Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED GLUCOSE MONITOR AND TEST ST~IP
CONTAINERS FOR USE IN SAME
DESCRIPTION
BA~KGROUND OF T~E INVENTION
This application relates to an improved type of
glucose monitor which is automatically calibrated for the
particular test strips being used, and to test strip
containers for use in such a monitor.
~ lucose monitoring is a fact o~ everyday li~e
~or diabetic individuals, and the accuracy o~ such
monitoring can literally mean the difference between life
and death. To accommodate a normal li~e style to the
need for ~requent monitoring o~ glucose levels, a number
o~ glucose meters are now available which permit the
individual to test the glucose level in a small amount o~
~lood. The success o~ these devices, however, depends on
the ability of the user to obtain a correct reading.
Many o~ the meter designs currently available
make use o~ a disposable test strip which in combination
with the meter measures the amount o~ glucose in the
blood sample electrochemically. Lot-to-lot variation
during the manufacture o~ test strips requires that the
user calibrate the system for each batch o~ strips. This
is normally accomplished by inserting a calibration
strip, provided with each package of test strips, into
the meter. This process introduces the possibility o~
error as a result of ~ailure of the user to per~orm the
calibration procedures in the correct manner or at the
correct times. In particular, errors in calibration can
occur if a user opens a new package o~ test strips and
fails to perform the calibration step or if a user has
several packages of test strips open and confuses the
calibration strips between the packages.
It is an object of the present invention to
provide a meter, and particularly a glucose meter, which
obviates the need for user initiated calibration.
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It is a further object of the invention to
provide a meter, and particularly a glucose meter, which
~ ~ reduces the likelihood of a test strip being used with
the incorrect meter calibration.
5UMM~ F THE INV~TION
These and other objects of the invention are
provided by a test meter of the type which receives a
disposable test strip and a sample of bodily fluid from a
patient and performs an electrochemical analysis of the
amount of an analyte, for example glucose, in the sample
that includes a receptacle for receiving a container in
which disposable test strips are provided, and a mechan-
ism ~or reading calibration values calibration values
specific to the disposable test strips that are a~ixed
to the container. For example, calibration values can be
applied to the container in the form of a machine
readable bar-code, a magnetic stripe, a memory chip or as
a resonant wire loop. By automatically obt~i n; ng
calibration values from the container in which the strips
are provided, the chances of using the wrong calibration
information are greatly reduced.
In addition to calibration values, the
container may contain additional information readable by
the meter which will enhance the safety of the individual
using the device. For example, the container may include
a machine readable expiration date, which would permit
the meter to either give a warning or to refuse to
process a test strip which was beyond its expiration
date. In addition, the container may include information
about the number of test strips in the container. Since
any effort to process more strips than were originally
supplied in the container would in all likelihood result
in the use of the wrong calibration codes, a warning or
re~usal to process the strip would be appropriate in this
instance as well
_
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BRT~ DES~RIPTION OF THE D~AWTNGS
Fig. 1 shows a cross ~ection of a glucose meter
~ ~ in accordance with the invention;
Fig. 2 shows a top view of a glucose meter in
accordance with the invention;
Fig. 3 shows one embodiment of a receptacle for
receiving a container of test strips in accordance with
the invention;
Fiy. 4 shows one embodiment of a receptacle for
receiving a container of test strips in accordance with
the invention;
Fig. 5 shows the functional parts of a meter in
accordance with the invention schematically;
Figs 6A - 6B illustrate the operation of
several embodiments of the inventions; and
Fig. 7 shows a container in accordance with the
invention.
DETAILED DESCRIPTION OF THE INVENTION
Figs. 1 and 2 shows a meter in accordance with
the invention. The meter has a top housing member 1 and
a bottom housing member 2. Bottom housing member 2 has a
receptacle 7 affixed thereto for receiving a container 10
of test strips. Bottom housing member 2 also has an
opening for receiving batteries to power the meter which
is sealed in use by battery cover 4. Top housing member
1 has openings formed therein for a liquid crystal or
light emitting diode display 3, and for control buttons
5. In addition, top housing member 1 and bottom housing
member 2 taken together form a slot 12 into which a test
strip is inserted for measurement of glucose.
Fig. 3 shows a detailed view of one embodiment
of a receptacle for a test strip container in accordance
with the present invention. The receptacle 7 is open at
the front end 31 to receive a test strip container and
has a retractable catch 32 for holding the container in
position in the receptacle. On one surface of the
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xeceptacle 7 is an opening 33 through which machine-
readable character~, e.~. a bar code, printed on the
~ ~ container can be read. Although the receptacle 7 in Fig.
3 is shown as a regular shape, it may be desirable to
make the container and the receptacle of corresponding
asymmetrical shapes to ensure alignment of the machine-
readable characters with the opening.
Fig. 4 shows a cross section of an alternative
embodiment of the receptacle 7, In this embodiment, a
line of electrical contacts 41 are arranged to engage
with a corresponding set of contacts on the container to
that information stored on a chip built into the
container can be made. The contacts 41 are in turn
connected to the meter for processing of the information.
Fig. S shows a functional parts of the glucose
meter of the invention schematically for purposes of
understanding the operation of the invention. As shown,
coded information 50 recorded on a test strip container
10 disposed within receptacle 7 is functionally connected
to means 51 for reading the information affixed to the
container. The means for reading the information must, of
course, be compatible with the manner in which the
information 50 is recorded on the container. Thus, for
example, in the case of information recorded in a bar-
code ~ormat, the means 51 ~or reading the in~ormationaffixed to the container will be a bar-code reader. For
a magnetic strip, the means 51 will be a magnetic stripe
reader. In the case where the information on the
container is recorded in a memory chip, for example a
"TOUCH MEMORY" chip manufactured by Dallas Semiconductor
or other semiconductor device capable of storing
information for retrieval by a remote device, the means
51 for reading the information is a microprocessor which
sends a ~uery to the chip and receives back a signal
reflecting the stored contents of the chip. In the case
where the information is stored as a resonating wire
loop, the resonating frequency of which indicates the
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information, the means 51 for reading the information is
an rf generator and detector which scans across possible
~ ~ resonance frequencies and monitors for a resonant
emission ~rom the wire loop.
The means 51 for reading the information is
functionally connected to a microprocessor 52 for con-
trolling the device. When the user depresses the start
key 5, the microprocessor 52 queries the means 51 for
reading the information ~rom the container and either
evaluates the sample which has placed in the slot 12,
evaluates the sample with a warning to the user, or
refuses to evaluate the sample. If the sample is evalu-
ated, with or without a warning, the microprocessor
receives output from the electrodes 53 on the test strip,
applies the calibration factors received from the means
51 for reading the in~ormation from the container, and
causes the resulting glucose level to be displayed on
display 3.
Figs. 6 A - E illustrate several variations of
information 50 which can be recorded on a container in
accordance with the present invention, and the ways in
which the microprocessor 52 can make use of the recorded
in~ormation. In Fig. 6A, the information 50 recorded on
the container is simply the calibration values for the
test strips in the container. In this case, the
microprocessor 52 simply applies the calibration values
to the raw electrode output and converts it to a digital
value, to arrive at a calibrated glucose display.
In Fig. 6B, the information 50 recorded on the
container includes both the calibration values and the
number of test strips originally in the container.
Microprocessor 52 maintains a register 60 in which a
counter X is stored. The counter X is set to zero
whenever a new container is loaded into the receptacle 7,
~ 35 and is incremented each time a test strip is evaluated.
Each time the meter is used, the microprocessor 52
compares the value of X stored in register 60 to the
,
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number of test strips originally in the container. If the
X is less than or equal to the original number o~ test
~ ~ strips, the microprocessor operates in a normal m~nner
and a calibrated glucose value is displayed. If X is
greater than the original number o~ strips, the
microprocessor generates an error signal. This error
signal may cause the meter to provide a result together
with a warning that the result is suspect, or may cause
the microprocessor to refuse to display a result at all.
Fig. 6C shows an em~odiment in which the
information 50 recorded on the cont~ ner includes cali-
bration values and an expiration or manufacturing date.
In this case, the microprocessor 52 includes a clock 61
which is set initially by the user or by the factory and
which is incremented automatically by the microprocessor
to maintain the date accurately. The microprocessor 52
compares the expiration date recorded on the container to
the clock, and acts in one o~ three ways depending on the
results o~ this comparison. As shown, when the actual
date is be~ore the expiration date by some pre-determined
threshold amount, ~or example 10 days, the microprocessor
~2 simply generates a calibrated glucose display. When
the actual date is closer to the expiration date than the
predetermined threshold, and perhaps ~or several days
after the expiration date, the microprocessor 52
generates a low level error signal which causes the meter
to display a calibrated glucose reading along with a
warning. Thereafter, the microprocessor generates a high
level error signal which results in the meter re~using to
provide a reading.
A variation on the embodiment shown in Fig. 6C
would use the clock to also monitor the time since the
container was placed in the receptacle. In this case, as
shown in Fig. 6D, the microprocessor would also include a
storage register 64 in which the date on which a new
container is placed in the receptacle is stored. In
addition to checking the expiration date, the
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microprocessor 52 would also compare the current date to
the date stored in register 62 If this difference were
~ ~ greater than a predetermined threshold level, the meter
would generate a warning and/or refuse to operate. This
embodiment is particularly useful where the shelf life of
the test strips in the sealed container is longer than
the shelf li~e after the cont~iner has been opened for
first use. In addition, by generating a warning when a
container of strips is lasting longer than expected, the
1~ meter could provide a rPmin~r that tests need to be
performed on a regular basis.
Fig. 6E shows a further embodiment of the
invention in which the information 5~ stored on the con-
tainer includes both calibration values and the identifi-
cation of the analyte for which the strip is intended.This embodiment is particularly useful where disposable
test strips for several analytes, ~or example gluco~e and
ketones can be evaluated in the same meter but require
different processing of the raw data to obtain optimum
results.
T~e various types of information and the
resulting processing options depicted in the Figs 6A-6E
can be used in any combination. Thus, for example, a
container in accordance with the invention might include
calibration values, analyte ID and expiration date;
calibration values, number of strips and expiration date;
number of strips and expiration date; or any other
combination of information types.
While the checks described above will greatly
reduce the chances of using incorrect calibration values
or out-of-date test strips, it may also be advantageous
to provide the ability to deactivate the information
stored on the container so that it cannot be used beyond
a certain point. For example, deactivation of the
container after a number of tests had been run equal to
the number of strips into the container would eliminate
the possi~ility that an individual might place additional
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test strips which did not match the calibration values of
the container.
~ ~ The mechanism of deactivation, like the
mechanism for reading the information depends on the
manner in which the in~ormation is stored. For example,
in the case of a bar-code, the information might be
rendered unreadable by exposing a photosensitive region
to light which causes a color chanye for example to alter
the bar code to an unreadable pattern. For an emitter
loop, a ~usible link can be included which is fused by a
pulse of an appropriate fre~uency, render the shorting
the emitter loop and rendering it inoperative. In the
case of a proy.d.ll..dble memory chip, deactivation might be
accomplished by writing over a portion of the stored
information, or by inducing a magnetic field near the
chip of suf~icient magnitude to render the stored
information meaningless, and there~ore unreadable. The
generation of a magnetic ~ield will also render a
magnetic stripe inoperative.
A ~urther aspect of the present invention is
the containers which can be used in the meter according
to the invention. As shown in Fig 7, such a container
generally comprises a sealable body member 70 for
receiving at least one glucose test strip; and machine-
readable means 71 for storing information specific to
disposable test strips provided in the container. As
will be apparent ~rom the foregoiny discussion o~ the
alternative reading means which can be included in a
meter according to the invention, the machine readable
means 71 can be a bar-code, a memory chip, or a resonant
wire loop, or any other ~orm o~ machine readable storage
which can be adapted ~or use in a small device o~ the
type claimed.