From Pennsylvania, USA:
To get more accurate blood sugar readings, should we use a meter which is plasma-calibrated or whole blood calibrated? Articles that we have read indicate that plasma-calibrated meters have readings which are about 12 percent higher? Why do they make two different types?
That is a great question, one that will soon be moot since most of the meters are going to the plasma reference. It is not a case of making two kinds of meters, but rather a case of how the test strips are being read.
In the early 1980s when blood glucose monitors for patients first appeared, it was established that they should read the glucose as a whole blood glucose test would read, since they were a whole blood glucose test. As I understand it, in Europe they decided to calibrate the meter so that the numbers would be equivalent to a plasma reading (about 10-15% higher than whole blood). This required the companies to have meters reading strips two ways and increased the complexity for the meter companies.
In the last year or two all of the meter companies seem to be switching to plasma referenced meters and strips and, as of right now, there are only a few of them left that read whole blood. It isn't a matter of which is more accurate; it is how you like to look at the number. The meter can be perfectly accurate or inaccurate reading either way. It's kind of like my bathroom scales at home: I know that they are about 7 pounds light but I prefer to think that the doctor's scales are reading heavy! If you are using a meter that is plasma referenced, you are looking at the blood glucose the same way the lab analyzer looks at it. If you can get your pre-meal blood glucose into the 80-120 mg/dl range on a plasma referenced meter, you will see a HbA1c in the excellent range.
What you really should do is find the meter that fits your lifestyle and preferences for size, speed and cost and make sure it is accurate by doing a control test and maybe doing a test at the doctors office at the same time they send a glucose to the lab for comparison.
It can be very confusing trying to use two different meters that are calibrated to two different standards. If you have several meters, make sure they are all referenced the same way. I'm pretty sure that all the new sensor-type meters are plasma referenced at this time. If you aren't sure which kind of meter you have, call the 800 number for the meter company and they can tell you how their meter and strips are calibrated.
Original posting 21 Mar 1999
Posted to Blood Tests and Insulin Injections
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