Glucose meter accuracy is of paramount importance to every glucose meter user because of the implications of false readings. False high or low readings can precipitate a series of events that can have catastrophic consequences, especially if a false reading causes a person to adjust an insulin injection that is insufficient or in an overdose amount. Accuracy is not only the concern of users, but of the manufacturers of glucose meters. Inaccurate meters will most definitely setup a manufacturer for a suit if the meter is a significant element in a catastrophic event resulting from reliance on a glucose meter. All legitimate glucose meter manufacturers painstakingly test their meters to assure quality and compliance to Federally established standards.
In order to assure reliable quality, the U.S. Federal Drug Administration requires that all glucose meters comply with the International Standards Organization (ISO) standards for glucose meters. ISO 15197 requires that glucose meters consistently estimate glucose concentration within 20% of the more accurate laboratory analysis of glucose concentrations. It requires that this standard is met for 95% of all tests, if the test is on concentrations of glucose at 75 mg/dl. This means that a meter reading of 100 mg/dl can be either 120 or 80 mg/dl and be in compliance. It also means that if, out of every hundred readings, 5 of those readings that might have been 100 under laboratory conditions, could be 200 by the meter’s estimation and yet that meter would be in compliance. It is obvious that glucose meter accuracy under these standards may sometimes be highly inaccurate and yet in compliance with industry standards.
For those who cannot tolerate this variance, an easy way to check accuracy is to test your blood glucose levels with two different meters at about the same time. Using two meters manufactured by different companies increases the probability that significant differences will be revealed. Of course, if these two differ widely, you now have the additional problem of determining which one is inaccurate. A third meter for a third test would likely resolve this problem. Generally, meters exceed standards, so you should not be too concerned.
Glucose meter accuracy is more fundamentally challenged by factors other than the meter’s reliability. The test strips, which meters rely on to generate a pulse of electricity from the interaction of blood and the chemicals on the strip, the strength of which determines the level of glucose found in the drop of blood. The test strip may be dirty, cracked, aged, or have counteracting substances added to it when it was handled. This can interfere with the expected chemical reactions. Ambient temperature can also impact the reading. If the blood sample is too small or, for any number of reasons, not representative of the body’s blood, then the glucose meter accuracy will be off. What the blood contains may also skew the readings. For the user, this means that they should have clean hands when handling strips, that the strips should be handled by their edges, that the area to be tested is clean and wiped, that the lancets should be clean, that a consistent room temperature should be in effect, and that a sufficient amount of blood is taken.
Even with these challenges, glucose meter accuracy is fairly stable and reliable. If sudden extreme readings occur, the user should be cautious about what steps to take next. Those with hypoglycemia should be particularly careful. If the reading is dangerously high or low, and if you can make it to a hospital, go! In most cases you can depend on glucose meter accuracy, but before taking extreme action, if time permits, get a second opinion, even if it’s only another meter’s reading.