Interstitial Glucose and Lactate Levels Are Inversely Correlated With the Body Mass Index: Need for In Vivo Calibration of Glucose Sensor Results With Blood Values in Obese Patients.

Background: Continuously measured glucose and lactate levels in interstitial fluid (ISF) may markedly differ from their respective blood levels.

Methods: Combining microdialysis with a bioanalytical microsystem, the interstitial glucose and lactate concentrations of eight male volunteers with different body mass index (BMI) were monitored during a 2-fold glucose tolerance test over the period of three hours.

Results: Significant correlations were found between abdominally measured sensor results and reference measurements ( R = .967 for glucose and R = .936 for lactate, P < .05). The physiological delay of the abdominally observed glucose appearance in the ISF correlated positively with the BMI ( R = .787, P < .05). The relative in vivo recovery of glucose and lactate was inversely proportional to the BMI of the volunteers ( R = .540 for glucose, R = .609 for lactate, P < .05). One subject with a BMI of > 34 kg/m showed abdominally as well as the antebrachially significantly reduced tissue glucose values compared to blood glucose values ( P < .001).

Conclusions: A very good correlation between abdominally measured sensor results and the results of the reference method verified the reliability of the BioMEMS. The abdominally measured glucose level in ISF decreased significantly with increasing BMI. Therefore, an in vivo calibration of glucose levels in ISF with blood levels seems to be necessary especially in markedly obese subjects.