Apparatus and method for analytical determinations

• US 20040021469A1
• Filed: 07/31/2002
• Published: 02/05/2004
• Est. Priority Date: 07/31/2002
• Status: Active Grant

• Current Assignee: Easydx Inc.
• Original Assignee: Diametrics Medical, Inc. (Allegro Biodiesel Corp.)
• Inventors: Anthony Ott, Brian, Blomberg, Scott Everett, Sin, Kee Van
• Granted Patent: US 6,794,877 B2
• Time in Patent Office: Days
• 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 liquid sample inlet; and

,

(b) a conductance measurement arrangement 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 wherein:

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

4. A sample analysis cartridge according to claim 3 wherein:

(a) the filter material comprises a hydrogel.

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

(a) the filter material comprises a PVA hydrogel.

6. A sample analysis cartridge according to claim 3 wherein:

(a) the filter material comprises a microporous membrane.

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

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

8. A sample analysis cartridge according to claim 3 wherein:

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

9. A sample analysis cartridge according to claim 3 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.

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

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

11. 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.

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 12 wherein:

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

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

(a) 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.

15. 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.

16. A method of evaluating hematocrit;

said method including steps of;

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

(i) a first, unfiltered, conductance measurement cell to provide a measurement value C_B; and

,

(ii) a second, red blood filtered, conductance measurement cell 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 unknown 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;

Hematocrit=R_G(C1)+C2

wherein C1 and C2 are constants emperically derived for the hematocrit measurement system.