Alternative site blood glucose testing: a multicenter study

The aim of this study was to compare glucose measurements between fingertip and forearm using the blood glucose (BG) monitoring system One Touch Ultra (LifeScan), an electrochemical sensor that requires only a very small drop of blood (1 microL). Patients with type 1 or type 2 diabetes were identified in five outpatient diabetes clinics. Participants were requested to use the One Touch Ultra at home for 1 week for the measurement of BG levels from both sites. Patients filled in a questionnaire about their experience with testing blood samples from fingertip and forearm. The agreement between the measurements from the two sites was assessed using linear regression analysis, mean absolute relative error (MARE), the Bland-Altman method, and Error Grid Analysis (EGA). Overall, 112 patients were recruited, of whom 58% had type 1 diabetes. Linear regression analysis showed an intercept of 17.7, statistically different from 0 (p<0.0001). The slope was 0.956, and the Pearson correlation coefficient was 0.95. A MARE of 12.1% (SD=11.8%) was obtained, with a greater deviation of the forearm values from the fingertip ones in the hypoglycemic range (MARE=22.3%; SD=21.7%). The Bland-Altman bias plot showed a mean bias of 10.2 mg/dL (SD=23.1), with no correlation between mean difference and average BG levels (r=0.02). The EGA showed that 89.2% of the values fell in zone A, 10.4% in zone B, and 0.4% in zone C. The vast majority of patients (71%) declared that the collection of blood from the forearm caused no pain or less pain than the traditional site. Only 17% of the patients declared that it was impossible to obtain any blood from the forearm, while 63% reported with satisfaction that the quantity requested was small. At the end of the study period, 32% of the participants indicated the forearm as the preferred test site. Alternative site testing on the arm, with a BG meter that requires only a very small drop of blood, is feasible and reliable under routine clinical conditions. When testing with the express purpose of detecting hypoglycemia, the finger still remains the recommended test site.