This Article  • Full text  • PDF  • Send to a friend  • Save in My Folder  • Save to citation manager  • Permissions  Citing Articles  • Citation map  • Citing articles on HighWire  • Citing articles on ISI (2)  • Contact me when this article is cited  Related Content  • Similar articles in this journal  Topic Collections  • Diabetes Mellitus  • Diagnosis  • Nutritional and Metabolic Disorders, Other  • Alert me on articles by topic

Elizabeth Selvin, PhD, MPH; Ciprian M. Crainiceanu, PhD; Frederick L. Brancati, MD, MHS; Josef Coresh, MD, PhD

Arch Intern Med. 2007;167(14):1545-1551.

Background  Short-term variability in measures of glycemia has important implications for the diagnosis of diabetes mellitus and the conduct and interpretation of epidemiologic studies. Our objectives were to characterize the within-person variability in fasting glucose, 2-hour glucose, and hemoglobin A_1c (HbA_1c) levels and to assess the impact of using repeated measurements for classification of diabetes.

Methods  We analyzed repeated measurements from 685 fasting participants without diagnosed diabetes from the National Health and Nutrition Examination Survey III Second Examination, a substudy conducted from 1988 to 1994 in which repeated examinations were conducted approximately 2 weeks after the original examination.

Results  Two-hour glucose levels had substantially more variability (within-person coefficient of variation [CV_w], 16.7%; 95% confidence interval [CI], 15.0 to 18.3) compared with either fasting glucose (CV_w, 5.7%; 95% CI, 5.3 to 6.1) or HbA_1c (CV_w, 3.6%; 95% CI, 3.2 to 4.0) levels. The proportion of persons with a fasting glucose level of 126 mg/dL or higher (to convert to millimoles per liter, multiply by 0.0555) on the first test who also had a second glucose level of 126 mg/dL or higher was 70.4% (95% CI, 49.8% to 86.2%). Results were similar using the 2-hour glucose cutoff point of 140 mg/dL or higher. The prevalence of undiagnosed diabetes using a single fasting glucose level of 126 mg/dL or higher was 3.7%. If a second fasting glucose level of 126 mg/dL or higher was used to confirm the diagnosis (American Diabetes Association guidelines), the prevalence decreased to 2.8% (95% CI, 1.5% to 4.0%), a 24.4% decrease.

Conclusions  We found high variability in 2-hour glucose levels relative to fasting glucose levels and high variability in both of these relative to HbA_1c levels. Our findings suggest that studies that strictly apply guidelines for the diagnosis of diabetes (2 glucose measurements) may arrive at substantially different prevalence estimates compared with studies that use only a single measurement.

Author Affiliations: Departments of Epidemiology (Drs Selvin, Brancati, and Coresh) and Biostatistics (Drs Crainiceanu and Coresh), Johns Hopkins Bloomberg School of Public Health, and Welch Center for Prevention, Epidemiology and Clinical Research (Drs Selvin, Brancati, and Coresh) and Department of Medicine (Drs Brancati and Coresh), Johns Hopkins School of Medicine, Baltimore, Maryland.

THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES

Brief Communication: Clinical Implications of Short-Term Variability in Liver Function Test Results
Lazo et al.
ANN INTERN MED 2008;148:348-352.
ABSTRACT | FULL TEXT  

Glucose: A Simple Molecule That Is Not Simple to Quantify
Gambino
Clin. Chem. 2007;53:2040-2041.
FULL TEXT