Accurate analyte measurements for electrochemical test strip based on sensed physical characteristic(s) of the sample containing the analyte
Various embodiments for methods and systems that allow for a more accurate analyte concentration with a biosensor by determining at least one physical characteristic of the sample containing the analyte and deriving one of a batch slope, sampling time, or combinations thereof to attain accurate glucose concentration.
1. A method of demonstrating increased accuracy of a test strip, the method comprising:
providing a batch of test strips;
introducing a referential sample containing a referential concentration of an analyte to each test strip of the batch of test strips to initiate a test sequence;
reacting the analyte with a reagent on each test strip to cause a physical transformation of the analyte;
determining a physical characteristic of the referential sample;
deriving a defined batch slope for the batch of test strips based on the determined physical characteristics of the referential sample for selected test strips from the batch of test strips;
determining an approximate analyte concentration of the referential analyte concentration as being in one of a low glucose range, a medium glucose range or a high glucose range;
determining a sampling time point based on the approximate analyte concentration of the referential analyte concentration, the determined sampling time point being selected as a first sampling time point responsive to the approximate analyte concentration being in the low glucose range, a second sampling time point responsive to the approximate analyte concentration being in the medium glucose range, and a third sampling time point responsive to the approximate analyte concentration being in the high glucose range;
sampling an electrical output of the referential sample at the determined sampling time point during the test sequence;
calculating an analyte concentration based on the defined batch slope, the determined sampling time point and sampled electrical output to provide for a final analyte concentration value for each test strip of the batch of test strips such that at least 95% of the final analyte concentration values of the batch of test strips are within ±15% of the referential analyte concentration.
2. The method of claim 1 , in which the determining comprises applying a first signal to the sample to measure the physical characteristic of the sample.
3. The method of claim 2 , in which the sampling comprises driving a second signal to the sample.
4. The method of claim 3 , in which the applying of the first signal and the driving of the second signal is in sequential order.
5. The method of claim 3 , in which the applying of the first signal overlaps with the driving of the second signal.
6. The method of claim 2 , in which the applying of the first signal comprises directing an optical signal to the sample so that a physical characteristic of the sample is determined from an output of the optical signal.
7. The method of claim 2 , in which the applying of the first signal comprises directing an alternating signal to the sample so that a physical characteristic of the sample is determined from an output of the alternating signal.
8. The method of claim 2 , in which the applying of the first signal comprises driving first and second alternating signals at different respective frequencies in which a first frequency is lower than the second frequency.
9. The method of claim 8 , in which the first frequency is at least one order of magnitude lower than the second frequency.
10. The method of claim 8 , in which the first frequency comprises any frequency in the range of about 10 kHz to about 250 kHz.
11. The method of claim 1 , in which the physical characteristic comprises at least one of viscosity, hematocrit, temperature, and density of the sample, or combinations thereof.
12. The method of claim 1 , in which the physical characteristic comprises hematocrit and the analyte comprises glucose.
13. The method of claim 1 , in which the deriving comprises calculating a batch slope from an equation of the form:
x=aH 2 +bH+c
where
x represents a derived batch slope from the deriving step;
H represents the measured, determined or estimated physical characteristic of the sample;
a represents about 1.4e−6,
b represents about −3.8e−4,
c represents about 3.6e−2.
14. The method of claim 13 , in which the calculating of the analyte concentration comprises utilizing an equation of the form:
G
0
=
[
I
E
-
Intercept
x
]
where
G 0 represents an analyte concentration
I E represents, or is, a signal (value or measurement; proportional to analyte concentration) measured at a predetermined or specified sampling time;
Intercept represents a calibration parameter for a batch of biosensors;
x represents a derived batch slope from the deriving step.
15. The method of claim 14 , in which the predetermined time is about 2.5 seconds after a start of the test sequence.