Our study observed a prevalence of low levels of ANA among 25.6% COVID-19 patients. This was less than half of the normal background prevalence of ANA in patients in Kocaeli, which was approximately 57.3% 11. We also observed a prevalence of ANA of 22.2% in hospitalized COVID-19 patients. The ANA prevalence between studies in hospitalized COVID-19 patients were divergent, ranging between 34.5% and 50%. (Table 2). A report from Greece demonstrated that the positive rate of ANA was 34.5% in hospitalized patients 10. In Italy, 34 COVID-19 cases were analyzed, and the detection rate of ANA was 35.3% 8, 9. Apart from those studies, a report from Japan, one of two (50%) severe covid-19 cases were found ANA positive 7. All studies used indirect immunofluorescence (IIF) as method for serum ANA detection. The higher rates of ANA from Japan might be due to the characteristics of the two cases demographic, environmental or genetic factors. In a previous study with multiplex immunoassay the ANA was found 25.0% of covid-19 patients, three third of the cases were from intensive care unit 4. One of the reasons for the different results among the current and the previous studies might be related to the small study groups. The varying rates of ANA prevalence from different parts of the world might also be due to the characteristics of the study population demographic, environmental or genetic factors.
Age seems to be the most important factor associated with a more severe course of COVID-19 12. However, in this study, no relation was found between age and ANA positivity. Male gender has also been described as an important risk factor for a more severe course and higher mortality. In this study, male gender was correlated with ANA positivity, but there was no correlation between severe course of infection and ANA positivity.
The positive rate of ANA IIF Hep-2 test was different between our previous 11 and current studies (57.3–25.6%). The female to male ratio was also higher (4.6 vs 3.4). Comparing ANA patterns between old and current studies, the rate of mixed (10.0% vs 21.3%) patterns was found to decrease. The mixed patterns in our study referred to the existence of two or more patterns. The mixed patterns could provide a hint for SSc (43.4%) and SLE (27.8%) 13. Though, in this study, ANA pattern and titer were found irrelevant with the severe course of infection.
There are a few limitations of this study. The study population might not reflect all aspects of target population. We do not have the detailed clinical data needed to capture all possible comorbidities. The retrospective design of our study did not allow for the analysis interaction between anti-covid antibodies and ANA. The follow-up period of the ANA positive patients was limited. In general, the study data reflects characteristics of geographic properties. Further studies with larger populations are compulsory to interpret the study results in detail.
In conclusion, although males were more prone to produce ANA during COVID-19 infection, this was not correlated with severe course. It would be interesting for future studies to explore in greater detail whether severe course of COVID-19 infection in male is correlated with ANA positivity. Future studies are also needed to address the possible role of host and environmental factors in autoantibody formation in COVID-19 infection.