an electrode in the second, filtered, conductance measurement cell.

16. A method of evaluating hematocrit, comprising:

(a) measuring conductance of an unknown whole blood sample in a hematocrit measurement system including;

(i) a substrate defining a first surface and a second surface opposed to the first surface;

(ii) a first, unfiltered, conductance measurement cell on the first surface to provide a measurement value C_B; and

(iii) a second, red blood filtered, conductance measurement cell on the first surface to obtain a measurement value C_p; and

(b) correlating the conductance measurements C_B and C_p to determine a hematocrit value for the whole blood sample.

17. A method according to claim 16 including steps of:

(a) measuring conductance of a known calibrant in;

(i) the first, unfiltered, conductance measurement cell to obtain a conductance measurement value C_C; and

,

(ii) the second, red blood filtered, conductance measurement cell to obtain a conductance measurement value C_CF;

(b) wherein said step of correlating comprises correlating the conductance measurements C_B, C_p, C_C and C_CF together to determine a hematocrit value for the unknown whole blood sample.

18. A method according to claim 17 wherein:

(a) said step of correlating comprises;

(i) calculating a value of R_B from the formula;

R_B=C_B/C_C;

(ii) calculating a value of R_p from the formula;

R_p=C_p/C_CF; and

(iii) relating R_B to R_p to determine a hematocrit value for the unknown whole blood sample.

19. A method according to claim 18 wherein:

(a) said step of relating R_B to R_p comprises;

(i) calculating R_G according to the formula R_G=R_B/R_P; and

(ii) determining hematocrit by comparing R_G to an R_G function previously established using standards.

20. A method according to claim 19 wherein:

(a) said step of determining hematocrit by comparing R_G comprises determining hematocrit according to the formula;