Incidence moments: Short term forecast of the COVID-19 incidence rate in Chile

Introduction: The predictability of any epidemic is highly uncertain, especially regarding a new emerging pathogen such as SARS-CoV-2. Objectives: We studied the predictability of the incidence series of COVID-19 in Chile (whole country) and three regions with different population sizes. The analysis included the period intervened by vaccination campaigns and when new variants of the SARS-CoV-2 virus arrived. This study also is focused on possible differences in predictability between epidemic and "inter-epidemic" periods. Methods: We studied the daily incidence of COVID-19 in Chile for the Metropolitan, Biobío, Arica, and Parinacota regions from March 2020 to February 2022, with the recently proposed method of the third moment of incidence. We assessed the predictive capacity with the corrected mean arctangent absolute percent error. Results: The predictability of the daily incidence of COVID-19 was on the limit between good and reasonable for the entire epidemic process. The third moment of incidence produced reasonable predictions for regions with large population sizes and insufficient predictions for smaller regions. We found lower prediction capacity during the start of the pandemic and the epidemic caused by the Omicron variant. Conclusion: The third incidence moment method is suitable for short-term forecasting of COVID-19 with an error of around 30%. This forecast represents a short time of predictability in mainly chaotic dynamics. The predictability decreased only slightly due to pharmacological interventions and the income of new virus variants. We found low predictability in the initial periods of the epidemic and during the Omicron epidemic outbreak.

Introducción: La predictibilidad de cualquier epidemia es muy incierta, y más aún cuando se trata de un nuevo patógeno emergente como el SARS CoV-2. Objetivos: Estudiamos la predictibilidad de series de incidencia de COVID-19 en Chile y en tres regiones de distinto tamaño poblacional, incluyendo el período de intervención de las campañas de vacunación y llegada de variantes del virus SARS CoV-2. Estudiamos también las posibles diferencias en la predictibilidad entre los períodos epidémicos e "inter-epidémicos". Métodos: Se estudió la incidencia diaria de COVID-19 en Chile, para las regiones Metropolitana, Biobío y Arica y Parinacota de marzo de 2020 a febrero de 2022 con el método del tercer momento de incidencia propuesto recientemente. La capacidad de predicción se evaluó con el arcotangente del error porcentual absoluto medio corregido. Resultados: La predictibilidad de la incidencia diaria de COVID-19 estuvo en el límite entre buena y razonable durante todo el proceso epidémico. El tercer momento de incidencia produce predicciones razonables para regiones con gran tamaño de población y predicciones insuficientes para regiones más pequeñas. Se encontró menor capacidad de predicción durante el inicio de la pandemia y durante la epidemia provocada por la variante Omicron. Conclusión: El método del tercer momento de incidencia es un buen método para el pronóstico a corto plazo de COVID-19 que tiene un error de alrededor del 30%. Esto representa un tiempo corto de predictibilidad en una dinámica principalmente caótica. La predictibilidad disminuyó solo levemente debido a las intervenciones farmacológicas y al ingreso de nuevas variantes del virus. Se encontró baja predictibilidad en los períodos iniciales de la epidemia y en el brote epidémico de Omicron.

Factores de riesgo de ocurrencia y gravedad de malformaciones congénitas / Identification of risk factors for congenital malformations

Background: The relative importance of congenital malformations as a cause of death in the first year of life is increasing along with the control of preventable causes of perinatal mortality. Aim: To identify risk factors for congenital malformations. Patients and Methods: Retrospective case-control study of births registered in the database of The Latin American Collaborative Study of Congenital Malformations (ECLAMC), in the period 2001-2010. Results: Birth weight and gestational age were significantly lower in cases than controls, behaving as risk factors and associated with a greater severity of congenital malformations. The risk and severity of congenital malformations increased along with mother’s age. Fetal growth retardation, a history of congenital malformations in the family, physical factors and acute illnesses of the mother in the first trimester of pregnancy were also significant risk factors for congenital malformations and their severity. The educational level of the mother was a protective factor for congenital malformations and their severity. Conclusions: Variables previously identified as risk factors for congenital malformations, were significantly related with the occurrence of congenital malformations and their severity.

Valor de la secuencia de difusión en el estudio de cáncer de próstata en pacientes con antígeno prostático específico elevado / Value of diffusion-weighted sequences in the study of prostate cancer in patients with increased prostate specific antigen levels

En el carcinoma prostático la arquitectura glandular es reemplazada por células cancerosas, produciendo barreras al movimiento del agua, que pueden ser estudiadas con resonancia magnética potenciada en difusión. Para evaluar el aporte de estas secuencias en el estudio de la próstata, realizamos estudio descriptivo e inferencia!, utilizando difusión en 26 pacientes con tacto rectal anormal y antígeno prostático elevado. Se analizó sensibilidad, especificidad y curvas ROC basadas en coeficiente aparente de difusión (CAD). Se realizó biopsia prostática en 14 pacientes; 7 resultaron positivos. Con CAD <1000 um2/s, se encontraron altas sensibilidades con bajas especificidades y valores predictivos moderados. Incorporando T2 mejoraron: certeza diagnóstica, especificidad y valores predictivos. Al comparar los valores CAD en zonas con y sin cáncer, obtuvimos diferencias para CAD promedio y mínimo. Las curvas ROC mostraron áreas elevadas y significativas, sugiriéndose valores de corte de 1059 um2/s y 969 um2/s entre "normales" y con cáncer; LR(+) para valores de corte: 6,97 y 5,23 respectivamente. Nuestros resultados permiten proponer que se obtiene mayor ganancia diagnóstica en la interpretación conjunta de imágenes T2 y secuencias de difusión y que CAD permite diferenciar entre tejido normal y cáncer, por lo que se debiera incorporar en el estudio prostático.

In prostatic carcinoma, the glandular architecture is replaced by cancer cells producing barriers to water motion, anomaly that can be studied through diffusion-enhanced MRI technique. To assess the contribution of these sequences in the prostate cancer exploration, we conducted a descriptive and inferential study using diffusion-enhanced MRI technique in 26 patients with abnormal digital rectal examination (DRE) and increased prostate specific antigen (PSA) values. We analyzed sensitivity, specificity and ROC curves based on apparent diffusion coefficient (ADC). Seven out of 14 biopsies were positive in patients undergoing prostate biopsy. When applying ADC <1000 _m2/se, high sensitivity with low specificity levels, as well as moderate predictive values were obtained. By incorporating T2-weighted images, improved diagnostic accuracy, specificity and predictive values were achieved. When comparing ADC values in tissues with and without cancer, average and minimum ADC appeared to exhibit different values. ROC curves depicted increased and significant values, suggesting cutoff values of 1059 um2/s and 969/um2/s for healthy and malignant tissues, respectively; LR (+) for cut-off value: 6.97 and 5.23, respectively. Our results enable us to propose that improved diagnostic outcomes are attained through combined interpretation of T2-weighted images and diffusion-weighted sequences and that the ADC permits discrimination between normal and malignant tissues. Therefore, we strongly support that these criteria should be taken into account when performing prostate explorations.