We report the brief experience of the Nephrology Center located in a "no-COVID" Hospital in Massa Marittima. We describe the actions taken to prevent the transmission of the virus SARS-CoV-2 among hemodialysis patients and healthcare workers and the methods for diagnosing COVID-19, with particular attention to serological tests and nasopharyngeal swabs in asymptomatic subjects. The detection of IgM and IgG antibodies through the serological test performed on 34 patients, all negative for nasopharyngeal swabs, showed positivity in 41,18% of cases. These have been classified as false positives following repeated negative nasopharyngeal swabs, the evaluation of clinical and epidemiological history and of clinical manifestations and, finally, a second serological test performed after 18 days, which resulted negative for all patients. Interpreting serological tests is not easy; the strategies for diagnosis should include clinical and epidemiological history and clinical manifestations, as well as the results of confirmation tests and the evaluation over a precise observation period. Otherwise, there is a risk of considering as protected by antibodies subjects that are in fact false positives.