Antecedentes: Es necesario conocer la positividad de las pruebas COVID-19 para optimizar medidas epidemiológicas contra el COVID-19. Objetivo: Evaluar la proporción de pruebas moleculares positivas para SARS-COV-2 en adultos mexicanos con sospecha de COVID-19 del registro de vigilancia centinela. Métodos: Se recabaron datos abiertos de 1 969 006 pacientes con sospecha de COVID-19 del registro de abril-noviembre del 2020. El porcentaje de positividad se evaluó en tres grupos etarios (20-40, 40-60, >60 años) de acuerdo a la presencia o no de neumonía y al lugar de manejo del paciente; luego se efectuaron regresiones logísticas para evaluar factores asociados a la positividad al tercer día de síntomas. Resultados: Se observó que el 29.4% tuvo un RT-PCR positivo el día de inicio de síntomas y que el máximo porcentaje de positividad en el total de pacientes ocurrió al noveno día (56.6%). La edad (OR 1.08, 95% IC 1.07-1.09), sexo femenino (OR 0.93, 95% IC 0.92-0.93), ser contacto COVID-19 (OR 0.96, 95% IC 0.95-0.96) y tener un factor de riesgo (OR 0.96, 95% IC 0.96-0.97) se asociaron a la positividad al tercer día de enfermedad. Conclusiones: El primer día de síntomas sólo la tercera parte de sospechosos de COVID-19 tuvo una prueba molecular positiva. Se observó una mayor positividad de la prueba molecular a mayor tiempo de enfermedad y edad del paciente. La edad, ser de sexo femenino o contacto COVID-19 y tener un factor de riesgo se asociaron con tener una prueba positiva.
Background: It is necessary to know the positivity of COVID-19 tests to generate adequate public health measures. Objective: The objective is to evaluate the proportion of positive molecular tests for SARS-CoV-2 taken during April-November 2020 in Mexican adults with suspected COVID-19 infection according to the time of illness. Methods: Open data was collected from 1,969,006 patients with suspected COVID-19 infection from the April-November 2020 registry. The percentage of positivity was evaluated in three age groups (20-40, 40-60, >60 years) according to the presence or not of pneumonia and the place of patient management. Logistic regressions were performed to evaluate factors associated with positivity on the third day of symptoms. Results: The results showed that 29.4% had a positive RT-PCR on the first day of symptoms and that the highest percentage of positivity in all patients occurred on the ninth day (56.6%). Age (OR 1.08, 95% CI 1.07-1.09), female gender (OR 0.93, 95% CI 0.92-0.93), being a COVID-19 contact (OR 0.96, 95% CI 0.95-0.96), and having a risk factor (OR 0.96, 95% CI 0.96-0.97) were associated with positivity on the third day of illness. Conclusions: Less than a third of COVID-19 suspects had a positive molecular test on the first day of symptoms. We observed a higher positivity of the molecular test according to a longer time of disease and age of the patient. The age, being female, the presence of a COVID-19 contact, and having a risk factor was associated with a positive test.
