| Objective: To evaluate the accuracy of continuous glucose monitoring system(CGMS) compared with venous blood glucose measurement in type 2 diabetic patients.Methods: A total of 42 newly diagnosed type 2 diabetic patients from Dalian Central Hospital in patient endocrine in March 2008 to March 2009 participated in this study. For each subject, glucose sensors were inserted into the subcutaneous tissue of the abdominal wall at the first. The following morning, after an overnight (12h) fast, subjects were admitted to an intravenous glucose tolerance test(IVGTT). Briefly, injected in the elbow vein with 50% of the glucose solution 50ml, injection time was 3 minutes. To push the bolus injection before and after the contralateral elbow as 3,5,7,10 minute, venous blood glucose and insulin were measured. Then given to the infusion of insulin, the first infusion rate was 3mU?kg-1?min-1, the hyperinsulinemia euglycemia clamp test was begun after the pilot phase when the blood glucose dropped to 5.5 ~ 6mmol/L: The rate of insulin infusion(to "Priming-continous" approach) was standard, that was 1mU?kg-1?min-1; clamp time was generally 120 ~ 150 minutes. In the meantime, arterialized blood was sampled every 5 minute and blood glucose was determined, adjusting the clamp glucose infusion rate so close to the target blood glucose set 5mmol/L. Selected the 9 / 42 patients ( with no history of cerebrovascular and cardisvascular disease) to enable the glucose drop to lower than 3.9mmol/L and continued for 10 minutes following, and then infused the glucose to make the blood glucose normal, all the venous blood glucose measured were input by CGMS in real-time. Throughout the trial the patients were clear-headed, under a state of quiet.Results: (1) The overall value of the CGMS and the venous blood glucose level had a good correlation, correlation coefficient was 0.884(P<0.01), percentage of relative error was 4.97%. (2) The results of comparison venous blood glucose level based on group were as follows: When the venous blood glucose level≥4.0mmol/L, the correlation coefficients between the CGMS glucose values and the venous blood glucose values were all higher than 0.736(P<0.01), the two difference has no statistics significance(P > 0.05),percentages of relative error were within 12.0%; When the venous blood glucose level≤3.9mmol/L (altogether 28 spots), the correlation coefficient between them was only 0.541, the two difference has statistics significance(P<0.05), the relative error percentage reached as high as 27.4%. (3) The error grid analysis demonstrated 65.11% data to fall on the zone A, there were 98.34% data to fall on the zone A and the zone B, only 3 points (0.23%) fall on the zone C, 19 points (1.44%) fall on the zone D, had not the data to fall on the zone E. The data in zone D data was lower than 3.9mmol/L.Conclusions: When the venous blood glucose level≥4.0mmol/L, CGMS could reflect the blood glucose relatively accurately the real level; But when the venous blood glucose level≤3.9mmol/L, the CGMS accuracy was weakened. In this case, venous blood glucose should be thought of a standard for the measurement of clinical blood glucose level. |
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