Re: [IPk] Continuous Glucose Monitoring
I've been to several presentations about both the Guardian RT and other
continuous monitoring systems currently being developed. One of the things
that we *must* remember is that only earlobes, fingertips and toes provide
us with convenient capillary blood glucose measurements. Subcutaneous
sensors usually rely on interstitial fluid. In general you won't find the
same amount of glucose in the capillary blood and the interstitial fluid at
the same time. The margin of difference between the two readings is an
indication of how close or far apart chronologically the measurements are.
It takes time for blood to flow through all tissues of the body. Just
because your fingerstick and your Guardian RT are not correlating at the
time of measurement does not mean that the curves would not be
superimposable though c.15 mins 'apart' if you did a venous or fingerstick
bg every time the Guardian RT took a reading.
We have gotten so convinced that fingerstick bgs are the ultimate measure of
accuracy but they're not. First, they are about 11 minutes 'off' from venous
bgs; second, a fingerstick bg is +/-10% compared to a laboratory test. And
it's the frequency of self/home bg monitoring that makes the numbers useful
and helps us detect patterns and causes and effects, NOT their relationship
to laboratory values per se.
The argument about whether continuous monitoring is accurate is getting
almost as annoying to me as the argument over whether Shakespeare was
anti-Semitic. Most continuous monitors (A) that have been developed do
accurately measure interstitial fluid (B). Sadly, interstitial fluid (B)
does not mirror capillary blood glucose (C). So: A yields B, but B does not
yield C because A is not equal to C.
Type 1 11+ years; MiniMed pumper 7.5 years; Animas pumper 1 year
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