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what changes with the Ministry circular


For the diagnosis of Covid-19 cases, the molecular buffer remains the gold standard ma rapid antigen tests, if equipped with “overlapping sensitivity and specificity”, such as those of the latest generation, they represent “a valid alternative“. This is indicated by a new circular from the Ministry of Health “Updating the definition of the Covid-19 case and testing strategy” which recognizes the partial validity of antigen tests, in consideration of the evolution of the epidemiological situation and the indications of the European Center for Disease Prevention and Control (ECDC).

Covid-19 diagnosis criteria

In addition to the diagnostic criteria, in the document they are outlined the clinical criteria case definition of Covid-19, which include the presence of at least one of the following symptoms: cough, fever, shortness of breath (dyspnoea) and acute onset of abnormia (loss of the sense of smell), ageusia or dyseusia (loss of sense of taste). Other less specific symptoms may include headache, chills, myalgia, asthenia, vomiting and / or diarrhea.

The radiological criteria have also been specified, with a framework compatible with Covid-19, and epidemiological criteria therefore, at least one of the following two links must be present: a) close contact with a confirmed case of Covid-19 in the 14 days preceding the onset of symptoms; if the case does not show symptoms, contact is defined as a person who has had contact with the index case in a period of time ranging from 48 hours before the collection of the sample that led to the confirmation and up to 14 days after or until the moment diagnosis and case isolation; b) be a resident / operator, in the 14 days prior to the onset of symptoms, in health (hospital and territorial) and socio-welfare / social-health contexts such as RSA, long-term care, closed or semi-closed communities (eg prisons, reception centers for migrants) , in which there is transmission of SARS-CoV-2.

Use of rapid antigen tests

For the case confirmation of Covid-19, the subject must in any case satisfy one following laboratory criteria: therefore there must be a) a detection of Sars-Cov-2 nucleic acid in a clinical sample, or b) a detection of Sars-Cov-2 antigen in a clinical sample, as defined by the use of antigen tests quick.

As stated, the main novelty of the circular concerns this second point, namely the partial green light for the use of rapid antigen tests, the results of which “must be interpreted on the basis of the epidemiological situation of the population studied” in the case of use of first and second generation rapid antigenic tests (immunochromatographic assays), whose sensitivity and specificity “tend to be lower than those of the molecular test and they vary considerably according to the time of sampling “.

As for the rapid antigen tests last generation (immunofluorescence with microfluidic reading) which, as mentioned, have proven to have sensitivity and specificity almost comparable to molecular tests, these “turn out to be a valid alternative” to molecular tests. If neither the latest generation rapid antigenic assays nor molecular tests are available, the Ministry recommends the use of antigenic tests that have minimum performance requirements, therefore sensitivity greater than or equal to 80% and specificity equal to or greater than 97%.

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