The right test at the right time

• RT-PCR is the laboratory test of choice. It is the most sensitive test for this purpose. A positive or negative result from a RT-PCR test is likely to be true. The method selected must be against specific genetic sequences of SARS-CoV-2.

• In clinical situations in which RT-PCR is not available within the necessary time window, or which require a rapid turnaround to speed up the management of acute patients, we recommend the use of antigen tests. The tests should be designed to detect at least Protein S of SARS-CoV-2 and to be positive for samples of medium and high viral load. In this clinical situation, it is mandatory to confirm negative results with RT-PCR.

• Although not recommended for diagnostic purposes, we support the hypothesis of additional serological laboratory testing for antibodies in patients that are symptomatic for a prolonged time period, as well as in patients with a clinical diagnosis of Covid-19 and several negative results for RT-PCR specific tests.

Recommendations for detecting infections in individuals without symptoms and tracing the spread of SARS-CoV-2 through their contacts.

a) Investigation of asymptomatic carriers

• The laboratory test of choice is RT-PCR. It is the most sensitive test for this purpose. A positive or negative result from a RT-PCR test is likely to be true. The method selected must be addressed to genes specific of SARS-CoV-2.

b) Investigation of asymptomatic contacts

• The laboratory test of choice is RT-PCR. It is the most sensitive test for this purpose. A positive or negative result from a RT-PCR test is likely to be true. The method selected must be addressed to genes specific of SARS-CoV-2.

• Specific IgG tests for close contacts showing negative RT-PCR results, after quarantine.

• No Covid-19 specific tests during the follow up of hospitalized patients are recommended. Clinical follow-up and laboratory tests according to patient progress are recommended.

• In this phase of such an unknown disease, a request for specific antibodies to understand the seroconversion response may be considered.

• Hospitalized patients should be discharged according to clinical criteria. Many countries mandate at least two negative tests in the 24-hour period before discharge, however, these negative results do not provide assurance that the patient is not able to infect others.
• In this phase of such an unknown disease and for academic purposes, we recommend testing RT-PCR and specific antibodies at discharge. The same protocol applies to those patients in home quarantine.

• For first line healthcare professionals, we recommend periodical testing by means of SARS-CoV-2 RT
  PCR (range between 7-10 days) and IgG antibodies (range between 14-21 days). This procedure improves the occupational safety for healthcare professionals as well as the safety of Covid-19 patients and patients that do not seek medical consultation in due time for fear of infection.