Glucose meter accuracy criteria as defined in ISO 15197 (1) and CLSI guidelines require that for glucose values above 75 mg/dL, 95% of glucose meter results be within 20% of the reference glucose value. There has been growing momentum towards revision of these guidelines, primarily because of the changing paradigm of glycemic control in the hospital. These glycemic control protocols may require greater accuracy of glucose monitors in order to avoid severe hypoglycemia (SH) in patients receiving intravenous insulin. Even one episode of SH (glucose concentration < 40 mg/dL) is associated with an increased risk for death in the ICU and hospital. The observation that the most dramatic positive outcomes from well-performed trials of glycemic control were obtained in studies that used more accurate blood gas analyzers to measure glucose levels (2); while follow-up studies that relied upon less accurate handheld glucose meters resulted in neutral or negative findings (3,4,); has fueled interest in the issue of what level of glucose monitor accuracy is required for safe and effective glycemic control in the hospital. The FDA has taken an interest in the question, holding a public forum in March 2010 to solicit input from the general public and healthcare experts on what level of accuracy should be required for hospital-use glucose meters.
It now seems likely that the FDA will tighten accuracy requirements for hospital use glucose meters, though the level of accuracy that will be required is not yet known. An error simulation model study suggested that glucose meters than maintain a 15% (as opposed to 20%) total error tolerance will prevent large insulin dose errors even with tight glycemic control protocols (5). However other experts suggest that a 5% or 10% error tolerance limit might be required to safely manage hospital patients on glycemic control protocols. In the midst of these debates many facilities have moved towards more moderate glycemic control protocols, which presumably will not demand as much glucose monitor accuracy as the original tight glycemic control protocols.
Within three ICUs in our institution we have recently measured rates of severe (< 40 mg/dL) and moderate (40-60 mg/dL) hypoglycemia for one month, both before and after modifying our glycemic control protocol from a more traditional tight glycemic control (target 80-130 md/dL) to a more moderate (target 110-150 mg/dL) glycemic control protocol. Rates of severe hypoglycemia went from 1.4 to 0%; while rates of moderate hypoglycemia went from 7.7 to 0.5% by changing the glycemic target. Causes of SH episodes were investigated during the tight glycemic control era, and 90% were found to be due to protocol violations (glucose reading not taken, glucose reading not acted upon appropriately). Glucose meters that at best met current ISO 15197 criteria were used for all glucose monitoring. This is not to say that glucose monitor accuracy is not important, only that other factors (glucose target range, protocols and systems in place to insure protocol compliance) may be relatively more important than glucose monitor accuracy in avoiding hypoglycemia in the ICU. Based upon available evidence and experience, I believe that bedside glucose meters that maintain a 15% total error criteria will be safe and effective for hospital use. Do you agree or disagree? What do you feel should be required of glucose monitors for use in the ICU or for glycemic control protocols?