title: The relationship between fasting plasma glucose and HbA1c during intensive periods of glucose control in antidiabetic therapy.
abstract: OBJECTIVE
  HbA1c measurements are typically less variable than fasting plasma glucose (FPG) for diagnosing diabetes, and for assessment of progress on glucose control therapy. However HbA1c reaches steady-state relative to average plasma glucose over about 120 days. HbA1c thus overestimates average FPG during first three months of starting therapy in newly diagnosed diabetic patients, and care needs to be exercised in interpreting HbA1c measurements during this period. At steady-state excellent regression exists between HbA1c and FPG. We hypothesize that this regression can also be used to obtain reliable estimates of HbA1c relative to FPG at 4 and 8 weeks following the onset of therapy.
  
  
  METHODS
  We collected FPG and HbA1c data of type 2 diabetic patients over the first 8 weeks of starting antidiabetic treatment. We fit linear and nonlinear regression models to steady-state data, and estimated how much measured HbA1c deviates at 4 and 8 weeks from these theoretical relations.
  
  
  RESULTS
  If measured HbA1c is decremented by 0.7% (8 mmol/mol) at 4 weeks and 0.3% (3 mmol/mol) at 8 weeks, this corrected HbA1c is a better predictor of the corresponding FPG. Using hyperbolic regression, corrections to HbA1c are 0.5 and 0.1% (5 and 1 mmol/mol), respectively.
  
  
  CONCLUSIONS
  With the corrections proposed here, HbA1c measurements can be better interpreted in the early weeks of antidiabetic treatment.
authors.affiliation: Department of Mathematics, Indian Institute of Science Education and Research Pune, Pune 411008, India. Electronic address: amlan.barua@iiserpune.ac.in.
authors.forename: Amlan
authors.initials: A
authors.lastname: Barua
authors.affiliation: Department of Zoology, University of Pune, Pune 41107, India.
authors.forename: Jhankar
authors.initials: J
authors.lastname: Acharya
authors.affiliation: Department of Zoology, University of Pune, Pune 41107, India.
authors.forename: Saroj
authors.initials: S
authors.lastname: Ghaskadbi
authors.affiliation: Mathematics and Biology, Indian Institute of Science Education and Research Pune, Pune 411008, India.
authors.forename: Pranay
authors.initials: P
authors.lastname: Goel
mesh_terms: D015415:Biomarkers / Q000378:metabolism*; D001786:Blood Glucose / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis* / Q000188:drug therapy*; D005215:Fasting / Q000097:blood*; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D012044:Regression Analysis; D013997:Time Factors
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human
keywords: Glycated hemoglobin; Nonlinear regression analysis; Type 2 diabetes mellitus