Hospitals employ a variety of POC glucose meters to quickly detect hypoglycemia and hyperglycemia among hospitalized patients and meet the blood glucose goals of the patient. But despite the ease of use, not all POC glucose meters exhibit comparable performance characteristics among the general patient population and the critically ill patient population. Yesterday’s morning short course, “The Accuracy of Point-of-Care Glucose Testing and Its Impact on the Management of Critically Ill Patients,” was timely. The moderator opened the interactive session by polling the audience on various questions that included: What types of glucose meters are used in your institution? How did you validate or plan to validate the accuracy of glucose meters? How do you define critically ill patients? and What are your policies that govern glucose meter use in critically ill patients?
The first presenter, Yusheng Zhu, PhD, DABCC, recipient of the 2015 Critical and Point-of-Care Testing Research Grant, discussed the accuracy and limitations of several POC glucose meters and the relevant enzymatic principles—glucose oxidase, glucose dehydrogenase, and hexokinase reactions. Zhu pointed out the importance of having trained healthcare professionals to operate the meters with the ability to identify factors such as faulty device connectivity and inappropriate temperature/humidity conditions that can lead to erroneous resutls.
Zhu highlighted the current Clinical and Laboratory Standards Institute (CLSI) requirements for glucose meter accuracy: 95% of glucose results obtained via the POC glucose meter must agree within +/- 12 mg/dL of glucose results obtained via the reference laboratory method results at glucose concentrations <100 mg/dL, and within +/- 12.5% via the reference laboratory method results at glucose concentrations ≥100 mg/dL. In contrast, the recently published FDA draft guidance for new POC glucose meter proposes that 99% of the POC glucose values must be within +/- 10% of the reference laboratory method results at glucose concentrations ≥ 70 mg/dL, and within +/- 7 mg/dL at glucose concentrations <70 mg/dL.
The second presenter, Kathie L. Hermayer, MD, a diabetologist, began her presentation stating that “the lab is my best friend and I could not do what I do without them.” She explained the distinct pathophysiology of critically ill patients compared to the general patient population. She discussed how to effectively define critically ill patients, why this must be performed by each institution, and the specific interferences and limitations of currently available glucose meters when used for these patients.
Specifically, critically ill patients have a higher incidence of anasarca, blood gas derangements, dehydration, diabetic ketoacidosis, hypotension, hypothermia, nonketotic hyperosmolar conditions, polycythemia, severe anemia, and polypharmacy–any of which may negatively interfere with the accurate measurement of glucose via a POC meter. She shared her own institution’s experience in which a committee comprised of the clinical laboratory team, critical care committee, and diabetic care specialists identified four major conditions in which glucose testing via POC meters was contraindicated: anasarca (extreme generalized edema), hypotension, hypothermia, and vasopressor usage (phenylephrine, vasopressin, and norepinephrine).
She ended the session by critically reviewing the new FDA guidelines and discussing the quality requirement for future POC glucose meters that could be used for critically ill patients from a clinician’s perspective.