SYSTEMS, DEVICES, AND METHODS FOR MEASURING WHOLE BLOOD HEMATOCRIT BASED ON INITIAL FILL VELOCITY
Methods for determining the hematocrit of a blood sample, and devices and systems used in conjunction with the same. The hematocrit value can be determined on its own, and further, it can be further used to determine a concentration of an analyte in a sample. In one exemplary embodiment of a method for determining the hematocrit value in a blood sample, a volume of blood is provided in a sample analyzing device having a working and a counter electrode. An electric potential is applied between the electrodes and an initial fill velocity of the sample into the device is calculated. The hematocrit of the blood, as well as a concentration of an analyte in view of the initial fill velocity can then be determined. Systems and devices that take advantage of the use of an initial fill velocity to determine hematocrit levels and make analyte concentration determinations are also provided.
1 . A method for determining a concentration of an analyte in a sample, the method comprising:
providing a sample including an analyte to a sample analyzing device having a working electrode and a counter electrode;
applying an electric potential between the working electrode and the counter electrode;
determining an initial fill velocity of the sample; and
calculating a concentration of the analyte in view of the initial fill velocity.
2 . The method of claim 1 , wherein determining an initial fill velocity further comprises:
measuring an initial current after applying the electric potential;
determining a level of hematocrit in the sample; and
reversing the electric potential between the working electrode and the counter electrode.
3 . The method of claim 2 , wherein calculating the concentration of the analyte further comprises computing the concentration based on the determined level of hematocrit.
4 . The method of claim 3 , further comprising measuring a change in current over a period of time following reversing the electric potential, wherein calculating a concentration of the analyte further comprises calculating the concentration of the analyte in view of the change in current over the period of time.
5 . The method of claim 3 , wherein the sample comprises whole blood, the method further comprising at least one of measuring a temperature of the whole blood or inferring a temperature of the whole blood.
6 . The method of claim 1 , wherein determining an initial fill velocity further comprises determining a rate of change in an optical signal to calculate the initial fill velocity.
7 . The method of claim 1 , wherein determining an initial fill velocity further comprises determining an initial current flow to determine the initial fill velocity.
8 . The method of claim 7 , wherein determining an initial current flow further comprises:
performing current measurements approximately every 10 milliseconds for at least approximately 50 milliseconds; and
calculating an average current based on the current measurements.
9 . The method of claim 1 , wherein determining an initial fill velocity further comprises determining an initial fill velocity directly after the sample enters a capillary space of the sample analyzing device.
10 . The method of claim 1 , wherein determining an initial fill velocity further comprises determining an initial fill velocity after the sample crosses into a region of a capillary space of the sample analyzing device where a detection signal is generated.
11 . The method of claim 1 , wherein the sample analyzing device comprises an immunosensor.
12 . The method of claim 3 , further comprising measuring a change in current over a period of time after reversing the electric potential, wherein calculating a concentration of the analyte further comprises calculating the concentration of the analyte in view of the change in current over the period of time.