Biomarkers - Diabetes

Diabetes

This section documents TILDA biomarkers used to characterise longer-term glycaemic status and diabetes-related metabolic health.

Diabetes Biomarkers

Click each heading to expand details of this biomarker.

Overview

What is it? Glycosylated haemoglobin (HbA1c) is formed when glucose binds to haemoglobin in red blood cells. As red blood cells typically circulate for around three months, HbA1c reflects average blood glucose levels over the preceding 2–3 months.

Research relevance: Can be used to investigate long-term glycaemic control and metabolic health, including the identification and study of prediabetes and diabetes and their associations with health outcomes.

Sample type: Frozen K2EDTA buffy coat/plasma (Wave 1) and K2EDTA blood plasma (Wave 3)

Sample Collection / Handling

Samples were isolated from 10 mL of fresh whole blood, maintained at 2–4°C for 24–48 hours after blood collection and subsequently frozen at −80°C.

Assay / Measurement

Method: Reversed-phase cation-exchange chromatography, traceable to the internationally agreed International Federation of Clinical Chemistry (IFCC) standard.

Equipment / analyser: Waves 1 and 3: A. Menarini Diagnostics A1c HA-8180V analyser.

Laboratory: Waves 1 and 3: Biochemistry Department, Laboratory Medicine (LabMed), St James’s Hospital, Dublin.

Measurement Characteristics

Characteristic Value
Units nmol/L
Measurement range 9-195 mmol/mol
Lower detection limit 9.0 mmol/mol
Assay CoV 0.007

Collection Waves

Biomarker Wave 1 Wave 2 Wave 3 Wave 4 Wave 5 Wave 6
Glycosylated Haemoglobin X X X

Reference

  • National Institute of Diabetes and Digestive and Kidney Diseases (2024) The A1C Test & Diabetes. Available at: https://www.niddk.nih.gov/health-information/diagnostic-tests/a1c-test

Example TILDA Papers

  • Leahy S, O’Halloran AM, O’ Leary N, Healy M, McCormack M, Kenny RA, O’ Connell J. Prevalence and correlates of diagnosed and undiagnosed type 2 diabetes mellitus and pre-diabetes in older adults: Findings from the Irish Longitudinal Study on Ageing (TILDA). Diabetes Res Clin Pract. 2015 Dec; 110(3):241-9. https://doi.org/10.1016/j.diabres.2015.10.015.