Epidemiology of Melanoma in Spain: Estimation of Number of Patients With Stage III Disease Eligible for Adjuvant Therapies. / Epidemiología del melanoma en España: estimación de los pacientes con melanoma con estadio III candidatos al tratamiento adyuvante.

BACKGROUND AND OBJECTIVE: Accurate information on the incidence of melanoma by stage and a better understanding of transition between stages are important for determining the burden of disease and assessing the impact of new adjuvant therapies on recurrence and survival. The aim of this study was to estimate the incidence rates of the various stages of melanoma in Spain and to estimate the number of patients with stage III disease who are eligible for adjuvant systemic therapies. MATERIALS AND METHOD: We built an epidemiological model using prospectively collected data from patients diagnosed with de novo or recurrent melanoma between 2012 and 2016 in the melanoma units of 4 public hospitals. RESULTS: The estimated crude incidence rates for stage I and II melanoma were 7 and 2.9 cases per 100,000 person-years, respectively. The corresponding rates for stage III and IV melanoma were 1.9 and 1.3 cases per 100,000 person-years; 25.8% of patients with stage III melanoma were stage IIIA, 47% were stage IIIB, and 27.3% were stage IIIC. The respective estimated incidence rates for recurrent stage III and IV melanoma were 1.1 and 0.9 cases per 100,000 person-years. Overall, 54% of patients with recurrent stage III melanoma had progressed from stage I or II; the other cases corresponded to changes in substage. Of the patients with stage III melanoma, 85% of those with a de novo diagnosis and 80% of those who had relapsed had resectable disease, meaning they were eligible for adjuvant therapy; 47% of these patients had a BRAF mutation. CONCLUSIONS: The above estimates could have a major impact on health care resource planning. Assessing the number of patients with melanoma who are eligible for adjuvant therapies in melanoma could help decision-makers and clinicians anticipate future needs for the management of this disease.

Epidemiología del melanoma en España: estimación de los pacientes con melanoma con estadio III candidatos al tratamiento adyuvante / Epidemiology of Melanoma in Spain: Estimation of Number of Patients With Stage III Disease Eligible for Adjuvant Therapies

Antecedentes y objetivo: Para estimar la carga real del melanoma y el impacto de las nuevas terapias adyuvantes sobre las recaídas y la supervivencia, se precisa conocer con mayor exactitud la incidencia por estadios y analizar la transición entre ellos. Este estudio pretende estimar dicha incidencia y determinar el número de pacientes en estadio III que podrían beneficiarse del tratamiento sistémico adyuvante en España. Materiales y método: Se elaboró un modelo epidemiológico basado en datos de pacientes diagnosticados de melanoma o en recaída, recogidos prospectivamente durante 2012-2016 por cuatro unidades de melanoma de centros sanitarios públicos. Resultados: Las tasas brutas de incidencia estimadas para estadios I y II se situaron en 7 y 2,9 casos por 100.000 personas-año, respectivamente. Para estadio III se estimó en 1,9 (25,8% en IIIA, 47% en IIIB, y 27,3% en IIIC), siendo la de estadio IV de 1,3. La tasa de recaídas en estadio III se estimó en 1,1, siendo para estadio IV de 0,9. El 54% de recaídas a estadio III procedían de estadios I/II, mientras que el resto progresaban desde subestadios III. En estadio III, un 85% de nuevos diagnósticos y un 80% de recaídas fueron resecables, por tanto, candidatos a adyuvancia, de los cuales el 47% presentaba mutación en BRAF. Conclusiones: Estas estimaciones podrían tener un impacto importante en la planificación de los recursos sanitarios. La proyección en el número de potenciales candidatos a adyuvancia puede ayudar a decisores y clínicos a anticiparse a futuras necesidades en el manejo del melanoma (AU)

Background and objective: Accurate information on the incidence of melanoma by stage and a better understanding of transition between stages are important for determining the burden of disease and assessing the impact of new adjuvant therapies on recurrence and survival. The aim of this study was to estimate the incidence rates of the various stages of melanoma in Spain and to estimate the number of patients with stage III disease who are eligible for adjuvant systemic therapies. materials and method: We built an epidemiological model using prospectively collected data from patients diagnosed with de novo or recurrent melanoma between 2012 and 2016 in the melanoma units of 4 public hospitals. Results: The estimated crude incidence rates for stage I and II melanoma were 7 and 2.9 cases per 100,000 person-years, respectively. The corresponding rates for stage III and IV melanoma were 1.9 and 1.3 cases per 100,000 person-years; 25.8% of patients with stage III melanoma were stage IIIA, 47% were stage IIIB, and 27.3% were stage IIIC. The respective estimated incidence rates for recurrent stage III and IV melanoma were 1.1 and 0.9 cases per 100,000 person-years. Overall, 54% of patients with recurrent stage III melanoma had progressed from stage I or II; the other cases corresponded to changes in substage. Of the patients with stage III melanoma, 85% of those with a de novo diagnosis and 80% of those who had relapsed had resectable disease, meaning they were eligible for adjuvant therapy; 47% of these patients had a BRAF mutation. Conclusions: The above estimates could have a major impact on health care resource planning. Assessing the number of patients with melanoma who are eligible for adjuvant therapies in melanoma could help decision-makers and clinicians anticipate future needs for the management of this disease (AU)

[Translated article] Epidemiology of Melanoma in Spain: Estimation of Number of Patients With Stage III Disease Eligible for Adjuvant Therapies / Epidemiología del melanoma en España: estimación de los pacientes con melanoma con estadio III candidatos al tratamiento adyuvante

Background and objective: Accurate information on the incidence of melanoma by stage and a better understanding of transition between stages are important for determining the burden of disease and assessing the impact of new adjuvant therapies on recurrence and survival. The aim of this study was to estimate the incidence rates of the various stages of melanoma in Spain and to estimate the number of patients with stage III disease who are eligible for adjuvant systemic therapies. materials and method: We built an epidemiological model using prospectively collected data from patients diagnosed with de novo or recurrent melanoma between 2012 and 2016 in the melanoma units of 4 public hospitals. Results: The estimated crude incidence rates for stage I and II melanoma were 7 and 2.9 cases per 100,000 person-years, respectively. The corresponding rates for stage III and IV melanoma were 1.9 and 1.3 cases per 100,000 person-years; 25.8% of patients with stage III melanoma were stage IIIA, 47% were stage IIIB, and 27.3% were stage IIIC. The respective estimated incidence rates for recurrent stage III and IV melanoma were 1.1 and 0.9 cases per 100,000 person-years. Overall, 54% of patients with recurrent stage III melanoma had progressed from stage I or II; the other cases corresponded to changes in substage. Of the patients with stage III melanoma, 85% of those with a de novo diagnosis and 80% of those who had relapsed had resectable disease, meaning they were eligible for adjuvant therapy; 47% of these patients had a BRAF mutation. Conclusions: The above estimates could have a major impact on health care resource planning. Assessing the number of patients with melanoma who are eligible for adjuvant therapies in melanoma could help decision-makers and clinicians anticipate future needs for the management of this disease (AU)

Antecedentes y objetivo: Para estimar la carga real del melanoma y el impacto de las nuevas terapias adyuvantes sobre las recaídas y la supervivencia, se precisa conocer con mayor exactitud la incidencia por estadios y analizar la transición entre ellos. Este estudio pretende estimar dicha incidencia y determinar el número de pacientes en estadio III que podrían beneficiarse del tratamiento sistémico adyuvante en España. Materiales y método: Se elaboró un modelo epidemiológico basado en datos de pacientes diagnosticados de melanoma o en recaída, recogidos prospectivamente durante 2012-2016 por cuatro unidades de melanoma de centros sanitarios públicos. Resultados: Las tasas brutas de incidencia estimadas para estadios I y II se situaron en 7 y 2,9 casos por 100.000 personas-año, respectivamente. Para estadio III se estimó en 1,9 (25,8% en IIIA, 47% en IIIB, y 27,3% en IIIC), siendo la de estadio IV de 1,3. La tasa de recaídas en estadio III se estimó en 1,1, siendo para estadio IV de 0,9. El 54% de recaídas a estadio III procedían de estadios I/II, mientras que el resto progresaban desde subestadios III. En estadio III, un 85% de nuevos diagnósticos y un 80% de recaídas fueron resecables, por tanto, candidatos a adyuvancia, de los cuales el 47% presentaba mutación en BRAF. Conclusiones: Estas estimaciones podrían tener un impacto importante en la planificación de los recursos sanitarios. La proyección en el número de potenciales candidatos a adyuvancia puede ayudar a decisores y clínicos a anticiparse a futuras necesidades en el manejo del melanoma (AU)

Gene promoter hypermethylation is found in sentinel lymph nodes of breast cancer patients, in samples identified as positive by one-step nucleic acid amplification of cytokeratin 19 mRNA.

We analysed the promoter methylation status of five genes, involved in adhesion (EPB41L3, TSLC-1), apoptosis (RASSF1, RASSF2) or angiogenesis (TSP-1), in intraoperative sentinel lymph node (SLN) biopsy samples from patients with breast cancer, that had been processed by the one-step nucleic acid amplification (OSNA) technique. SLN resection is performed to estimate the risk of tumour cells in the clinically negative axilla, to avoid unnecessary axillary lymph node dissection. OSNA is currently one of the eligible molecular methods for detecting tumour cells in SLNs. It is based on the quantitative evaluation of cytokeratin 19 mRNA which allows distinguishing between macrometastasis, micrometastasis and isolated tumour cells, on the basis of the quantity of tumour cells present. There have been no prior studies on the question whether or not samples processed by OSNA can be used for further molecular studies, including epigenetic abnormalities which are some of the most important molecular alterations in breast cancer. Genomic DNA was extracted from samples obtained from 50 patients diagnosed with primary breast cancer. The content of tumour cells in SLNs was evaluated by OSNA, and the promoter methylation status of the selected genes was analysed by methylation-specific PCR. All were found to be hypermethylated to a variable degree, and RASSF1 hypermethylation was significantly associated with macrometastasis, micrometastasis and isolated tumour cells (p = 0.002). We show that samples used for OSNA are suitable for molecular studies, including gene promoter methylation. These samples provide a new source of material for the identification of additional biomarkers.

[Gastric carcinoma in patients younger than 30 years of age. Report of 11 cases]. / Carcinoma gástrico en pacientes menores de 30 años. Presentación de once casos.

Eleven cases of gastric carcinoma occurring in patients younger than 30 years were found in a pool of 929 diagnosed in Hospital General de Castelló during the period of 1976 to 1995. Ten patients were male (10/11). The mean age was 26.9 years. In eight cases precancerous lesions were present. The mean time between diagnosis and surgery was 9 months. The most frequent location was the antrum (63.6%) and the most common histology was gastric/diffuse adenocarcinoma of signet-ring cell type (45.5%). Amplified partial gastrectomy was performed in 81.8%, with Billroth II anastomosis in 36.4%. Immediate postoperative mortality rate was 9.1% and the overall mean survival 56 months, being of 54% and 36% at two and five years, respectively.

Systematic review and meta-analysis of vagus nerve stimulation in the treatment of depression: variable results based on study designs.

PURPOSE: To determine the efficacy of vagus nerve stimulation (VNS) for treatment of depression. METHODS: We conducted a systematic review and meta-analysis of analytical studies. Efficacy was evaluated according to severity of illness and percentage of responders. RESULTS: We identified 687 references. Of these, 14 met the selection criteria and were included in the review. The meta-analysis of efficacy for uncontrolled studies showed a significant reduction in scores at the Hamilton Depression Rating Scale endpoint, and the percentage of responders was 31.8% ([23.2% to 41.8%], P<0.001). However, the randomised control trial which covered a sample of 235 patients with depression, reported no statistically significant differences between the active intervention and placebo groups (OR=1.61 [95%CI 0.72 to 3.62]; P=0.25). To study the cause of this heterogeneity, a meta-regression was performed. The adjusted coefficient of determination (R2(Adj)) was 0.84, which implies that an 84% variation in effect size across the studies was explained by baseline severity of depression (P<0.0001). CONCLUSION: Currently, insufficient data are available to describe VNS as effective in the treatment of depression. In addition, it cannot be ruled out that the positive results observed in the uncontrolled studies might have been mainly due to a placebo effect.

Curso de introducción a la investigación clínica. Capítulo 9: Investigación secundaria: la revisión sistemática y el metaanálisis / Introduction course to clinical research. Chapter 9: Secondary research: systematic review and meta-analysis

La revisión sistemática y el metaanálisis forman parte de la investigación secundaria, la cual parte del estudio de las pruebas disponibles sobre una determinada intervención sanitaria, con el objeto de responder a cuestiones concretas, siguiendo una metodología explícita y rigurosa. El primer paso en su elaboración es la formulación de la pregunta de investigación, que definirá los criterios de inclusión de los estudios de nuestra revisión: metodología del estudio, participantes, intervenciones, comparaciones a estudiar y medidas de resultado. Estas características marcarán el protocolo de estudio y su correcta definición facilitará el resto del proceso. La siguiente etapa consiste en la búsqueda de estudios en la literatura científica sobre el tema a tratar, y la lectura crítica de los mismos para descartar ­en ocasiones simplemente con la lectura del título o el abstract y en otras revisando el artículo completo­ aquellos que no reúnen nuestros criterios de selección y quedarnos con los que finalmente serán incluidos. Estos estudios constituirán nuestra revisión, de ellos se extraerán los datos necesarios y se evaluarán tanto cualitativa como cuantitativamente. En aquellos casos en los que exista homogeneidad entre los estudios incluidos, y al menos dos de ellos presenten datos razonablemente combinables, se realizará un análisis cuantitativo denominado "metaanálisis", generalmente mediante la ayuda de programas estadísticos informatizados que facilitan este trabajo, y que permiten visualizar los resultados gráficamente en los denominados forest plot. La última fase de una revisión, al igual que en el resto de estudios epidemiológicos, consiste en interpretar los resultados obtenidos y extraer las correspondientes conclusiones, que en este tipo de estudios tendrán repercusiones tanto para la investigación, como para la práctica clínica

The systematic review and meta-analysis form a part of secondary research which begins with the study of the evidence available on a certain health care intervention in order to respond to specific questions by means of an explicit and rigorous methodology. The first step in its elaboration is the writing of the research question that will define the inclusion criteria of the studies of our review: study methodology, participants, interventions, comparisons to be studied and measurements of the results. These characteristics will define the study protocol and their correct definition will facilitate the rest of the procedure. The following stage consists in the search for studies in the scientific literature on the subject in question and the critical reading of them to rule out, sometimes only by reading the title or abstract and others by reading the complete article, those that do not fulfill our selection criteria. Finally, those remaining will be included in the study. These studies will make up our review and will be used to obtain the necessary data and to evaluate them both qualitatively and quantitatively. In those cases where there is homogeneity between the studies included and where at least two of them have reasonably combinable data, a quantitative analysis called meta-analysis will be conducted. This is generally done with the help of computerized statistical programs that aid this work and that make it possible to visualize the results graphically in the so-called forest plot. The last phase of the review, as in the rest of the epidemiological studies, consists in interpreting the results obtained and in drawing the corresponding conclusions. In this type of studies, they will have repercussions in both the research and clinical practice

Capítulo 1: Formulación de la pregunta de investigación / Chapter 1: Formulating the research question

La investigación clínica o aplicada, es un proceso cuyo objetivo es resolver cuestiones planteadas en cada una de las etapas del proceso asistencial para poder mejorar tanto la práctica clínica diaria, como la calidad de la atención prestada a los pacientes. El punto de partida de todo proceso de investigación es el planteamiento de una incertidumbre, que toma forma mediante la formulación de una pregunta de investigación. Ésta permitirá el desarrollo de una estrategia científica y un protocolo de trabajo que nos conducirán a resolver nuestra incertidumbre inicial. Las cuestiones suelen surgir en tres escenarios principales: para sustituir o mejorar actuaciones o intervenciones de la práctica asistencial diaria, ante la existencia de lagunas de conocimiento, o en el campo de la docencia. Para formular una pregunta correctamente es necesario que reúna una serie de características en cuanto a estructura y a contenido; debe estar correctamente operativizada, de tal modo que en su estructura ha de contener la información necesaria que permita definir y diferenciar el tipo de pacientes y/ o patología a estudiar, la intervención que vamos a realizar, si se trata de un estudio de intervención y las medidas de resultado que deseamos conocer. Para la obtención de resultados útiles es deseable, además, reunir las características de factibilidad, interés, novedad y relevancia. Una pregunta bien formulada ayudará al desarrollo de otras etapas del proceso de investigación, y además, facilitará la obtención de resultados ajustados a nuestra cuestión inicial y el posterior manejo de éstos, tanto para la realización de investigaciones secundarias, como para satisfacer adecuadamente las necesidades individuales de conocimiento

Clinical or applied research is a procedure whose objective is to resolve questions established on each one of the stages of the care procedure to be able to improve both the daily clinical practice and quality of care given to the patients. The starting point of all research procedures is the statement of an uncertainty that is formed by formulating a research question. This allows for the development of a scientific strategy and work protocol that will lead us to solve our initial uncertainty. The questions generally arise on three main scenarios: to substitute or improve actions or interventions of the daily care practice when there are knowledge gaps or in the teaching field. To formulate a question correctly, a series of characteristics on structure and content must be gathered. The question should be correctly made operative so that its structure should contain the information necessary to make it possible to define and differentiate the type of patients and/or disease to be studied, the intervention that we are going to conduct if this is an intervention study and the measurements of the outcome that we want to know. To obtain useful results it is also desirable to gather the characteristics of feasibility, interest, novelty and relevance. A well-formulated question will help to develop other research procedure stages and will also facilitate the obtaining of results adapted to our initial question and the subsequent management of these results for both the conduction of secondary investigations and to adequately satisfy the individuals needs of knowledge

Curso de introducción a la Investigación Clínica. Capítulo 3: La investigación a partir de la observación. Estudios descriptivos. Estudios analíticos / Introduction course to Clinical Research. Chapter 3: Research based on observation. Descriptive studies. Analytic studies

El diseño de un estudio consiste en un conjunto de procedimientos, métodos y técnicas mediante las cuales el investigador selecciona la variable respuesta, define los criterios de selección de la población en estudio, calcula el número de sujetos necesarios en la(s) muestra(s) y selecciona las variables que deben medirse, con el objetivo de estimar la magnitud del efecto o de la respuesta observada, controlar los factores de confusión e interpretar los resultados. La elección del tipo de diseño dependerá fundamentalmente del objetivo del estudio, de las hipótesis planteadas y de los recursos de los que disponga el grupo de investigación. Los estudios descriptivos permiten analizar cómo son y cómo se manifiestan los fenómenos de salud y permiten al investigador detallar las características más importantes de la enfermedad o del evento en estudio. Por el contrario, los estudios analíticos pretenden encontrar las causas que ocasionan esos fenómenos y estudian la relación entre diferentes variables, generalmente entre una causa y un efecto

The design of the study consists in a combination of procedures, methods and techniques by which the investigator selects the response variable, defines study population selection criteria, calculates the number of subjects needed in this sample(s) and selects the variables that should be measured in order to estimate the magnitude of the effect or of the response observed, to control confounding factors and interpret the results. The choice of the type of design will basically depend on the study objectives, and the hypotheses proposed and on the resources that the research group has. Descriptive studies make it possible to analyze how the health phenomena are manifested and what they are and make it possible for the investigator to detail the most important characteristics of the disease or event under study. On the contrary, analytic studies aim to find the causes of these phenomena and studied the relationship between different variables, generally between a cause and effect

Curso de introducción a la investigación clínica. Capítulo 4: El ensayo clínico. Metodología de calidad y bioética / Introduction course to clinical research. Chapter 4: The clinical trial. Quality and bioethical methodology

Los estudios analíticos permiten estudiar y verificar hipótesis causales, y los ensayos clínicos, en particular, aportan el mayor nivel de evidencia en la comprobación de estas hipótesis. Un ensayo clínico aleatorio (ECA) es un experimento planificado en el que, de forma prospectiva, se comparan dos o más intervenciones preventivas, curativas o rehabilitadoras, que son asignadas de forma individualizada y aleatoria a un grupo de pacientes para estudiar el efecto de estas intervenciones en el hombre. Para su realización es necesario tener en cuenta una serie de aspectos metodológicos, como la elección de la muestra de sujetos a partir de unos adecuados criterios de selección, asignación aleatoria de los sujetos a los diferentes grupos de intervención, elección del grupo control, enmascaramiento o cegamiento de algunos o todos los sujetos que intervienen en el estudio, y descripción de pérdidas y abandonos para un correcto análisis de los datos. Las características de este tipo de estudios, realizados sobre humanos, implican la necesidad del cumplimiento de unos requisitos éticos y legales que protejan a los participantes, motivo por el cual es imprescindible la obtención de un consentimiento informado, así como el informe favorable de un Comité Ético de Investigación Clínica para su realización

Analytic studies make it possible to study and verify causal hypotheses and clinical studies, specifically contribute the greatest level of evidence in the verification of these hypothesis. A randomized clinical trial (RCT) is a planned experiment in which two or more preventive, curative or rehabilitating interventions, assigned in an individualized and random way to a group of patients to study the effect of these interventions in man, are compared. To do so, a series of methodological aspects must be taken into account, such as the choice of the subject sample based on adequate screening criteria, random allotment of the subjects to the different intervention groups, choice of the control group, masking or blinding of some or all the subjects participating in the study and description of losses and drop-outs for correct analysis of the data. The characteristics of the type of study, conducted in humans, imply the need for the fulfillment of some ethical and legal requirements that protect the participants, reason why it is essential to obtain an informed consent and favorable report from the Ethics Committee for its conduction

Curso de introducción a la investigación clínica. Capítulo 5: Selección de la muestra: técnicas de muestreo y tamaño muestral / Introduction course to clinical research. Chapter 5: Sample selection: sampling techniques and sample size

Para realizar un proyecto de investigación debemos obtener datos de la población objetivo, que se define como el conjunto de elementos del cual se quiere conocer cierto aspecto. En algunos estudios cada elemento de la población puede ser medido realmente, lo cual es posible solamente si la población no es muy numerosa y si todos los elementos son accesibles. Pero lo habitual es que el estudio completo de la población sea inviable, ya que el trabajo empírico necesario es costoso e implica mucho tiempo y recursos. Para obtener resultados confiables no es necesario obtener los datos de todos los elementos poblacionales, es suficiente recoger las variables de un subconjunto de elementos denominado muestra. El estudio tendrá la validez y la fiabilidad necesarias si este subconjunto es representativo de la población objetivo y los resultados obtenidos son extrapolables a la misma. Existen distintas técnicas o procedimientos para seleccionar la muestra, dependiendo del tiempo, de los recursos económicos y de la naturaleza de los elementos poblacionales. El conjunto de estas técnicas se denomina muestreo. En el diseño del estudio se debe definir el tamaño muestral necesario; su cálculo está relacionado con ciertos problemas que estudia la Inferencia Estadística y que permitirán extraer conclusiones científicamente válidas a la población

To carry out a research project it is necessary to obtain data from the target population, which is defined as the set of elements about which we aim to find out a certain aspect. In some studies, this aspect can be directly measured in each element of the population; however, this is only possible if the population is not very large and if all of the elements are accessible. In the vast majority of cases, it is not viable to study the entire population because the empirical work necessary is expensive and involves much time and resources. To obtain reliable results, it is not necessary to obtain all of the data from all of the elements of the population; it is sufficient to collect the variables in a subgroup of elements called the sample. Unless this subgroup is representative of the target population, the results of the study cannot be extrapolated and will not be valid or reliable for the target population as a whole. There are different techniques or procedures to select the sample, depending on the time and financial resources available, as well as the nature of the elements of the population. This set of techniques is called sampling. When designing a study, it is necessary to define the necessary sample size, which involves certain problems studied by Inferential Statistics and will enable scientifically valid conclusions to be reached regarding the population

Curso de introducción a la investigación clínica. Capítulo 7: Estadística: Estadística Descriptiva y Estadística Inferencial / Introduction course to clinical research. Chapter 7: Statistics: descriptive and inferential statistics

La estadística estudia los métodos científicos para recoger, organizar, resumir y analizar datos, permite obtener conclusiones válidas y tomar decisiones razonables basadas en el análisis. La estadística es, por tanto, la ciencia que recoge, clasifica y analiza la información que se presenta habitualmente mediante datos agregados que permiten que las observaciones puedan cuantificarse, medirse, estimarse y compararse utilizando medidas de tendencia central, medidas de distribución, métodos gráficos, etc. La estadística aplicada trata sobre cómo y cuándo utilizar los procedimientos matemáticos (estadística matemática) y cómo interpretar los resultados que se obtienen. Así, la bioestadística es la rama de la estadística que enseña y ayuda a investigar en todas las áreas de las ciencias de la vida donde la variabilidad es la regla. Se divide en dos grandes ramas, la bioestadística descriptiva y la bioestadística analítica o inferencial. La estadística descriptiva resume la información contenida en los datos recogidos y la estadística inferencial demuestra asociaciones y permite hacer comparaciones entre características observadas

Statistics is the study of the scientific methods for collecting, organizing, summarizing, and analyzing data; it makes it possible to reach valid conclusions and make reasonable decisions on the basis of the analysis. Statistics is, therefore, the science of gathering, classifying, and analyzing information that is usually presented through aggregated data that enable observations to be quantified, measured, estimated, and compared using measurements of central tendency, measurements of distribution, graphical methods... Applied statistics deals with how and when to use the mathematical procedures (mathematical statistics) and how to interpret the results that are obtained using these procedures. Likewise, biostatistics is the branch of statistics that teaches and helps the investigator to carry out research in all of the different branches of the life sciences where variability is the rule. Biostatistics can be divided into two main areas: descriptive biostatistics and analytical or inferential statistics. Descriptive statistics summarizes the information contained in the data collected and inferential statistics demonstrates associations and makes it possible to make comparisons among the characteristics observed