Patent AU-2012340500-B2 (AU)
Title: Accurate analyte measurements for electrochemical test strip based on multiple discrete measurements defined by sensed physical characteristic (s) of the sample containing the analyte
Inventor: MALECHA MICHAEL
IPC: G01N33/00
Filed: 2012-12-28
Granted: 2015-09-17
Abstract: (12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) I CORRECTED VERSION (19) World Intellectual Property Organization International Bureau (10) International Publication Number (43) International Publication Date W O 2013/098564 A9 4 July 2013 (04.07.2013) W I POI P CT (51) International Patent Classification: (74) Agents: BRUNNER, John Michael Owen et al.; Carp G01N27/327(2006.01) maels & Ransford, One Southampton Row, London WC 1 B (21) International Application Number: 5HA (GB). PCT/GB2012/053277 (81) Designated States (unless otherwise indicated, for every kind of national protection available): AE, AG, AL, AM, (22)28 December 2012 (28.12.2012) AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, (25) Filing Language: English DO, DZ, EC, EE, EG, ES, Fl, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IS, JP, KE, KG, KM, KN, KP, (26) Publication Language: English KR, KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, (30) Priority Data: ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, 61/581,087 29 December 2011 (29.12.2011) US NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, 61/581,089 29 December 2011 (29.12.2011) US RW, SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, 61/581,099 29 December 2011 (29.12.2011) US TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, 61/581,100 29 December 2011 (29.12.2011) US ZM, ZW. 61/654,013 31 May 2012 (31.05.2012) US (84) Designated States (unless otherwise indicated, for every (71) Applicant: LIFESCAN SCOTLAND LIMITED kind of regional protection available): ARIPO (BW, GH, [GB/GB]; Beechwood Park North, Inverness, i- GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, SZ, TZ, verness-shire IV2 3ED (GB). UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, (72) Inventor: MALECHA, Michael; An Caorann, Corry EE, ES, Fl, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, Road, Muir of Ord, Inverness-shire IV6 7TL (GB). MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, [Continued on next page] (54) Title: ACCURATE ANALYTE MEASUREMENTS FOR ELECTROCHEMICAL TEST STRIP BASED ON MULTIPLE DISCRETE MEASUREMENTS DEFINED BY SENSED PHYSICAL CHARACTERISTIC(S) OF THE SAMPLE CONTAINING THE ANALYTE (57) Abstract: Various embodiments that allow for a more Second Transient Signal accurate analyte concentration by determining at least one 200- physical characteristic, particularly hematocrit, of the blood 180-a' -sample containing the analyte, particularly glucose, and de riving a specific sampling time based on a relationship 160- T between the physical characteristic and sampling time so that the analyte concentration can be determined with greater ac 140- curacy with the specific sampling time point. 9Intervals= 1 2 3 4 56 7 8 9 11 0 80. 0 12 3 45 22 0 1 2 3 4 5 7 Time (s) Specific Range (or 2nd Sampling Ti Duration) T2 W O 2 0 13 /0 9 8 5 6 4 A 9 ||llll|||ll|||Dll llllllll l||||||||||||||||||||||||||||||||||||||||||||||||||||||||||I|||||| TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, (48) Date of publication of this corrected version: ML, MR, NE, SN, TD, TG). 31 October 2013 Published: (15) Information about Correction: - with international search report (Art. 21(3)) see Notice of 31 October 2013 - with information concerning authorization of rectifica tion of an obvious mistake under Rule 91.3 (b) (Rule 48.2(i)) WO 2013/098564 PCT/GB2012/053277 Accurate Analyte Measurements for Electrochemical Test Strip Based on Multiple Discrete Measurements Defined by Sensed Physical Characteristic(s) of the Sample Containing the Analyte [0001] This application claims the benefits of priority of prior filed US Provisional Patent Application Serial Nos. 61/581,087 (Attorney Docket No. DDI5220USPSP); 61/581,089 (Attorney Docket No. DDI5220USPSP1); 61/581,099 (Attorney Docket No. DDI5220USPSP2); and 61/58 1,100 (Attorney Docket No. DDI5221USPSP), all filed on the same day of December 29, 2011, and US Provisional Patent Application Serial No. 61/654,013 (Attorney Docket No. DDI5228USPSP), filed on 31st May 2012, and all the prior applications are hereby incorporated by reference as if fully set forth herein. [0002] Electrochemical glucose biosensors, such as those used in the OneTouch® Ultra® whole blood testing kit, which is available from LifeScan, Inc., are designed to measure the concentration of glucose in a blood sample from patients with diabetes. The measurement of glucose can be based on the selective oxidation of glucose by the enzyme glucose oxidase (GO). The reactions that can occur in a glucose biosensor are summarized below in Equations 1 and 2. Eq. 1 Glucose + GO(ox) - Gluconic Acid + GO(,,d) Eq. 2 GO(red) + 2 Fe(CN)3- - GO(ox) + 2 Fe(CN)6' [0003] As illustrated in Equation 1, glucose is oxidized to gluconic acid by the oxidized form of glucose oxidase (GO(ox)). It should be noted that GO(ox) may also be referred to as an "oxidized enzyme." During the reaction in Equation 1, the oxidized enzyme GOox) is converted to its reduced state, which is denoted as GOred) (i.e., "reduced enzyme"). Next, the reduced enzyme GO(red) is re-oxidized back to GOox) by reaction with Fe(CN)6 WO 2013/098564 PCT/GB2012/053277 (referred to as either the oxidized mediator or ferricyanide) as illustrated in Equation 2. During the re-generation of GOred) back to its oxidized state GO(ox), Fe(CN)63 - is reduced to Fe(CN)64 (referred to as either reduced mediator or ferrocyanide). [0004] When the reactions set forth above are conducted with a test signal applied between two electrodes, a test current can be created by the electrochemical re-oxidation of the reduced mediator at the electrode surface. Thus, since, in an ideal environment, the amount of ferrocyanide created during the chemical reaction described above is directly proportional to the amount of glucose in the sample positioned between the electrodes, the test current generated would be proportional to the glucose content of the sample. A mediator, such as ferricyanide, is a compound that accepts electrons from an enzyme such as glucose oxidase and then donates the electrons to an electrode. As the concentration of glucose in the sample increases, the amount of reduced mediator formed also increases; hence, there is a direct relationship between the test current, resulting from the re-oxidation of reduced mediator, and glucose concentration. In particular, the transfer of electrons across the electrical interface results in the flow of a test current (2 moles of electrons for every mole of glucose that is oxidized). The test current resulting from the introduction of glucose can, therefore, be referred to as a glucose current. [0005] Electrochemical biosensors may be adversely affected by the presence of certain blood components that may undesirably affect the measurement and lead to inaccuracies in the detected signal. This inaccuracy may result in an inaccurate glucose reading, leaving the patient unaware of a potentially dangerous blood sugar level, for example. As one example, the blood hematocrit level (i.e. the percentage of the amount of blood that is occupied by red blood cells) can erroneously affect a resulting analyte concentration measurement. [0006] Variations in a volume of red blood cells within blood can cause variations in glucose readings measured with disposable electrochemical biosensors. Typically, a negative bias (i.e., lower calculated analyte concentration) is observed at high hematocrit, while a positive bias (i.e., higher calculated analyte concentration) is observed at low hematocrit. At high hematocrit, for example, the red blood cells may impede the reaction of enzymes and electrochemical mediators, reduce the rate of chemistry dissolution since there is less plasma volume to solvate the chemical reactants, and slow diffusion of the WO 2013/098564 PCT/GB2012/053277 mediator. These factors can result in a lower than expected glucose reading as less current is produced during the electrochemical process. Conversely, at low hematocrit, fewer red blood cells may affect the electrochemical reaction than expected, and a higher measured current can result. In addition, the blood sample resistance is also hematocrit dependent, which can affect voltage and/or current measurements. [0007] Several strategies have been used to reduce or avoid hematocrit based variations on blood glucose. For example, biosensors have been designed to incorporate meshes to remove red blood cells from the samples, or have included various compounds or formulations designed to increase the viscosity of red blood cells and attenuate the effect of low hematocrit on concentration determinations. Other test strips have included lysis agents and systems configured to determine hemoglobin concentration in an attempt to correct for the effects of hematocrit. Further, biosensors have been configured to measure hematocrit by measuring an electrical response of the fluid sample via alternating current signals or change in optical variations after irradiating the blood sample with light, or measuring hematocrit based on a function of sample chamber fill time. A common technique of the strategies involving detection of hematocrit is to use the measured hematocrit value to correct or change the measured analyte concentration, which technique is generally shown and described in the following respective US Patent Application Publication Nos. 2010/0283488; 2010/0206749; 2009/0236237; 2010/0276303; 2010/0206749; 2009/0223834; 2008/0083618; 2004/0079652; 2010/0283488; 2010/0206749; 2009/0194432; or US Patent Nos., 7,972,861 and 7,258,769, all of which are incorporated by reference herein to this application. SUMMARY OF THE DISCLOSURE [0008] Applicant has provided various embodiments of a technique to allow for improved glucose measurement using a relationship between sampling time point and hematocrit to derive or calculate a specific sampling time point that can be used to calcula