Analysis techniques for measuring glycated hemoglobin in undiluted blood samples
View Patent ↗Electrochemical test sensors and analysis methods are described that reduce or eliminate the pre-treatment or dilution of blood samples prior to HbA1c analysis. Thus, a blood sample obtained from a blood draw or phlebotomy may be introduced to the electrochemical test sensor for HbA1c analysis. The described test sensors immobilize or deactivate incompatible reagents, enzymes, and antibodies so they do not substantially interfere with each other during the analysis. The test sensors also use heat to catalyze reactions that otherwise would proceed at too slow of a rate to be practical.
1. A method of determining a corrected glycated hemoglobin concentration of an undiluted whole blood sample, the method comprising:
introducing an undiluted whole blood sample to a test sensor;
applying a potential to at least two electrical conductors of a hematocrit flow path;
determining an output current responsive to a hematocrit content of the sample;
applying a potential to a total hemoglobin working and counter electrode pair;
determining an output current from the total hemoglobin working and counter electrode pair responsive to a total hemoglobin concentration of the sample;
applying a potential to a glycated hemoglobin working and counter electrode pair;
determining an output current from the glycated hemoglobin working and counter electrode pair responsive to a glycated hemoglobin concentration of the sample; and
determining a corrected glycated hemoglobin concentration of the sample from the output currents, the output currents determined from
the hematocrit flow path,
the total hemoglobin working and counter electrode pair, and
the glycated hemoglobin working and counter electrode pair.
2. The method of claim 1 , where the applying the potential to at least two electrical conductors of the hematocrit flow path includes applying the potential to at least four electrical conductors of the hematocrit flow path and the determining the output current responsive to the hematocrit content of the sample includes determining at least three timing values from the at least four electrical conductors, the at least three timing values responsive to an entry rate of the sample through the test sensor.
3. The method of claim 2 , further comprising determining a value responsive to sample viscosity from the at least three timing values.
4. The method of claim 1 where the applying the potential to at least two conductors of the hematocrit flow path includes applying the potential to a hematocrit working and counter electrode pair and the determining the output current responsive to the hematocrit content of the sample includes determining an output current from the hematocrit working and counter electrode pair.
5. The method of claim 4 , where the output current determined from the hematocrit working and counter electrode pair is responsive to the electrical conductivity of the sample.
6. The method of claim 1 , further comprising before applying the potential to the total hemoglobin working and counter electrode pair, contacting the sample with a first chemical reaction zone and a pH adjustment zone.
7. The method of claim 6 , where the contacting the sample with the first chemical reaction zone lyses red blood cells in the sample and reduces lysate interference in the corrected glycated hemoglobin concentration determined from the sample.
8. The method of claim 6 , where the contacting the sample with the pH adjustment zone alters the pH of the sample.
9. The method of claim 1 , further comprising before applying the potential to the glycated hemoglobin working and counter electrode pair, contacting the sample with a first chemical reaction zone, a second chemical reaction zone, a pH adjustment zone, and an enzyme.
10. The method of claim 9 , where the contacting the sample with the second chemical reaction zone reduces the length of at least one peptide chain in the sample.
11. The method of claim 1 , where the contacting the sample with the enzyme produces an electrochemically active species having a concentration in the sample responsive to a glycated hemoglobin concentration of the sample.
12. The method of claim 1 , further comprising heating the total hemoglobin working and counter electrode pair and the glycated hemoglobin working and counter electrode pair to a temperature from 35 to 54 degrees Celsius before applying the potential to the total hemoglobin working and counter electrode pair and the glycated hemoglobin working and counter electrode pair, respectively.
13. The method of claim 1 , further comprising
applying a potential to an electrochemical background working and counter electrode pair;
determining an output current from the electrochemical background working and counter electrode pair responsive to an electrochemical background of the sample, where the determining the corrected glycated hemoglobin concentration of the sample from the output currents includes at least one current determined from the electrochemical background working and counter electrode pair.
14. The method of claim 13 , further comprising before applying the potential to the electrochemical background working and counter electrode pair, contacting the sample with a first chemical reaction zone, a second chemical reaction zone, and a pH adjustment zone.
15. The method of claim 13 , where the electrochemical background working and counter electrode pair lack an enzyme capable of producing an electrochemically active species.
16. The method of claim 13 , further comprising heating the electrochemical background working and counter electrode pair to a temperature from 35 to 54 degrees Celsius before applying the potential to the electrochemical background working and counter electrode pair.
17. The method of claim 1 , further comprising
applying a potential to an endogenous glycated hemoglobin background working and counter electrode pair;
determining an output current from the endogenous glycated hemoglobin background working and counter electrode pair responsive to an endogenous glycated hemoglobin background of the sample, where the determining the corrected glycated hemoglobin concentration of the sample from the output currents includes at least one current determined from the endogenous glycated hemoglobin background working and counter electrode pair.
18. The method of claim 17 , further comprising before applying the potential to the endogenous glycated hemoglobin background working and counter electrode pair, contacting the sample with a first chemical reaction zone, a pH adjustment zone, and an enzyme.
19. The method of claim 17 , further comprising heating the endogenous glycated hemoglobin working and counter electrode pair to a temperature from 35 to 54 degrees Celsius before applying the potential to the endogenous glycated hemoglobin background working and counter electrode pair.
20. The method of claim 18 , where the contacting the sample with the enzyme produces an electrochemically active species having a concentration in the sample responsive to a glycated hemoglobin concentration of the sample.
21. The method of claim 1 , where the determining the corrected glycated hemoglobin concentration of the sample includes determining a percent glycated hemoglobin to total hemoglobin value from the output currents determined from the glycated hemoglobin working and counter electrode pair and the total hemoglobin working and counter electrode pair, respectively.
22. The method of claim 21 , where the determining the corrected glycated hemoglobin concentration of the sample includes correcting the percent glycated hemoglobin to total hemoglobin value with the output currents determined from the hematocrit flow path.