Stopping the SARS-CoV2 spread is essential to control the pandemic cause by this virus. A great effort is being made to carry out surveillance, case detection and contact control protocols in order to detect and isolate those contagious subjects. Since both symptomatic and asymptomatic subjects can be contagious, a surveillance system based on the presence of symptoms is not enough, requiring to perform diagnostic tests in a large number of subjects, such as asymptomatic contacts or high-prevalence populations, and repeatedly. Moreover, the speed in obtaining results is crucial in order not to delay the isolations of positive subjects. The polymerase chain reaction (PCR) is an expensive test which requires specialized equipment and personnel with a delay in results of 24-48 hours. In addition, its high sensitivity can mean that subjects without infective capacity have a positive result. In contrast, antigen detection tests (ADTs) are cheap and easy to perform, having a result in few minutes. They have shown high sensitivity and specificity in symptomatic subjects, specially in the first week of symptoms when the viral load is high. This could be very useful for the study of asymptomatic contacts to detect those with potential contagiousness quick, easily and cheaply. However, there is no evidence to support the use of ADTs in this group of subjects. For this reason, the investigators propose to carry out a study to compare the diagnostic efficacy of ADTs versus PCR in the group of subjects considered to be close contacts of SARS-Cov2 positive patients in the health area of Cáceres.
Study Type
OBSERVATIONAL
Enrollment
3,000
To compare the results of the antigen detection test against the polymerase chain reaction in the study of contacts of COVID-19 patients during quarantine.
Sensitivity of the antigen detection test used in the study of contacts of COVID-19 patients.
The investigators will analyze the probability of a positive antigen detection test result in a COVID-19 patient contact with a positive polymerase chain reaction test.
Time frame: 2 days
Specificity of the antigen detection test used in the study of contacts of COVID-19 patients.
The investigators will analyze the probability of a negative antigen detection test result in a COVID-19 patient contact with a negative polymerase chain reaction test.
Time frame: 2 days
Positive predictive value of the antigen detection test used in the study of contacts of COVID-19 patients.
The investigators will analyze the probability that a subject considered COVID-19 patient contact with a positive antigen detection test result has a positive polymerase chain reaction test.
Time frame: 2 days
Negative predictive value of the antigen detection test used in the study of contacts of COVID-19 patients.
The investigators will analyze the probability that a subject considered COVID-19 patient contact with a negative antigen detection test result has a negative polymerase chain reaction test.
Time frame: 2 days
Positive likelihood ratio of the antigen detection test used in the study of contacts of COVID-19 patients.
The investigators will analyze how much the probability of having a positive polymerase chain reaction test increases when a subject considered a COVID-19 patient contact has a positive antigen detection test.
Time frame: 2 days
Negative likelihood ratio of the antigen detection test used in the study of contacts of COVID-19 patients.
The investigators will analyze how much the probability of having a positive polymerase chain reaction test decreases when a subject considered a COVID-19 patient contact has a negative antigen detection test.
Time frame: 2 days
Change in the pretest probability when the antigen detection test result is positive in a COVID-19 patient contact.
The investigators will analyze the change that occurs in the probability that a subject considered a COVID-19 contact has a positive polymerase chain reaction test before and after performing an antigen detection test with a positive result
Time frame: 2 days
Change in the pretest probability when the antigen detection test result is negative in a COVID-19 patient contact.
The investigators will analyze the change that occurs in the probability that a subject considered a COVID-19 contact has a positive polymerase chain reaction test before and after performing an antigen detection test with a negative result
Time frame: 2 days
Cut-off point of the cycle threshold of the polymerase chain reaction test that discriminates infectivity.
The investigators will analyze the cut-off point of polymerase chain reaction test (PCR) cycle threshold that maximizes discrimination of patients with at least one close contact with positive PCR (infectivity in the first circle of contacts).
Time frame: 2 weeks
Risk of SARS-CoV2 infection in close contacts of COVID-19 patients with a positive polymerase chain reaction test depending on whether the antigen detection test is positive or negative.
The investigators will compare the number of infected subjects by COVID-19 patient contacts with a positive polymerase chain reaction test, depending on whether the antigen detection test is positive or negative
Time frame: 2 weeks
To predict a positive result of the polymerase chain reaction test based on the appearance of symptoms during quarantine
Researchers will analyze the appearance of symptoms during quarantine in the contacts of COVID-19 patients and whether or not they have a positive polymerase chain reaction test.
Time frame: 10 days
The percentage of COVID-19 patient contacts with symptoms during the quarantine.
The investigators analyze the percentage of contacts of COVID-19 patients who develop symptoms during the quarantine.
Time frame: 10 days
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