Clinical Impact of Prandial State, Exercise, and Site Preparation on the Equivalence of Alternative-Site Blood Glucose Testing

Abstract

OBJECTIVE—To determine whether clinically significant differences exist in fasting blood glucose (BG) at the forearm, palm, and thigh relative to the fingertip; to assess the impact of prandial status by comparing BG between alternative sites and the fingertip at several time intervals after carbohydrate intake; to assess the effects of moderate brief exercise on site-to-site differences in BG; to evaluate the impact of site preparation by local rubbing on alternative-site testing (AST) equivalence; and to determine levels of perceived pain and satisfaction associated with AST. RESEARCH DESIGN AND METHODS—Fasting BG was measured using the One Touch Ultra (LifeScan, Milpitas, CA) at the fingertip, palm, thigh, and each forearm (with local rubbing) in 86 patients with type 2 diabetes. A 40-g carbohydrate meal was consumed and BG was again measured from each site at 60, 90, and 120 min postmeal, with an additional forearm test at 90 min without local rubbing. Patients then exercised for 15 min with repeat BG at each site. Differences in BG between sites were assessed using repeated-measures ANOVA and regression analyses. RESULTS—Significant differences in BG at alternative sites were found 60 min postmeal (P = 0.0003) and postexercise (P = 0.037). Specifically, clinically significant differences (expressed as percent difference from the fingertip) at 60 min include −8.8 ± 10.8% at the forearm and −13.7 ± 10.7% at the thigh, and postexercise +19.1 ± 19.1% at the forearm and +15.6 ± 22.6% at the thigh. However, no significant differences were observed between sites in either the fasting state or at 90 and 120 min postmeal. The dynamic results suggest a time lag in equilibration of forearm and thigh BG during periods of rapid glucose change. Palm and fingertip BG test results were similar at all time points. CONCLUSIONS—AST results are consistent with fingertip BG results in both the fasting state and 2 h postmeal; no benefit from site preparation by local rubbing was noted. However, testing at sites other than the hand cannot be recommended 1 h postmeal or immediately after exercise. AST is equivalent and appropriate for use at testing times commonly used in clinical practice.