COVID-19 Contact Study by Antigen Detection Test

Study Overview
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Brief Summary
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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.

Official Title
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Diagnostic Efficacy of the SARS-CoV2 Antigen Detection Test for the COVID-19 Contact Study

Conditions
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SARS-CoV Infection

Intervention / Treatment
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* Diagnostic Test: Antigen detection test


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Subjects considered close contacts of COVID-19 patients according to the definition of the Ministry of Health of Spain at the time of inclusion. Exclusion Criteria: Subjects who do not obtain their informed consent for the study. Symptomatic subject at the time of inclusion.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| SARS-CoV2 contacts<br>Subjects considered close contacts of COVID-19 patients according to the definition of the Ministry of Health in the health area of Cáceres. | Diagnostic Test: Antigen detection test<br>* 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.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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. | 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. | 2 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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. | 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. | 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. | 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. | 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 | 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 | 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). | 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 | 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. | 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. | 10 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Antigen detection tests, Diagnostic efficacy, Contact study, Asymptomatic contacts