ABSTRACT
Resumen El objetivo fue describir los resultados de la implementación de una estrategia de vigilancia con el uso de test rápidos de detección de antígeno de SARS-CoV-2. Se realizó un estudio de cohorte retrospectiva entre diciembre de 2020 y marzo de 2021, que incluyó casos sospechosos de COVID-19 evaluados en un hospital público mediante test rápidos y, en los negativos, por test moleculares. Se realizó seguimiento telefónico de los casos positivos y sus contactos estrechos. Se estimaron indicadores de implementación y de transmisibilidad viral (probabilidad de generar transmisión, cantidad de contagios secundarios generados, tasa de ataque secundaria e índice de sobredispersión). Se analizó su asociación con el resultado del test diag nóstico por modelos multivariados. De 1706 pacientes analizados con test rápidos de detección de antígeno, 526 resultaron positivos y 1180 negativos (65 fueron positivos por test moleculares). Se contactaron 579 casos confirmados e identificaron 1669 contactos estrechos (85% con seguimiento completo); 398 contactos fueron positivos durante su cuarentena (tasa de ataque secundaria de 27.9%). De los 579 casos, 205 (35%) reportaron contagios sintomáticos, con un promedio de 0.91 casos secundarios por infector. Se observó sobredispersión de la transmisión. Los positivos confirmados por test rápido tuvieron mayores chances de generar casos secun darios, más casos secundarios por infector y mayor tasa de ataque que los confirmados por test molecular. En conclusión, la estrategia con test rápido de detección de antígeno tuvo una aceptabilidad y cobertura elevada y aceleró el diagnóstico e identificación de los individuos con mayor contagiosidad.
Abstract The objective was to describe the results of a surveillance strategy based on the use of SARS-CoV-2 rapid antigen de tection tests. A retrospective cohort study was held between December 2020 and March 2021, which included suspected cases of COVID-19 evaluated by rapid antigen tests at a public hospital, with confirmatory molecular tests in negative cases. Positive cases and their close contacts were followed up by telephone. The scope, ac ceptability, follow-up coverage and positivity rate of the strategy were estimated, as well as indicators of viral transmissibility (probability of generating transmission, number of secondary infections generated, secondary attack rate, and overdispersion index). Its association with diagnostic tests results was analyzed by multivariate models. Of 1706 patients tested by rapid antigen tests, 526 were positive and 1180 were negative (65 tested positive by molecular tests); 579 confirmed cases could be contacted and 1669 close contacts were identified (85% of these contacts had full follow-up); 398 contacts tested positive during their quarantine (secondary attack rate of 27.9%). Of the 579 contacted cases, 205 (35%) reported symptomatic transmission, with an average of 0.91 secondary cases per infector. Transmission overdispersion was observed. Positive cases confirmed by rapid antigen tests had a higher chance of generating secondary cases, a higher number of secondary cases per infector and a higher secondary attack rate than those confirmed by molecular tests. In conclusion, the rapid antigen tests strategy showed high acceptability and coverage, and accelerated the diagnosis and identification of individuals with the highest contagiousness.
ABSTRACT
Background:Accurate diagnosis and widespread use of diagnostic tests with easy accessis important to contain the spread of SARS-CoV-2. A Real-time reverse transcription polymerase chain reaction (RT-PCR) has high cost and can be performed in special laboratories. There have been several easy to perform rapid antigen detection tests developed and recommended to use at point of care for timely detection of positive patients and their isolation to limit the spread of infection. The aim of the study was to compare the cost effectiveness and the role of RT-PCR and rapid antigen testing in diagnosing different suspects of COVID-19.Methods:In this cross-sectional study the data of all the suspected cases who underwent COVID-19 testing over a period of seven weeks at divisional level was used for analysis.Results:The widespread use of rapid antigen testing makes it more cost effective in detecting COVID-19 cases than the highly sensitive and specific RT-PCR testing. Conclusions:Rapid antigen tests can be used as a screening testing tool in high-risk groups to identify the infected persons quickly and for preventing the transmission of infection particularly in low resource settings.
ABSTRACT
@#<p><strong>BACKGROUND:</strong> Improving the means to detect SARS-COV-2 infection is important in the ongoing battle against the COVID-19 pandemic. STANDARDTM Q COVID-19 Ag Test offers an easy to use, cheap and rapid way of testing that must be evaluated first to optimize its utility.</p><p><strong>OBJECTIVES: </strong>This study aims to evaluate the diagnostic accuracy of this test kit compared with Reverse Transcription Polymerase Chain Reaction (RT-PCR) for SARS-COV-2 diagnosis.</p><p><strong>METHODS</strong>: Using retrospective cross-sectional study, seventy seven (77) nasopharyngeal swabs in viral transport media were used to determine the sensitivity, specificity, positive predictive value and negative predictive value of STANDARDTM Q COVID-19 Ag Test compared with the reference method, RT-PCR.</p><p><strong>RESULTS: </strong>Among all participants, the rapid antigen test has a sensitivity of 9.86%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 8.57%. The sensitivity increases among symptomatic participants and when Ct value is less than 20 to 25.00% and 31.58%, respectively.</p><p><strong>CONCLUSION: </strong>Despite the low sensitivity, STANDARDTM Q COVID-19 Ag Test has a high specificity and positive predictive value and could be a cheap and efficient test in the proper clinical context. Its use in conjunction with RT-PCR for those who tested negative initially should be emphasized in the implementation of the existing policies.</p>