Is there a seasonal variation in HbA1c in Australia?
Hui Yi Ng, Rowena Hockings, Gary Gary Morris, Robert Moses
Abstract
Background
A recent publication has shown that the prevalence of gestational diabetes mellitus (GDM) diagnosed with a glucose tolerance test (GTT) has a significant seasonal variation. The HbA1c has been proposed as an alternate method for testing of GDM.
Aims
Numerous reports indicate that in the Northern Hemisphere the HbA1c is higher in winter. The aim of this study was to assess if there was a seasonal variation in the HbA1c in a temperate climate.
Methods
Southern IML Pathology (SIML) is the major provider of pathology services in Wollongong and surrounding areas. De-identified data were obtained from SIML from January 2011 to December 2015. The data included the date of collection, date of birth, gender and HbA1c.
Results
A total of 203,170 HbA1c results were available for analysis. The median HbA1c was 6.6 per cent (48mmol/mol) for each season. While these differences were statistically significant (due to the large numbers used for analysis), it was felt unlikely to be of clinical significance. There was also no difference in the median HbA1c in females with HbA1c ≤6.0 per cent; the probable range during pregnancy.
Conclusion
Whereas in the Northern hemisphere the HbA1c does exhibit seasonal variation, this was not apparent in a temperate climate. Specific data are required during pregnancy. HbA1c could be considered as an alternative diagnostic test during pregnancy to potentially overcome the changes in prevalence with seasons with GTT.
Full Text:
A recent publication has shown that the prevalence of gestational diabetes mellitus (GDM) diagnosed with a glucose tolerance test (GTT) has a significant seasonal variation. The HbA1c has been proposed as an alternate method for testing of GDM.
Aims
Numerous reports indicate that in the Northern Hemisphere the HbA1c is higher in winter. The aim of this study was to assess if there was a seasonal variation in the HbA1c in a temperate climate.
Methods
Southern IML Pathology (SIML) is the major provider of pathology services in Wollongong and surrounding areas. De-identified data were obtained from SIML from January 2011 to December 2015. The data included the date of collection, date of birth, gender and HbA1c.
Results
A total of 203,170 HbA1c results were available for analysis. The median HbA1c was 6.6 per cent (48mmol/mol) for each season. While these differences were statistically significant (due to the large numbers used for analysis), it was felt unlikely to be of clinical significance. There was also no difference in the median HbA1c in females with HbA1c ≤6.0 per cent; the probable range during pregnancy.
Conclusion
Whereas in the Northern hemisphere the HbA1c does exhibit seasonal variation, this was not apparent in a temperate climate. Specific data are required during pregnancy. HbA1c could be considered as an alternative diagnostic test during pregnancy to potentially overcome the changes in prevalence with seasons with GTT.
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