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Diabetologia

, Volume 39, Issue 3, pp 298–305 | Cite as

Intra-individual variation of glucose, specific insulin and proinsulin concentrations measured by two oral glucose tolerance tests in a general Caucasian population: the Hoorn Study

  • J. M. Mooy
  • P. A. Grootenhuis
  • H. de Vries
  • P. J. Kostense
  • C. Popp-Snijders
  • L. M. Bouter
  • R. J. Heine
Originals

Summary

We studied the intra-individual variation in plasma glucose, specific serum insulin and serum pro-insulin concentrations, measured by two 75-g oral glucose tolerance tests in an age, sex, and glucose tolerance stratified random sample from a 50–74-year-old Caucasian population without a history of diabetes mellitus. The intra-individual variation was assessed by the standard deviation of the test-retest differences (SDdif). For subjects with normal (n=246), impaired glucose tolerance (n=198), and newly detected diabetes (n=80) classified at the first test, the following (SDdif/median level of individual average scores) were found: fasting glucose: 0.4/5.4, 0.5/5.9 and 0.7/7.2 mmol/l; 2-h glucose: 1.3/5.6, 1.8/8.5 and 2.3/12.8 mmol/l; fasting insulin: 23/76, 32/89 and 30/ 116 pmol/l; 2-h insulin: 190/303, 278/553 and 304/626 pmol/l; fasting proinsulin: 4/8, 6/13 and 9/18 pmol/l; 2-h proinsulin: 19/49, 23/84 and 33/90 pmol/l, respectively. In both glucose, proinsulin and insulin concentrations the total intra-individual variation was predominantly determined by biological variation, whereas analytical variation made only a minor contribution. The SDdif can easily be interpreted, as 95% of the random test-retest differences will be less than 2 · SDdif, or in terms of percentage, less than (2 · SDdif/median level of individual average scores) · 100. Therefore, for subjects with normal glucose tolerance, 95% of the random test-retest differences will be less than 15% (fasting glucose), 46% (2-h glucose), 61% (fasting insulin), 125% (2-h insulin), 100% (fasting proinsulin) and 78% (2-h proinsulin) of the median value of the individual average scores. No substantial independent association of either age, gender or obesity with the intra-individual variation in glucose, proinsulin, or insulin concentrations was found.

Keywords

Intra-individual variation glucose specific insulin proinsulin oral glucose tolerance test reproducibility 

Abbreviations

OGTT

Oral glucose tolerance test

NGT1st, IGT1st new DM1st

normal glucose tolerance, impaired glucose tolerance and newly detected diabetes mellitus, respectively, as classified at first OGTT

SDdif

standard deviation of the difference scores

CVintra

intra-individual coefficient of variation

CVbi

biological intra-individual coefficient of variation

CVa

analytical intra-individual coefficient of variation

Cl95

95% confidence interval

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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • J. M. Mooy
    • 1
  • P. A. Grootenhuis
    • 1
  • H. de Vries
    • 1
    • 2
  • P. J. Kostense
    • 1
    • 3
  • C. Popp-Snijders
    • 4
  • L. M. Bouter
    • 1
    • 3
  • R. J. Heine
    • 1
    • 5
  1. 1.Institute for Research in Extramural MedicineVrije UniversiteitBT AmsterdamThe Netherlands
  2. 2.Department of General Practice, Nursing Home Medicine and Social MedicineVrije UniversiteitAmsterdamThe Netherlands
  3. 3.Department of Epidemiology and BiostatisticsVrije UniversiteitAmsterdamThe Netherlands
  4. 4.Department of Clinical Chemistry and EndocrinologyVrije UniversiteitAmsterdamThe Netherlands
  5. 5.Department of Internal Medicine of Vrije UniversiteitAmsterdamThe Netherlands

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