The relationship between glycated haemoglobin levels and the risk of Giant Cell Arteritis – A case-control study

Chetan Mukhtyar, Holly Myers, Colin Jones, Ketan Dhatariya

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Abstract

Objectives

The EULAR core dataset for observational studies in giant cell arteritis (GCA) does not include glycated haemoglobin (HbA1c). A multivariable score to stratify pre-test probability of GCA also does not include HbA1c. There have been contradictory reports about Diabetes Mellitus (DM) being a risk factor for GCA. We report the first study analysing the relationship of pre-diagnosis HbA1c with the risk of GCA.

Methods
This was a single centre retrospective case-control study conducted in Norfolk, UK. All GCA cases were diagnosed with imaging or biopsy. Each case was assigned 2 age and gender-matched controls. The primary outcome measure was the glycaemic status (HbA1c categorised into euglycaemia, pre-diabetes, DM) at diagnosis between cases and controls. HbA1c between two groups was compared using the Mann-Whitney U test. The glycaemic categorisation was compared using the Chi-squared test.

Results
112 cases and 224 controls were included. The median (IQR) of HbA1c of cases and controls was 40 (37, 43) and 41 (39, 47) (p < 0.001) respectively. 10/112 cases and 52/224 controls had DM. Chi-square test demonstrates significant interaction between glycaemic state and GCA (p = 0.006). Individuals with DM had an odds ratio (95% CI) of 0.32 (0.13,0.74) (p = 0.008) of having GCA compared to euglycaemic individuals.

Conclusion
HbA1c in the diabetic range reduces probability of GCA. HbA1c should be considered in any multivariable score to calculate risk of GCA, and in future development of diagnostic and classification criteria. There is need for an epidemiological study looking at the possibility of a protective nature of DM against GCA or whether it is just a mimic.
Original languageEnglish
Article numberrkaa018
JournalRheumatology Advances in Practice
Volume4
Issue number2
Early online date28 May 2020
DOIs
Publication statusPublished - Jun 2020

Keywords

  • Case-control study
  • Diabetes mellitus
  • Giant cell arteritis
  • Glycated haemoglobin
  • Risk stratification

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