Normal Fasting Plasma Glucose Levels and Type 2 Diabetes
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《新英格兰医药杂志》
To the Editor: Tirosh et al. (Oct. 6 issue)1 found higher fasting glucose levels within the normoglycemic range to be a risk factor for type 2 diabetes in young men. They collected blood in fluoride tubes, which were sent to the laboratory uncentrifuged. However, levels of glucose continue to decrease for up to four hours in fluoride tubes and can drop by variable amounts, sometimes exceeding 9 mg per deciliter.2,3 Most of this decrease occurs in the two hours immediately after venipuncture.2 A change of this magnitude could straddle two of the four top population quintiles described by Tirosh et al. Measurement bias, such as that introduced by failure to separate plasma from cells immediately or by the inherent variability of calibration, limits the use of simple cutoffs for plasma glucose levels in the identification of patients at risk for diabetes. We have suggested methods to minimize errors in venous glucose measurement.4,5
Raymond Gambino, M.D.
Samuel Reichberg, M.D., Ph.D.
Joyce G. Schwartz, M.D.
Quest Diagnostics
Lyndhurst, NJ 07071
doclab@aol.com
References
Tirosh A, Shai I, Tekes-Manova D, et al. Normal fasting plasma glucose levels and type 2 diabetes in young men. N Engl J Med 2005;353:1454-1462.
Chan AY, Swaninathan R, Cockram CS. Effectiveness of sodium fluoride as a preservative of glucose in blood. Clin Chem 1989;35:315-317.
Sidebottom RA, Williams PR, Kanarek KS. Glucose determinations in plasma and serum: potential error related to increased hematocrit. Clin Chem 1982;28:190-192.
Schwartz JG, Reichberg SB, Gambino RS. Glucose testing variability and the need for an expert oversight committee. CAP Today 2005;19:12-16.
Sacks DB, Bruns DE, Goldstein DE, Maclaren NK, McDonald JM, Parrott M. Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus. Clin Chem 2002;48:436-472.
The authors reply: The technical point raised by Gambino and colleagues is well taken but is unlikely to have substantially affected our conclusions. Though potentially valuable for accurate blood glucose measurements in the future, new techniques such as those cited by Gambino and colleagues were not available to us nor to most investigators in studies that have provided cutoff definitions for blood glucose values. With a maximum of two hours between venipuncture and sample analysis, an expected rate of 14.1 percent impaired fasting-glucose levels was observed in our cohort of healthy young men.1,2 The suggested possibility of an underestimation of 9 mg per deciliter in our blood glucose measurements would have raised this rate to more than 50 percent, a highly unlikely finding in such a population. Furthermore, the association between fasting plasma glucose and incident diabetes increased progressively, suggesting a linear trend from the lowest quintile. Finally, common clinical practice in primary care clinics relies on blood glucose measurements performed in a manner similar to the approach that we used. Therefore, we think that our results are probably relevant to the general practitioner in the assessment of the risk of diabetes in healthy young adults.
Amir Tirosh, M.D., Ph.D.
Sheba Medical Center
52621 Tel-Hashomer, Israel
amirt@bgu.ac.il
Iris Shai, R.D., Ph.D.
Assaf Rudich, M.D., Ph.D.
Ben-Gurion University
84103 Beersheba, Israel
References
DECODE Study Group. Age- and sex-specific prevalences of diabetes and impaired glucose regulation in 13 European cohorts. Diabetes Care 2003;26:61-69.
Qiao Q, Hu G, Tuomilehto J, et al. Age- and sex-specific prevalence of diabetes and impaired glucose regulation in 11 Asian cohorts. Diabetes Care 2003;26:1770-1780.
Raymond Gambino, M.D.
Samuel Reichberg, M.D., Ph.D.
Joyce G. Schwartz, M.D.
Quest Diagnostics
Lyndhurst, NJ 07071
doclab@aol.com
References
Tirosh A, Shai I, Tekes-Manova D, et al. Normal fasting plasma glucose levels and type 2 diabetes in young men. N Engl J Med 2005;353:1454-1462.
Chan AY, Swaninathan R, Cockram CS. Effectiveness of sodium fluoride as a preservative of glucose in blood. Clin Chem 1989;35:315-317.
Sidebottom RA, Williams PR, Kanarek KS. Glucose determinations in plasma and serum: potential error related to increased hematocrit. Clin Chem 1982;28:190-192.
Schwartz JG, Reichberg SB, Gambino RS. Glucose testing variability and the need for an expert oversight committee. CAP Today 2005;19:12-16.
Sacks DB, Bruns DE, Goldstein DE, Maclaren NK, McDonald JM, Parrott M. Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus. Clin Chem 2002;48:436-472.
The authors reply: The technical point raised by Gambino and colleagues is well taken but is unlikely to have substantially affected our conclusions. Though potentially valuable for accurate blood glucose measurements in the future, new techniques such as those cited by Gambino and colleagues were not available to us nor to most investigators in studies that have provided cutoff definitions for blood glucose values. With a maximum of two hours between venipuncture and sample analysis, an expected rate of 14.1 percent impaired fasting-glucose levels was observed in our cohort of healthy young men.1,2 The suggested possibility of an underestimation of 9 mg per deciliter in our blood glucose measurements would have raised this rate to more than 50 percent, a highly unlikely finding in such a population. Furthermore, the association between fasting plasma glucose and incident diabetes increased progressively, suggesting a linear trend from the lowest quintile. Finally, common clinical practice in primary care clinics relies on blood glucose measurements performed in a manner similar to the approach that we used. Therefore, we think that our results are probably relevant to the general practitioner in the assessment of the risk of diabetes in healthy young adults.
Amir Tirosh, M.D., Ph.D.
Sheba Medical Center
52621 Tel-Hashomer, Israel
amirt@bgu.ac.il
Iris Shai, R.D., Ph.D.
Assaf Rudich, M.D., Ph.D.
Ben-Gurion University
84103 Beersheba, Israel
References
DECODE Study Group. Age- and sex-specific prevalences of diabetes and impaired glucose regulation in 13 European cohorts. Diabetes Care 2003;26:61-69.
Qiao Q, Hu G, Tuomilehto J, et al. Age- and sex-specific prevalence of diabetes and impaired glucose regulation in 11 Asian cohorts. Diabetes Care 2003;26:1770-1780.