We hear a lot about meter accuracy on the forum with some people testing with more than one meter and being surprised that the two readings are not even close.
This article is worth reading as to why meters cannot tell us our blood sugar levels.
I thought it was interesting and was surprised to see that Tyenol, (paracetemol) could make a difference to a reading.
Home vs. Hospital Testing
Most home meters measure glucose in so-called “whole blood” (blood as it comes out of our body). Whole blood consists of a liquid, called plasma, and cells, mainly red cells. The percentage of red cells is called the hematocrit. The standard reference lab test measures glucose in plasma (about half to two thirds of the volume of blood).
Home meters are calibrated to give results as though they are measuring glucose in plasma only (called “plasma-equivalent” results). That said, to some degree we’re already on two different playing fields. Second, laboratory tests eliminate virtually all variation, except for manufacturing variation, from their testing.
Some factors have to do with the meter, some with the strip and some, with us PWDs.
In fact, the biggest contributor to inaccuracy is the strips. Here’s the process as simply as I can put it: glucose interacts with an enzyme on the strip, releasing electrons. Another agent on the strip, called the “mediator,” turns these electrons into an electrical current. The greater the glucose concentration, the greater the current. That current then speeds through the strip. Finally, an algorithm (formula) in the meter converts the current into a concentration of glucose. And voila! You get a number.
But there’s a long list of factors that affect meter/strip accuracy:
http://www.diabetesmine.com/2012/09/why-meters-cant-tell-us-our-blood-sugar-levels.html
This article is worth reading as to why meters cannot tell us our blood sugar levels.
I thought it was interesting and was surprised to see that Tyenol, (paracetemol) could make a difference to a reading.
Home vs. Hospital Testing
Most home meters measure glucose in so-called “whole blood” (blood as it comes out of our body). Whole blood consists of a liquid, called plasma, and cells, mainly red cells. The percentage of red cells is called the hematocrit. The standard reference lab test measures glucose in plasma (about half to two thirds of the volume of blood).
Home meters are calibrated to give results as though they are measuring glucose in plasma only (called “plasma-equivalent” results). That said, to some degree we’re already on two different playing fields. Second, laboratory tests eliminate virtually all variation, except for manufacturing variation, from their testing.
Some factors have to do with the meter, some with the strip and some, with us PWDs.
In fact, the biggest contributor to inaccuracy is the strips. Here’s the process as simply as I can put it: glucose interacts with an enzyme on the strip, releasing electrons. Another agent on the strip, called the “mediator,” turns these electrons into an electrical current. The greater the glucose concentration, the greater the current. That current then speeds through the strip. Finally, an algorithm (formula) in the meter converts the current into a concentration of glucose. And voila! You get a number.
But there’s a long list of factors that affect meter/strip accuracy:
- Meter calibration, coding, enzymes and mathematical algorithms (all different in different meters)
- Variable enzymes in strips
- Mediator oxidation and strip freshness/age
- Strips differ somewhat, lot to lot, with somewhat different precision ranges for each lot
- Strips differ in well size (the space in a strip that holds the blood)
- Interfering substances in one’s blood from medications (something as simple as Tylenol), and every manufacturer’s nightmare, hematocrit — that percentage of red blood cells in blood, which can interfere with the electrical current
- Environmental conditions: temperature, climate, altitude
- Lack of meter maintenance
- User error – forgetting to code the meter or coding it incorrectly; not washing hands before testing (there may be some sugar residue on your fingers or sweat on hands); leaving strips exposed to air too long; or using expired strips
http://www.diabetesmine.com/2012/09/why-meters-cant-tell-us-our-blood-sugar-levels.html
