Background:
COVID-19 MESHD epidemic has paralleled with the so called infodemic, where countless pieces of information have been disseminated on putative risk factors for
COVID-19 MESHD. Among those, emerged the notion that people suffering from
autoimmune diseases MESHD (
AIDs MESHD) have a higher risk of
SARS-CoV-2 infection MESHD. Methods: The cohort included all
COVID-19 MESHD cases residents in the Agency for Health Protection (AHP) of Milan that, from the beginning of the outbreak, developed a web-based platform that traced positive and negative cases as well as related contacts.
AIDs MESHD subjects were defined ad having one the following
autoimmune disease MESHD:
rheumatoid arthritis MESHD,
systemic lupus erythematosus MESHD,
systemic sclerosis MESHD, Sjogren disease,
ankylosing spondylitis MESHD,
myasthenia gravis MESHD,
Hashimoto's disease MESHD, acquired
autoimmune hemolytic anemia MESHD, and
psoriatic arthritis MESHD. To investigate whether
AID HGNC subjects are at increased risk of
SARS-CoV-2 infection MESHD, and whether they have worse prognosis than
AIDs MESHD-free subjects once infected, we performed a combined analysis of a test-negative design case-control study, a case-control with test-positive as cases, and one with test-negative as cases (CC-NEG). Results: During the outbreak, the Milan AHP endured, up to April 27th 2020, 20,364 test-positive and 34,697 test-negative subjects. We found no association between
AIDs MESHD and being positive to
COVID-19 MESHD, but a statistically significant association between
AIDs MESHD and being negative to
COVID-19 MESHD in the CC-NEG. If, as likely, test-negative subjects underwent testing because of
respiratory infection MESHD symptoms, these results imply that
autoimmune diseases MESHD may be a risk factor for
respiratory infections MESHD in general (including
COVID-19 MESHD), but they are not a specific risk factor for
COVID-19 MESHD. Furthermore, when infected by SARS-CoV-2,
AIDs MESHD subjects did not have a worse prognosis compared to non-
AIDs MESHD subjects. Results highlighted a potential unbalance in the testing campaign, which may be correlated to the characteristics of the tested person, leading specific frail population to be particularly tested.Conclusions: Lack of availability of sound scientific knowledge inevitably lead unreliable news to spread over the population, preventing people to disentangle them form reliable information. Even if additional studies are needed to replicate and strengthen our results, these findings represent initial evidence to derive recommendations based on actual data for subjects with
autoimmune diseases MESHD.