Method for correcting erroneous results of measurement in biosensors and apparatus using the same

• US 8,343,331 B2
• Filed: 09/26/2008
• Issued: 01/01/2013
• Est. Priority Date: 09/27/2007
• Status: Active Grant

• Current Assignee: Philosys Co., Ltd.
• Original Assignee: Philosys Co., Ltd.
• Inventors: Choi, In Hwan
• Primary Examiner(s): Ball, J. Christopher
• Assistant Examiner(s): DIETERLE, JENNIFER M
• Application Number:
  US12/670,900
• Publication Number:
  US 20100206749A1
• Time in Patent Office: 1,558 Days
• Field of Search: 204400-40315, 205/777.5, 205/787, 205/792, 205/775, 205/789, 600309-367, 422/68, 422/68.1, 435/14
• US Class Current: 205/777.5
• CPC Class Codes: G01N 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771

Abstract

Disclosed herein is a method of correcting erroneous measurement results in a biosensor. The method includes the steps of: (a) applying a first voltage from a voltage generator 12 to a test strip 10 when a blood sample is applied on the test strip 10, and measuring an electric current generated from the test strip within one second of applying the first voltage by a microcontroller unit (MCU), and then calculating a hematocrit value of the blood sample using the measured electric current value! (b) applying a second voltage from the voltage generator to the test strip after calculating the hematocrit value of the blood sample, and measuring an electric current generated from the test strip within a predetermined time of applying the second voltage, and then calculating a glucose level using the measured electric current value; and (c) correcting the glucose level in (b) by using the calculated hematocrit value in (a).

Claims

1. A method of correcting erroneous measurement results in a biosensor, the method comprising the steps of:

(a) applying a first voltage from a voltage generator 12 to a test strip 10 when a blood sample is applied on the test strip 10, and measuring an electric current generated from the test strip within one second of applying the first voltage by a micro controller unit (MCU), and then calculating a hematocrit value of the blood sample using the measured electric current value;

(b) applying a second voltage from the voltage generator 12 to the test strip 10 after calculating the hematocrit value of the blood sample, and measuring an electric current generated from the test strip within a predetermined time of applying the second voltage, and then calculating a glucose level using the measured electric current value; and

(c) correcting the glucose level in (b) by using the calculated hematocrit value in (a),

wherein

the step of calculating of the hematocrit value of the blood sample in (a) comprises calculating a hematocrit value using the following Equation 2, the following Equation 2 being obtained by preparing blood samples respectively having low, medium and high glucose levels corresponding to low, medium and high hematocrit values, measuring an electric current at 500 msec for each blood sample, and by estimating a slope and an intercept with X-axis representing an electric current, and Y-axis representing hematocrit;

Hct(%)=m*I_0.5t+n 

 

(Equation

     2)

wherein, I_0.5t is a measured current value at 500 msec, and m and n are experimentally determined coefficients; and

the step of correcting of the glucose concentration value in (c) is performed by using the following Equation 3;

Glc2′

=Glc2*γ

+δ

 

 

(Equation

     3)

wherein,

γ

=(45−

Hct(%))*0.075, δ

=1;

Glc2 is a measured glucose value before correcting a hematocrit effect; and

Glc2′

is a calculated glucose value after correcting a hematocrit effect.

2. The method of claim 1, wherein said electric current generated from the test strip within one second is an electric current generated from the test strip within 450 to 530 msec.

3. The method of claim 1, wherein the step of calculating of the hematocrit value of the blood sample in (a) is performed by using the following Equation 6 if the blood sample is determined to be from venous blood and a glucose level thereof is less than 150 mg/dL, by using the following Equation 7 if the blood sample is determined to be from venous blood and a glucose level thereof is in a range of from 150 mg/dL to 250 mg/dL, or by using the following Equation 8 if the blood sample is determined to be from venous blood and a glucose level thereof is greater than 250 mg/dL:

1) if a glucose level of the blood sample is less than 150 mg/dL

Hct (%)=−

0.8788*I_0.5t+119 

 

(Equation

     6)

2) if a glucose level of the blood sample is in a range of from 150 mg/dL to 250 mg/dL

Hct (%)=−

0.8514*I_0.5t+122 

 

(Equation

     7)

3) if a glucose level of the blood sample is greater than 250 mg/dL

Hct (%)=−

0.6426*I_0.5t+105 

 

(Equation

     8)

wherein,

I_0.5t is a measured current value at 500 msec, and a unit thereof is 10<sup>−

5</sup> A and

the step of correcting of the glucose level value in (c) is performed by using the following Equation 3;

Glc2′

=Glc2*γ

+δ

 

 

(Equation

     3)

wherein,

γ

=(45−

Hct (%))*0.075, δ

=1,

Glc2 is a measured glucose value before correcting a hematocrit effect, and

Glc2′

is a calculated glucose value after correcting a hematocrit effect.

4. The method of claim 1, wherein the step of calculating of the hematocrit value of the blood sample in (a) is performed by using the following Equation 9 if the blood sample is determined to be from capillary blood and a glucose thereof is less than 150 mg/dL, by using the following Equation 10 if the blood sample is determined to be from capillary blood and a glucose level thereof is in a range of from 150 mg/dL to 250 mg/dL, or by using the following Equation 11 if the blood sample is determined to be from capillary blood and a glucose level thereof is greater than 250 mg/dL:

1) if a glucose level of the blood sample is less than 150 mg/dL

Hct (%)=−

0.8788*I_0.5t+184 

 

(Equation

     9)

2) if a glucose level of the blood sample is in a range of from 150 mg/dL to 250 mg/dL

Hct (%)=−

0.8514*I_0.5t+187 

 

(Equation

     10)

3) if a glucose level of the blood sample is greater than 250

Hct (%)=−

0.6426*I_0.5t+170 

 

(Equation

     11)

wherein, I_0.5t is a measured current value at 500 msec, and a unit thereof is 10<sup>−

5</sup> A, and

wherein the step of correcting of the glucose level value in (c) is performed by using the following Equation 3;

Glc2′

=Glc2*γ

+δ

 

 

(Equation

     3)

wherein,

γ

=(45−

Hct (%))*0.075, δ

=1;

Glc2 is a measured glucose value before correcting a hematocrit effect; and

Glc2′

is a calculated glucose value after correcting a hematocrit effect.

5. The method of claim 1, further comprising a step of correcting measurement results from an effect of humidity, wherein the step of correcting measurement results comprises the steps of:

applying a voltage from a voltage generator 12 to a test strip 10 before a blood sample is applied to the test strip 10;

converting an electric current generated through the test strip 10 to voltage and then converting an analogue signal of the converted voltage to a digital signal by an analog-to-digital (A/D) converter 13;

calculating a humidity value by the MCU 16; and

correcting the glucose level value using the calculated humidity value,

wherein the step of calculating a humidity value is performed by using the following Equation 12, and the step of correcting the glucose level value is performed by using the following Equation 5 with the calculated humidity value;

Humidity (%)=33.173*Inosample+2.885 

 

(Equation

     12)

wherein,

Inosample is a current value measured when the blood sample is not applied to the test strip;

Glc1′

=Glc1*α

+β

 

 

(Equation

     5)

wherein,

α

=(55−

Humidity (%))*0.005, β

=1;

Glc1 is a measured glucose value before correcting a humidity effect, and

Glc1′

is a calculated glucose value after correcting a humidity effect.