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Re: [IP] Re: testing with uncalibrated strips!
<< >I realized this morning I have been testing at least one or two vials
>of strips without realizing the code numbers didn't match the meter's.
>When I called Lifescan (I use the Ultra) to try to determine how far
>readings were, the rep said there was no way to know, but that they
>indeed incorrect. >>
OK, I generally write the meter column for Diabetes Interview. Sorry I can't
access the final version, but here's the raw copy for the column that ran in
Knitters know that, for a perfect match, you need to buy all the yarn for a
project from the same dye lot to eliminate subtle changes in color that can
make your solid red sweater come out looking like it has stripes. The reason?
Minute changes in dyes that cause just the slightest difference in hues of
the same color.
It's a similar scenario with the strips you put in your meters to test
your blood glucose: Minute changes in batches of the chemicals that make up
the reagents in the strips can cause fluctuations in readings.
Unlike slightly mismatched yarns, however, mismatched codes between strips
and meters can cause you to err in correcting your blood glucose. To avoid
getting an error in your blood-glucose readings, you need to calibrate your
meter so that it matches the code-or number-stamped on the strip container.
"All blood-glucose metersb&use whole blood, which is applied directly to
the reagent," says Edie A. Elkinson of the Chico Chandler Agency in New York
City, which represents Ascensia. "The reagent itself measures the amount of
glucose dissolved in the plasma portion of the whole blood. The red cells are
left on top of the reagent and the liquid plasma with dissolved glucose
diffuses into the reagent to be measured."
The reagent is comprised of a mixture of raw ingredients that vary from
batch to batch. As Elkinson explains, "There is a certain amount of
manufacturing variability due to raw materials, manufacturing lines and
environmental conditions. It is very difficult or nearly impossible to
reproduce the same reagent batches time and time again."
It's that variance that calls for coding your meter each time you open a
new box or vial of strips. Some meters include chips to insert, others
require you to reset numbers on the meter to conform with the code and
some-including Roche's Compact meter, which has a bar code on the drum of
strips-calibrates the meter for you.
When you insert the chip that "tells" the meter what the code is, or
manually change the numbers on the meter to change the code, "the calibration
code assigned to a lot of test strips provides an internal adjustment to the
meter glucose reading algorithm," says Holly Kulp. "This means the strip and
meter will perform together as a highly accurate system." Kulp is vice
president of professional relations and customer service for TheraSense of
How do companies determine the accuracy of each batch of reagents? They
test them, using control solutions and, in some cases, whole blood.
Roche is one company that tests the solutions using whole blood, in
addition to using control solutions, says Nancy Lonsinger, director of
consumer marketing for Roche Diagnostics in Indianapolis, Indiana.
No, Roche does not go to the blood bank to make a withdrawal: It pays people
to stick their fingers and contribute a drop of blood. Being paid to test?
What a job!
Batch-by-batch testing, using both control solutions and whole blood "is
the best method to correct for small variations rather than a range of
performance," Lonsinger says. "We uniquely set codes for each lot [and] each
set of strips is set for a unique code."
Elkinson says, "studies have shown that most users do not code their
meters properly or are not aware that this should be done."
This was borne out by a recent discussion on a diabetes mail list where
some members believed the code numbers on the strip containers were not
calibration codes but, rather, indicated the age of the strips: The lower the
number, the older the strips. Nope. Expiration dates are clearly printed on
the outside of the box the strips are sold in, as well as on the individual
While all of the representatives contacted say errors are generally small
if the meter is not calibrated to the strip reagent lot, all agree that it is
important to recode meters that need to have the codes set.
"There is a potential that readings on the meter may be less accurate,"
Lonsinger says, adding that while result errors may be minimal in most cases,
"on rare occasions [errors in readings] may be significant."
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