Jaime Cerda L

Uso de tests diagnósticos en la práctica clínica (Parte 1): análisis de las propiedades de un test diagnóstico

Diagnostic tests are widely used in clinical practice. Qualitative analysis of diagnostic test properties (validity, reproducibility and safety) has been systematized using clinical epidemiology tools that have introduced a series of concepts such as sensitivity, specificity and predictive values. Based on data reported by a clinical investigation, the present article illustrates the theoretical background underlying these concepts, explains the methodology for their calculation, and analyzes their main strengths and limitations. A second article (Part 2: Clinical application and usefulness of a diagnostic test), describes the manner in which information provided by a test should be applied in order to correctly resolve a clinical dilemma.

Brotes de enfermedades transmitidas por alimentos y agua en la Región Metropolitana, Chile (2005-2010)

Antecedentes: Las enfermedades transmitidas por alimentos (ETA) constituyen en el ambito mundial, uno de los problemas sanitarios mas comunes y de mayor impacto sobre la salud de las personas. Objetivo: Analizar los brotes de ETA notificados en la Region Metropolitana (RM) de Chile entre enero 2005 y junio 2010. Material y Metodos: Estudio epidemiologico descriptivo de base de datos de brotes de ETA que se clasificaron de acuerdo a encuesta epidemiologica y muestra clinica o ambiental. Se analizaron variables de espacio, tiempo, lugar y persona. Resultados: De los 2.806 brotes notificados, 2.434 (86,7%) cumplieron con los criterios de inclusion. Un total de 12.196 personas fueron afectadas, con un promedio de 5 enfermos por brote. La tasa de incidencia del periodo 2005-2010 fue 32 casos por 100 habitantes Los ambitos de mayor brote fueron los hogares (36,2%), restaurantes (16,3%), supermercados (6,3%), ferias libres (4,4%). Los alimentos involucrados fueron mariscos (15,4%), pescados (15,1%), platos rapidos (13,5%). Los principales agentes etiologicos investigados fueron Salmonella spp, Shigella spp y Vibrio parahemolyticus. Conclusiones: Los brotes de ETA son muy frecuentes en la RM, comprometiendo un gran numero de personas. La mayoria se produjeron en los hogares y fueron provocados por mala manipulacion y/o conservacion de los alimentos.

Influencia del nivel socioeconómico (NSE) en el asma bronquial y cambios en su prevalencia en población escolar en un periodo de 6 años

Antecedentes: La prevalencia de asma se encuentra mundialmente en aumento, especialmente en paises en desarrollo. Objetivos: Determinar la prevalencia de asma en escolares de Santiago, estudiando la influencia del nivel socioeconomico (NSE) y describir su evolucion en un periodo de 6 anos. Material y metodos: Estudio transversal en poblacion escolar de la Region Metropolitana. Se encuesto a 4.561 escolares de 6-7 y 13-14 anos provenientes de establecimientos publicos de la comuna de Santiago y de colegios particulares pagados ubicados en el sector oriente de la ciudad. Las variables estudiadas fueron diagnostico de asma (DA), sibilancias en los ultimos 12 meses (SIB12) y frecuencia de episodios de sibilancias (FES). Mediante modelos de regresion se calcularon odds ratios para la ocurrencia de estas variables segun la exposicion a diversas variables independientes. Resultados: La prevalencia de DA en el grupo completo de escolares fue mayor en escolares varones respecto de mujeres (13,2% vs . 10,8%) (p = 0,016), siendo estadisticamente mayor en escolares de 13-14 anos respecto del grupo de 6-7 anos (13,8%: vs .10,1%). (p -4 ). Se encontro una asociacion inversa significativa entre NSE y SIB12. Un mayor nivel de educacion materna se asocio a menor prevalencia de SIB12 en ambos grupos de edad y de FES en ninos de 6-7 anos. Un mayor nivel de instruccion paterna determino un incremento en DA entre los mas pequenos. Incrementos significativos en la prevalencia de SIB12 y FES fueron observados entre 1994 y 2000 unicamente en escolares de 6-7 anos de Santiago Centro. Conclusion: Se encontro asociacion significativa entre NSE y el diagnostico y sintomatologia del asma en escolares de Santiago, asi como un incremento de su prevalencia y severidad en el grupo de 6-7 anos en el periodo 1994–2000.

Uso de tests diagnósticos en la práctica clínica (Parte 2): Aplicación clínica y utilidad de un test diagnóstico

The clinical usefulness of a diagnostic test is determined by the extent to which it helps to modify the pretest probability of occurrence of a certain diagnosis. For this purpose, the calculation and application of likelihood ratios (LR) is a very useful tool. Every possible result of a test has a LR, which allows for an estimation of the magnitude by which the pretest probability increases or decreases, thereby helping the physician rule out, confirm, or continue investigating a diagnosis with new tests. In the first part of this article the properties of a diagnostic test (validity, reproducibility and safety) were analyzed. This second part illustrates the theoretical background underlying the concept of LR, explains the methodology for calculating them and describes their clinical application.

Cambio climático y enfermedades infecciosas: Un nuevo escenario epidemiológico

For the international scientific community, it is undoubted that planetary temperature is increasing, being projected an average raise of 1.0 degrees C-3.5 degrees C by the year 2100. Forecasted consequences are diverse, most of them adverse for human health, including the establishment of favorable epidemiological scenarios for the emergence and reemergence of infectious diseases. The present article summarizes the available evidence regarding the mechanisms that promote climate change, its environmental effects and its consequences on human health. In order to accomplish this objective, demonstrated changes in the dynamics of zoonotic, vectorial, food and water-borne diseases are described. The position of Chile in the international community is commented, as well as multiple pending challenges, among which outstands the importance of incorporating professionals that work in the health sector to the national debate.

Fortalezas y debilidades del factor de impacto de revistas científicas

The impact factor is a bibliometric tool used to estimate the importance of scientific journals. It is calculated and published annually for journals indexed by the Institute for Scientific Information (ISI) and is a reflex of the average number of citations that each journal receives during a certain period of time. Since its creation it has been used as criteria in several decision-making processes such as buying journals subscriptions and submitting articles for publication. Operating under the hypothesis “the greater the impact factor, the greater the quality of a journal”, it has been subject of numerous controversies, especially due to certain biases around its calculation. The present article describes the Impact Factor and analyses the most important aspects in relation to its calculation, strengths, limitations and common errors on its application (Rev Med Chile 2007; 135: 1474-78). (Key words: Bibliometrics; Periodicals; Research support)

Introducción Precoz de Sustitutos de Lactancia Materna e Incidencia de Lactancia Materna Exclusiva al Mes de Vida

Breast Milk Substitutes at One Month of Life and Breastfeeding Suspension Risk Healthy term newborn feeding choice at the Maternity Ward may determine exclusive breastfeeding (EB) duration. Objective: Determine prospectively if early introduction of breast milk substitutes (BMS) or other liquids in healthy term newborns is associated to a reduction of EB incidence at 1 month of age. Methods: Concurrent cohort study of 211 healthy term neonates born in Hospital Clinico Universidad Catolica during October 2007-June 2007, 108 non-supplemented and 103 supplemented with milk formula or dextrose 5% du- ring the time they stayed at the Maternity Ward. Crude and adjusted risk of EB cessation between both groups was estimated at 1 month of age. Results: One month after birth, 40/100 (40.0%) of supplemented newborns and 26/101 (25.7%) non-supplemented newborns were not receiving exclusive breastfeeding (crude RR = 1.55 (CI95% 1.03-2.34)). Adjusted by maternal characteristics (age, education, breastfeeding experience, education in breastfeeding, EB time projection and paternal support) and newborn characteristics (type of delivery and birthweight), EB cessation risk was 55% higher in supplemented neonates (adjusted RR = 1.55, CI95% 1.01- 2.35). Conclusion: Early supplementation in healthy term newborns with BMS is associated to a higher risk of EB cessation at 1 month of age. (Key words: Breastfeeding, newborn, cessation). Rev Chil Pediatr 2010; 81 (4): 326-332

Mortalidad por cáncer infantil en Chile: Modelo de transición epidemiológica en la infancia

Pediatric cancer mortality in Chile. Model of epidemiological transition in infancy Background: The process of demographic and epidemiological transition that occurred in Chile during the second half of the 20 th century has been broadly described, with special emphasis in adults diseases. Objective: Characterize the process of epidemiological transition in infancy, using as model a disease that affects exclusively this age group (i.e. childhood cancer). Method: The trend of childhood cancer mortality rate and its proportion of deaths in relation to other diseases was analyzed for the period 1960-2000. Results: Childhood cancer mortality rate reduced 41.4% between 1960 and 2000 (5.8 to 3.4/100 000 children younger than 15-years old), mainly as a consequence of important advances in technology and public health organization. On the contrary, childhood cancer proportion of deaths increased 11-fold during the same period of time (4 to 43/1 000 children younger than 15 years-old), mainly as a consequence of reduction in transmittable diseases and malnutrition mortality rates. Conclusion: Knowing the characteristics of the epidemiological transition in infancy implies important changes and challenges for the Chilean pediatrician of the 21 st century, whose professional practice will be performed in a different scenario compared to the mid-20 th century.

Mortalidad por fibrosis quística en Chile (1997-2003)

Demographic and CF mortality data reported bythe National Institute of Statistics during the period 1997-2003 were recorded, according to sexand age. Overall mortality rate for each year was estimated, as well as the average mortalityrate during the same period in patients younger than 1 year, 1-4 years, 5-9 years, 10-14 yearsand older than 15 years.

Caracterización psicométrica, motora y funcional en niños con parálisis cerebral

Psychometric, motor and functional description in children with cerebral palsy Introduction: Cerebral Palsy (CP), the most frequent cause of chronic motor disability among children, is often associated to other alterations of cerebral function, among them cognitive function. International pu- blications show up to 70% of children with CP have normal intelligence (IQ). Objective: Determine IQ and motor function in a group of children with CP. Methodology: Prospective descriptive study of 34 children with CP, classifi ed according to type. Psychometric and motor tests were applied. Results: Of these children, 44% presented tetraparetic CP, 21% diparetic, 35% hemiparetic. Among tetraparetic children, 33% showed normal IQ, 14% mild Mental Retardation (MR), 53% severe MR. Among diparetic children, normal IQ, mild MR, severe MR showed in a frequency of 57%, 14% y 29% respectively. Children with hemiparesis showed normal IQ in 92% and mild MR in 8%. Motor function was usually proportional to IQ. Conclusion: In the full population studied, 59% of children showed normal IQ. Children with hemiparetic CP present better IQ, those with tetraparetic CP showed worst cognitive levels. Children with better IQ presented better motor function. (Key words: IQ, Disability, Motor Function, Cerebral Palsy, Neurorehabilitation, Psychometric Tests). Rev Chil Pediatr 2011; 82 (5): 388-394 RESUMEN