SARS-CoV-2 humoral immunity is associated with elevated hemoglobin A1c

This prospective study assessed relationships between COVID-19, humoral immunity, and common laboratory test results.

Blood and urine were collected from adults with clinical SARS-CoV-2 test results before August 2021: nucleic acid amplification (NAA) tests and antinucleocapsid protein (αN) serology. Measurements were made of αN and 13 laboratory tests, and results were compared across groups defined by NAA and αN status.

Glycated hemoglobin (HbA1c) and platelet counts were clinically significantly higher among individuals who had COVID-19 than in individuals without evidence of COVID-19. Hemoglobin was more abnormal among patients without evidence of COVID-19. Glycated hemoglobin results were also much higher among patients with prior positive NAA and current or prior positive αN results than in individuals with negative αN results. No other statistically significant associations between NAA or αN and abnormal laboratory results were found.

Elevated HbA1c results were associated with prior positive NAA findings combined with positive αN results but not with negative αN results. Further investigation into the association of dysregulated glycemic control with humoral immunity to natural infection is warranted, given the well-documented increase in incidence in type 1 and type 2 diabetes following COVID-19. Prior positive NAA results were also associated with a few nonspecific abnormalities of the complete blood cell count.