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Question:

From Memphis, Tennessee, USA:

We have tried using a continuous glucose sensor with my son. It normally hits within 10 to 20 points of his blood sugar measured with a standard glucose meter, but the two numbers are rarely the same. If he has a sensitivity factor of 1:200, would it be safe to base his bolus on the sensor number? Also, I know that regular glucose monitors have a certain percentage of errors; how do current glucose sensors compare?

Answer:

This is a good question!

The upcoming generation of glucose sensors should be more accurate and give more "real time" readings.

The CGMS® System Gold manufactured by Medtronic/MiniMed is also good but not made for home use. It has some limitations on the low end of glucose ranges.

REMEMBER: The glucose sensors are measuring the glucose in the "interstitial fluid," i.e., the fluid that is between cells throughout the tissues. It is VERY similar in its chemical makeup to blood serum, but is not exactly the same. The correlation with glucose is more than 90% (but it is not 100%). This could account for some discrepant readings between the sensor and the glucose meter.

As you alluded, the glucose monitors also have some imperfections. By and large, they are within 10 to 20% (or less) of the actual serum glucose. That is, if the serum glucose is ACTUALLY 100 mg/dL [5.6 mmol/L], the glucose meter may give a value ranging from 80 to 120 mg/dl [4.4 to 6.7 mmol/L]. (This is why we don't use these meters for DIAGNOSING diabetes.) There can be some concerns when the glucose value reads low, but symptoms of hypoglycemia can reinforce matters. When the glucose is actually high, for example, 300 mg/dL [16.7 mmol/L], if the reading given is 240 to 360 mg/dl [13.3 to 20 mmol/L], the fact of the matter is, the glucose is still too high.

So, this can also contribute to discrepant sensor and meter readings. Clearly, the sensor technology is not perfect (nor is glucose meter technology), but I would want the values less than 50 points different when making a CLINICAL decision. Personally, if the value were more than 50 points different, I would give insulin based on your "ol' reliable glucometer."

DS

DTQ-20060927103224
Original posting 3 Oct 2006
Posted to Blood Tests and Insulin Injections and Research: Monitoring

  
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Last Updated: Tuesday April 06, 2010 15:10:10
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