Finger-Stick Glucose Monitoring

Since its introduction three decades ago, self-monitoring of blood glucose (SMBG) using finger-stick blood samples, test strips, and portable meters has aided diabetes management, principally by enabling patients—particularly those treated with insulin—to become full partners along with health professionals in striving for excellent glycemic control. Over time the use of glucose meters has become easier and faster with smaller and smaller blood samples yielding results in a matter of seconds. For this reason, glucose meters are now increasingly used in hospital wards, intensive care units, and other facilities such as dialysis units and infusion centers to provide point-of-care results that would take much longer through routine laboratory channels. This technology has largely taken the guess work out of diabetes management. Without such technology, intensive glucose control such as that achieved in the Diabetes Control and Complications Trial may not have been demonstrated to prevent or decrease microvascular complications; insulin pump therapy would not really be practical; and hypoglycemia would remain an even greater source of anxiety for patients and their families than it already is. We have come to rely so much on finger-stick glucose that it is easy to forget its limitations. In considering this we will discuss accuracy, specificity, and, in light of those, inappropriate usage. ### Accuracy Although there is no universally binding standard, guidelines issued by the International Organization for Standardization (ISO) are widely acknowledged. ISO guideline 15197 suggests that for glucose levels <75 mg/dl, a meter should read within 15 mg/dl of the reference sample, and for levels ≥75 mg/dl, the reading should be within 20%. A meter also should be able to meet these targets in at least 95% of the samples tested (1). Several examples serve to illustrate the implications of this degree of imprecision. Assuming a meter does indeed meet the ISO guideline, …