Research Professor/Co-Director of Diabetes Diagnostic Laboratory

Pathology and Anatomical Sciences




  • BS, Biology, State University of New York, Stonybrook, NY
  • PhD, Biology, Florida State University, Tallahassee, FL

Academic Appointments

  • Instructor, Departments of Pathology and Ophthalmology, University of Missouri-Columbia
  • Research Assistant Professor, Depts. of Pathology and Child Health, University of Missouri-Columbia

Research Description

The Diabetes Diagnostic Laboratory (DDL) is the site of the NGSP, an international program for standardization of HbA1c ( which is the most important test used to assess glycemic control in patients with diabetes. The NGSP maintains a laboratory network with reference method results that are based on landmark clinical trial data. The program certifies manufacturer methods for HbA1c and also certifies and monitors laboratories doing large studies and clinical trials where measurement of HbA1c is a key variable. Proficiency testing, primarily through the College of American Pathologists, is used to evaluate progress toward improved comparability of results among laboratories. Related research includes examination of stability of HbA1c and interferences (e.g. from Hb variants) with different assay methods.

Standardization of c-peptide is also in progress at the DDL. For c-peptide, as with HbA1c, purified or processed material shows significant matrix effects and cannot be used for calibration. The c-peptide program is evaluating the use of single donor and pooled specimens for use by manufacturers in the calibration of these assays. The laboratory is also establishing a reference method for c-peptide.


  • Glycated hemoglobin (HbA1c) methodology and Interferences
  • Standardization of HbA1c, insulin, and c-peptide measurements
  • Use of HbA1c and glycated plasma protein measurements for diabetes screening

Representative Publications

  1. Little RR, Rohlfing CL, Wiedmeyer HM, Myers GL, Sacks DB, Goldstein DE, for the NGSP Steering Committee. The National Glycohemoglobin Standardization Program: A Five-Year Progress Report. Clin Chem 47:1985-92, 2001.
  2. Little RR, Vesper H, Rohlfing CL, Ospina M, Sekineh SP, Roberts WL. Validation by a Mass Spectrometric Reference Method of Use of Boronate Affinity Chromatography to Measure Glycohemoglobin in the Presence of Hemoglobin S and C traits. Clin Chem, 51: 264-5, 2005.
  3. Little RR, Rohlfing CL, Tennill AL, Madsen RW, Polonsky KS, Greenbaum CJ, Myers GL, Palmer JP, Rogatsky E, Stein DT. Standardization of C-peptide Measurements. Clin Chem 54:1023-6, 2008.
  4. Little RR, Rohlfing CR, Hanson S, Connolly S, Higgins T, Weykamp C, D’Costa M, Luzzi V, Owen WE, Roberts WL. Effects of hemoglobin E and D traits on glycated hemoglobin (HbA1c) Measurements by twenty-three methods. Clin Chem 54: 1277-82, 2008.
  5. Rohlfing C, Connolly S, England J, Hanson S, Moellering C, Bachelder J, Little R. The effect of elevated fetal hemoglobin on HbA1c results: five common HbA1c methods compared to the IFCC reference method. Amer J Clin Path 129:811-4, 2008.
  6. Mongia SK, Little RR, Rohlfing CL, Hanson S, Roberts RF, Owen WE, D’Costa MA, Reyes CA, Luzzi VI, Roberts WL. Effects of Hemoglobin C and S Traits on the Results of 14 Commercial Glycated Hemoglobin Assays. Am J Clin Pathol 130:136-140, 2008.