Frequency of cancer in children residing in Mexico City and treated in the hospitals of the Instituto Mexicano del Seguro Social (1996–2001)

BACKGROUND: The objective of this article is to present the frequency of cancer in Mexican children who were treated in the hospitals of the Instituto Mexicano del Seguro Social in Mexico City (IMSS-MC) in the period 1996–2001. METHODS: The Registry of Cancer in Children, started in 1996 in the IMSS-MC, is an on-going, prospective register. The data from 1996 through 2001 were analyzed and the different types of cancer were grouped according to the International Classification for Cancer in Children (ICCC). From this analysis, the general and specific frequencies by age and by sex were obtained for the different groups of neoplasms. Also, the frequency of the stage of the disease that had been diagnosed in cases of children with solid tumors was obtained. RESULTS: A total of 1,702 new cases of children with cancer were registered, with the male/female ratio at 1.1/1. Leukemias had the highest frequency with 784 cases (46.1%) and, of these, acute lymphoblastic leukemias were the most prevalent with 614 cases (78.3%). Thereafter, in descending order of frequency, were tumors of the central nervous system (CNST) with 197 cases (11.6%), lymphomas with 194 cases (11.4%), germinal cell tumors with 110 cases (6.5%), and bone tumors with 97 cases (5.7%). The highest frequency of cancer was found in the group of one to four year-olds that had 627 cases (36.8%). In all the age groups, leukemias were the most frequent. In the present work, the frequency of Hodgkin's disease (~4%) was found to be lower than that (~10%) in previous studies and the frequency of tumors of the sympathetic nervous system was low (2.3%). Of those cases of solid tumors for which the stage of the disease had been determined, 66.9% were diagnosed as being Stage III or IV. CONCLUSIONS: The principal cancers in the children treated in the IMSS-MC were leukemias, CNST, and lymphomas, consistent with those reported by developed countries. A 2.5-fold reduction in the frequency of Hodgkin's disease was found. Of the children, the stage of whose disease had been determined, two thirds were diagnosed as having advanced stages of the disease

Epidemiological and some clinical characteristics of neuroblastoma in Mexican children (1996–2005)

<p>Abstract</p> <p>Background</p> <p>Neuroblastoma (NB) is the principal tumor of the sympathetic nervous system in children under one year of age. The incidence in developed countries is greater than that in developing countries. The aim of this article is to present the epidemiological and some clinical characteristics of Mexican children with NB.</p> <p>Methods</p> <p>A population-based, prolective study, with data obtained from the Childhood Cancer Registry of the Instituto Mexicano de Seguro Social. Statistical analysis: The simple frequencies of the variables of the study and the annual average incidence (per 1,000,000 children/years) by age and sex were obtained. The trend was evaluated by calculating the annual percentage of change. The curves of Kaplan-Meyer were employed for the survival rate and the log-rank test was used to compare the curves.</p> <p>Results</p> <p>Of a total of 2,758 children with cancer registered during the period from 1996–2005, 72 (2.6%) were identified as having Group IV, defined according to the International Classification of Childhood Cancer. The incidence for NB was 3.8 per 1,000,000 children/year; NB was highest in the group of children under one year of age, followed by the group of children between the ages 1–4 years (18.5 and 5.4 per 1,000,000 children/years, respectively). The male/female ratio was 1.1 and there was no trend toward an increase. The time of diagnosis was 26 days (median), but varied according to the stage at diagnosis. Stages III and IV were presented in 88% of the cases. There was no association between the stage, the age at time of diagnosis, or the histological pattern. The overall five-year survival rate was 64%; the patients with stage I, II, III, or IVs did not die; and the five-year survival rate of cases in Stage IV was 40%.</p> <p>Conclusion</p> <p>It is possible that the low incidence of neuroblastoma in Mexican children is due to the difficulty in diagnosing the cases with the best prognosis, some of which could have had spontaneous regression. There was no trend to an increase; the majority of the cases were diagnosed in the advanced stages; and the overall five-years survival rate was similar to that for developed countries.</p

The research protocol V: The calculation of sample size

Sample size refers to the number of participants to be included in a research study. If the calculation is carried out properly, not only conclusions will be established with statistical support and the potential risks to the subjects included in the investigation will be limited, but also the study can be properly planned to optimize economic and time costs. Calculation of sample size requires information that must be supported by the research protocol. This information includes that the objectives (descriptive study or a study to establish differences between groups) and hypotheses are well elaborated (with magnitude and direction), the scale of measurement of the outcome variable(s) must be defined, and type I error and type II error appropriately identified. This review describes how to specify the requirements needed for sample size calculation, including examples in clinical research designs

Búsqueda y recuperación de la literatura científica

En sentido amplio, investigar involucra cualquier búsqueda y recopilación sistemática y pertinente de datos, información y hechos, así como su análisis, para aumentar el conocimiento sobre un tema determinado. Un aspecto fundamental durante el proceso de investigación involucra el conocimiento y dominio práctico de la literatura científica (alfabetización informacional). En este capítulo se presentan las principales bases de datos de la literatura académica que contienen datos relevantes a las áreas de la salud y biomédicas. Además, presentamos estrategias de búsqueda bibliográfica para facilitar su adquisición cotidiana, sistemática, reproducible y precisa, que nos permita realizar investigaciones profundas y generar nuevo conocimiento. Martínez-Ezquerro JD, Rendón-Macías ME (2021) “Búsqueda y recuperación de la literatura científica” en: (coord. Miguel Ángel Villasís-Keever, Mario Enrique Rendón-Macías) Guía práctica para la elaboración de protocolos de investigación clínica (24-39). Ciudad de México: Sociedad Mexicana de Pediatría, 250p. (ISBN 978-607-7545-07-1), doi: https://doi.org/10.31219/osf.io/y4ne

Clinical significance vs statistical significance. How to interpret the confidence interval at 95 %

The validity of a study depends on its proper planning, execution and analysis. If these are sufficiently correct, the decision to apply the recommendations issued depends on the expected clinical effect. This effect may have random variations, hence the need to use statistical inference. For years the p-value has been used to determine this statistical significance and the confidence intervals to measure the magnitude of the effect. In this review we present a proposal of how to interpret the 95 % confidence intervals (CI 95 %) as estimators of the expected effect variability based on considering the threshold or value of clinical significance and the null value of the difference or rejection of statistical significance. Thus, an association or effect where the CI 95 % includes the null value (no effect or difference) is interpreted as inconclusive; one between the null value and the clinical threshold (without including them) as possibly inconsequential; one that does not include the null value but the clinical threshold as yet not conclusive and one beyond the clinical threshold as conclusive

Alimentación con fórmula de inicio a libre demanda contra capacidad gástrica durante el periodo de transición

Introducción: La indicación del aporte por fórmula al recién nacido puede ser a libre demanda (LD) o por capacidad gástrica calculada (CGC). El objetivo de este trabajo fue determinar si la técnica de alimentación (LD vs. CGC) influye en el volumen ingerido, la tolerancia a la fórmula y el riesgo de hipoglucemia. Métodos: Se diseñó un ensayo clínico abierto no aleatorizado en neonatos a término, sanos, vigilados durante 24 h. Se determinó el volumen total ingerido (ml/kg), la tolerancia oral (vómitos-regurgitaciones, perímetro abdominal), la repercusión en el peso y datos de hipoglucemia. Resultados: Se analizaron en total 154 neonatos (CGC = 90 y LD = 64). Los neonatos en LD consumieron una mayor cantidad de fórmula (8 ml/kg; IC 95% 5-11) con mayor variación entre toma. No hubo diferencias en el porcentaje de pérdida ponderal (2.1% vs. 2%, p = 0.80). Los neonatos en LD mostraron más vómito (17.2% vs. 6.7%, p = 0.02) y mayor distención abdominal (43.8% vs. 22.2%, p = 0.007). Solo un neonato del grupo CGC mostró hipoglucemia (p = 1). Conclusiones: La alimentación por CGC permite una ingesta constante con menor riesgo de intolerancia, sin aumentar la posibilidad de hipoglucemia o pérdida de peso

Descriptive statistics

Descriptive statistics is the branch of statistics that gives recommendations on how to summarize clearly and simply research data in tables, figures, charts, or graphs. Before performing a descriptive analysis it is paramount to summarize its goal or goals, and to identify the measurement scales of the different variables recorded in the study. Tables or charts aim to provide timely information on the results of an investigation. The graphs show trends and can be histograms, pie charts, “box and whiskers” plots, line graphs, or scatter plots. Images serve as examples to reinforce concepts or facts. The choice of a chart, graph, or image must be based on the study objectives. Usually it is not recommended to use more than seven in an article, also depending on its length

Classical Hodgkin lymphoma histologic subtypes distribution among geographical regions and correlation with Human Development Index

Classical Hodgkin lymphoma (cHL) is classified into nodular sclerosis (NS), mixed cellularity (MC), lymphocyte rich (LR), and lymphocyte depleted (LD) histologic subtypes. Epidemiologic studies demonstrate remarkable diversity of subtype distribution among geographical regions and socioeconomic conditions. However, previous research has not examined the statistical correlation between subtypes’ proportion of cases among countries and socioeconomic factors, reported through a standardized parameter as the Human Development Index (HDI). Our aim was to analyze cHL histologic subtypes' frequency patterns among geographic regions and establish a correlation with countries' socioeconomic conditions.We conducted a systematic review in national registries, population-based reports and multicenter studies addressing histologic subtype frequency in different countries from 1980 to 2021. We evaluated 26,174 cHL patients from 27 countries among five geographic regions. For each cHL subtype, we calculated the Pearson correlation coefficient, determination coefficient and created scatter plots.North and Central America and Europe were the regions with the highest overall proportion of NS cases, while East and South Asia and Africa had the highest proportion of MC and LD cases. A significant positive correlation was confirmed between NS proportion of cases among countries and a higher HDI (R2=0.33, r = 0.57, p0.05 for LD). LR subtype distribution showed no correlation with HDI (R2 0.05).Early Epstein-Barr virus infection, host-related factors (as an altered immune response, nutritional status), human immunodeficiency virus infection, among other factors could explain these differences. Understanding cHL distribution patterns and their underlying causes, could allow to create public health interventions to improve social determinants of health in developing countries