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System and methods for processing analyte sensor data

System and methods for processing analyte sensor data description/claims

This application is a divisional of Ser. No. 11/038,340 filed Jan. 18, 2005, which is a continuation of Ser. No. 10/632,537, filed Aug. 1, 2003. The disclosures of each of the above-mentioned applications is hereby expressly incorporated by reference in its entirety and is hereby expressly made a portion of this application.

The present invention relates generally to systems and methods for analyte sensor data processing. Particularly, the present invention relates to retrospectively and/or prospectively initiating a calibration, converting sensor data, updating the calibration, evaluating received reference and sensor data, and evaluating the calibration for the analyte sensor.

Diabetes mellitus is a disorder in which the pancreas cannot create sufficient insulin (Type I or insulin dependent) and/or in which insulin is not effective (Type 2 or non-insulin dependent). In the diabetic state, the victim suffers from high blood sugar, which may cause an array of physiological derangements (e.g., kidney failure, skin ulcers, or bleeding into the vitreous of the eye) associated with the deterioration of small blood vessels. A hypoglycemic reaction (low blood sugar) may be induced by an inadvertent overdose of insulin, or after a normal dose of insulin or glucose-lowering agent accompanied by extraordinary exercise or insufficient food intake.

Conventionally, a diabetic person carries a self-monitoring blood glucose (SMBG) monitor, which typically comprises uncomfortable finger pricking methods. Due to the lack of comfort and convenience, a diabetic will normally only measure his or her glucose level two to four times per day. Unfortunately, these time intervals are so far spread apart that the diabetic will likely find out too late, sometimes incurring dangerous side effects, of a hyper- or hypo-glycemic condition. In fact, it is not only unlikely that a diabetic will take a timely SMBG value, but the diabetic will not know if their blood glucose value is going up (higher) or down (lower) based on conventional methods, inhibiting their ability to make educated insulin therapy decisions.

Systems and methods are needed that accurately provide estimated glucose measurements to a diabetic patient continuously and/or in real time so that they may proactively care for their condition to safely avoid hyper- and hypo-glycemic conditions. Real time and retrospective estimated glucose measurements require reliable data processing in order to provide accurate and useful output to a patient and/or doctor.

Similarly, systems and methods are needed that accurately provide substantially continuous estimated analyte measurements for a variety of known analytes (e.g., oxygen, salts, protein, and vitamins) to provide prospective and/or retrospective data analysis and output to a user.

Accordingly, systems and methods are provided for retrospectively and/or prospectively calibrating a sensor, initializing a sensor, converting sensor data into calibrated data, updating and maintaining a calibration over time, evaluating received reference and sensor data for clinical acceptability, and evaluating the calibration statistical acceptability, to ensure accurate and safe data output to a patient and/or doctor.

In a first embodiment a method is provided for initializing a substantially continuous analyte sensor, the method including: receiving a data stream from an analyte sensor, including one or more sensor data points; receiving reference data from a reference analyte monitor, including two or more reference data points; providing at least two matched data pairs by matching reference analyte data to substantially time corresponding sensor data; forming a calibration set including the at least two matching data pairs; and determining a stability of the continuous analyte sensor.

In an aspect of the first embodiment, the step of determining the stability of the substantially continuous analyte sensor includes waiting a predetermined time period between about one minute and about six weeks.

In an aspect of the first embodiment, the step of determining the stability of the substantially continuous analyte sensor includes evaluating at least two matched data pairs.

In an aspect of the first embodiment, the step of determining the stability of the substantially continuous analyte sensor includes evaluating one of pH, oxygen, hypochlorite, interfering species, correlation of matched pairs, R-value, baseline drift, baseline offset, and amplitude.

In an aspect of the first embodiment, the method further includes providing one of an audible, visual, or tactile output to a user based on the stability of the sensor.

In an aspect of the first embodiment, the step of providing output based on the stability of the sensor includes indicating at least one of a numeric estimated analyte value, a directional trend of analyte concentration, and a graphical representation of an estimated analyte value.

In an aspect of the first embodiment, the step of receiving sensor data includes receiving sensor data from a substantially continuous glucose sensor.

In an aspect of the first embodiment, the step of receiving sensor data includes receiving sensor data from an implantable glucose sensor.

In an aspect of the first embodiment, the step of receiving sensor data includes receiving sensor data from subcutaneously implantable glucose sensor.

In an aspect of the first embodiment, the step of receiving reference data includes receiving reference data from a self-monitoring blood glucose test.

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