El valor de p del test no es un ‘índice matemático’, es simplemente una frecuencia relativa / The p-value of the test is not a ‘mathematical index’, it is simply a relative frequency

Las revistas científicas más importantes en campos como medicina, biología y sociología publican reiteradamente artículos y editoriales denunciando que un gran porcentaje de médicos no entiende los conceptos básicos del análisis estadístico, lo que favorece el riesgo de cometer errores al interpretar los datos, los hace más vulnerables frente a informaciones falsas y reduce la eficacia de la investigación. Este problema se extiende a lo largo de toda su carrera profesional y se debe, en gran parte, a una enseñanza deficiente en estadística que es común en países desarrollados. En palabras de H. Halle y S. Krauss, ‘el 90% de los profesores universitarios alemanes que usan con asiduidad el valor de p de los test no entiende lo que mide ese valor’. Es importante destacar que los razonamientos básicos del análisis estadístico son similares a los que realizamos en nuestra vida cotidiana y que comprender los conceptos básicos del análisis estadístico no requiere conocimiento matemático alguno. En contra de lo que muchos investigadores creen, el valor de p del test no es un ‘índice matemático’ que nos permita concluir claramente si, por ejemplo, un fármaco es más efectivo que el placebo. El valor de p del test es simplemente un porcentaje.(AU)

Abstract. Leading scientific journals in fields such as medicine, biology and sociology repeatedly publish articles and editorials claiming that a large percentage of doctors do not understand the basics of statistical analysis, which increases the risk of errors in interpreting data, makes them more vulnerable to misinformation and reduces the effectiveness of research. This problem extends throughout their careers and is largely due to the poor training they receive in statistics – a problem that is common in developed countries. As stated by H. Halle and S. Krauss, ‘90% of German university lecturers who regularly use the p-value in tests do not understand what that value actually measures’. It is important to note that the basic reasoning of statistical analysis is similar to what we do in our daily lives and that understanding the basic concepts of statistical analysis does not require any knowledge of mathematics. Contrary to what many researchers believe, the p-value of the test is not a ‘mathematical index’ that allows us to clearly conclude whether, for example, a drug is more effective than a placebo. The p-value of the test is simply a percentage.(AU)

Adsorption of Ciprofloxacin on Clay Minerals in Argentinian Santa Rosa-Corrientes Soils.

The presence of antibiotics in soils is increasing drastically in last decades due to the intensive farming industry and excessive human consumption. Clay minerals are one of the soil components with great adsorption capacity for organic pollutants. The study of interactions between antibiotics and mineral surfaces will give us scientific knowledge of these pollutants through soils. In this work, we study the adsorption of the antibiotic ciprofloxacin in the clay mineral fraction of soils from the Argentinian zone of Santa Rosa (Corrientes), in a collaborative research of experiments and atomistic modelling calculations of the intercalation of ciprofloxacin in the interlayer space of montmorillonite. Adsorption and desorption isotherms were performed and compared with different isotherm models. Additionally, enthalpy, entropy, and free energy were determined from equilibrium constants at a function of temperature. All these experiments and calculations lead to the conclusions that two adsorption types of ciprofloxacin are found on clay minerals: one weakly sorbed that is released during the desorption experiments, and other one strongly joined that remains in the soil.

Photocatalytic activity enhancement of two-step and one-pot synthesis of Pd/ZnO nanocomposites: an experimental and DFT study.

Pd/ZnO nanocomposites were successfully synthesized by means of one and two pot synthesis and applied in the photodegradation of Rh6G. The nanocomposites were characterized by XRD, SEM, TEM, FTIR and micro-Raman spectroscopies. It was found the presence of PdZn2, PdO and agglomerated particles in the support surface for the Palladium-based nanocomposites fabricated by one-pot route; the two-step method allowed the formation of spherical Pd nanoparticles, with homogeneous distribution in the nanocomposite matrix, with an average size of 2.16 nm. The results show higher photocatalytic efficiency for the samples fabricated under the two-step approach compared to the one-pot synthesis. Based on experimental results, density functional theory (DFT) calculations were carried out to understand the enhancement photocatalytic of Pd/ZnO nanocomposites. To achieve it, the ZnO (001) and (101) surfaces were built and decorated by different Pd coverages. The theoretical results indicated two different photocatalytic mechanisms. In ZnO (001) case, the electrons flowed from surface to Pd, generating the superoxide radical anion (⋅O2-). Furthermore, the density of states of the ZnO (001) surface was modified by impurity Pd-d states at proximity to the conduction states, which may work as electron acceptors states. On the other hand, we found that the electrons flow from Pd to ZnO (101) surface, inducing the formation of ⋅OH and ⋅O2- for the degradation of Rh6G. The density of states of the ZnO (101) revealed a reduction in its bandgap, due to Pd-d states localized above valence states. Hence, our theoretical results suggest that the Pd-d states may facilitate the mobility of electrons and holes in (001) and (101) surfaces, respectively, reducing the rate of charge recombination.

[The p-value of the test is not a 'mathematical index', it is simply a relative frequency]. / El valor de p del test no es un 'índice matemático', es simplemente una frecuencia relativa.

Leading scientific journals in fields such as medicine, biology and sociology repeatedly publish articles and editorials claiming that a large percentage of doctors do not understand the basics of statistical analysis, which increases the risk of errors in interpreting data, makes them more vulnerable to misinformation and reduces the effectiveness of research. This problem extends throughout their careers and is largely due to the poor training they receive in statistics - a problem that is common in developed countries. As stated by H. Halle and S. Krauss, '90% of German university lecturers who regularly use the p-value in tests do not understand what that value actually measures'. It is important to note that the basic reasoning of statistical analysis is similar to what we do in our daily lives and that understanding the basic concepts of statistical analysis does not require any knowledge of mathematics. Contrary to what many researchers believe, the p-value of the test is not a 'mathematical index' that allows us to clearly conclude whether, for example, a drug is more effective than a placebo. The p-value of the test is simply a percentage.

TITLE: El valor de p del test no es un 'índice matemático', es simplemente una frecuencia relativa.Las revistas científicas más importantes en campos como medicina, biología y sociología publican reiteradamente artículos y editoriales denunciando que un gran porcentaje de médicos no entiende los conceptos básicos del análisis estadístico, lo que favorece el riesgo de cometer errores al interpretar los datos, los hace más vulnerables frente a informaciones falsas y reduce la eficacia de la investigación. Este problema se extiende a lo largo de toda su carrera profesional y se debe, en gran parte, a una enseñanza deficiente en estadística que es común en países desarrollados. En palabras de H. Halle y S. Krauss, 'el 90% de los profesores universitarios alemanes que usan con asiduidad el valor de p de los test no entiende lo que mide ese valor'. Es importante destacar que los razonamientos básicos del análisis estadístico son similares a los que realizamos en nuestra vida cotidiana y que comprender los conceptos básicos del análisis estadístico no requiere conocimiento matemático alguno. En contra de lo que muchos investigadores creen, el valor de p del test no es un 'índice matemático' que nos permita concluir claramente si, por ejemplo, un fármaco es más efectivo que el placebo. El valor de p del test es simplemente un porcentaje.

Validation, Deployment, and Real-World Implementation of a Modular Toolbox for Alzheimer's Disease Detection and Dementia Risk Reduction: The AD-RIDDLE Project.

The Real-World Implementation, Deployment, and Validation of Early Detection Tools and Lifestyle Enhancement (AD-RIDDLE) project, recently launched with the support of the EU Innovative Health Initiative (IHI) public-private partnership and UK Research and Innovation (UKRI), aims to develop, test, and deploy a modular toolbox platform that can reduce existing barriers to the timely detection, and therapeutic approaches in Alzheimer's disease (AD), thus accelerating AD innovation. By focusing on health system and health worker practices, AD-RIDDLE seeks to improve and smooth AD management at and between each key step of the clinical pathway and across the disease continuum, from at-risk asymptomatic stages to early symptomatic ones. This includes innovation and improvement in AD awareness, risk reduction and prevention, detection, diagnosis, and intervention. The 24 partners in the AD-RIDDLE interdisciplinary consortium will develop and test the AD-RIDDLE toolbox platform and its components individually and in combination in six European countries. Expected results from this cross-sectoral research collaboration include tools for earlier detection and accurate diagnosis; validated, novel digital cognitive and blood-based biomarkers; and improved access to individualized preventative interventions (including multimodal interventions and symptomatic/disease-modifying therapies) across diverse populations, within the framework of precision medicine. Overall, AD-RIDDLE toolbox platform will advance management of AD, improving outcomes for patients and their families, and reducing costs.

Elaboración de una escala de puntuación predictiva de infección periamigdalina basada en signos y síntomas / Design of a predictive score table for peritonsillar infection based on signs and symptoms

Introducción La infección periamigdalina (IPA) supone un motivo de consulta urgente entre las molestias de garganta. Un diagnóstico diferido o incorrecto puede comprometer la vía aerodigestiva alta y resultar mortal en su evolución. Nuestro objetivo fue desarrollar un modelo predictivo de presencia de IPA que ayude en su rápida detección. Pacientes y métodos Un estudio observacional retrospectivo de 66 meses desde 2017 fue desarrollado en un hospital comarcal y su centro terciario de referencia, recogiendo datos de todos los pacientes diagnosticados de IPA y un volumen proporcional de sujetos con sintomatología faríngea sin IPA. Recopilación de datos clínicos, exploratorios y demográficos entre participantes. Su mayor riesgo relativo de presencia de IPA los etiquetó como variables a testar. Elaboración de una escala de puntuación de probabilidad de padecerla y análisis de regresión logística, con obtención de la curva ROC que ofreciera mejor correlación diagnóstica. Validación interna y cálculo de los valores predictivos de este modelo. Resultados Sobre 348 casos de IPA, la escala de valoración puntuó la presencia de 6 variables: trismus (3), disfagia-odinofagia unilateral (2), abombamiento velar (2), otalgia refleja (1), faringolalia (1) y edad de 16-46 años (1). Con un rango de 0 a 10, un cut-off≥6 ofreció una sensibilidad del 96,1%, una especificidad del 93,9% y una eficienca del 94,9%. El área bajo la curva ROC fue de 0,979. Conclusiones La validación interna de este modelo basado en signos y síntomas la faculta como herramienta muy útil para detectar precozmente IPA en otorrinolaringología y atención primaria (AU)

Background Peritonsillar infection (PTI) is a reason for urgent consultation due to intense throat discomfort. A delayed or inaccurate diagnosis can jeopardize the upper aerodigestive tract and be fatal in its evolution. Our objective was to develop a predictive model for the presence of IPA helping in its rapid detection. Patients and methods A 66-month retrospective observational study from 2017 was carried out in a county and tertiary referral hospitals, registering data from all patients diagnosed with PTI and a proportional volume of subjects with pharyngeal symptoms without PTI. Collection of clinical, exploratory and demographic data among participants. Their higher relative risk of PTI presence allowed them to be considered as variables to be tested. Development of a scoring scale for the probability of suffering from it and logistic regression analysis, obtaining the ROC curve with the best diagnostic correlation. Internal validation and estimation of the predictive values of the model. Results On 348 cases of PTI, the assessment scale scored the presence of six variables: trismus (3), unilateral dysphagia-odynophagia (2), velar bulging (2), reflex otalgia (1), pharyngolalia (1) and age between 16 and 46 years (1). With a range of 0-10, a cut-off ≥6 offered a sensitivity of 96.1%, a specificity of 93.9%, and an efficiency of 94.9%. The area under the ROC curve was 0.979. Conclusions The internal validation of this model based on signs and symptoms makes it a very useful tool for early detection of PTI in otorhinolaryngology and primary care (AU)

Thixotropic Hydrogels Based on Laponite® and Cucurbituril for Delivery of Lipophilic Drug Molecules.

Nowadays the use of hydrogels for biomedical purposes is increasing because of their interesting features that allow the development of targeted drug delivery systems. Herein, hydrogel based on Laponite® (Lap) clay mineral as gelator and cucurbit[6]uril (CB[6]) molecules were synthetized for the delivery of flufenamic acid (FFA) for potential topical application. Firstly, the interaction between CB[6] and FFA was assessed by UV-vis spectroscopic measurements and molecular modeling calculations. Then, the obtained complex was used as filler for Lap hydrogel (Lap/CB[6]/FFA). The properties of the hydrogel in terms of viscosity and, self-repair abilities were investigated; its morphology was imaged by scanning electron and polarized optical microscopies. Furthermore, the changes in the hydrodynamic radii and in the colloidal stability of CB[6]/Lap mixture were investigated in terms of translational diffusion from dynamic light scattering and ζ-potential measurements. Finally, the kinetic in vitro release of FFA, from Lap/CB[6]/FFA hydrogel, was studied in a medium mimicking the pH of skin and the obtained results were discussed both by an experimental point of view and by molecular modeling calculations.

Validation of machine-learning model for first-trimester prediction of pre-eclampsia using cohort from PREVAL study.

OBJECTIVE: Effective first-trimester screening for pre-eclampsia (PE) can be achieved using a competing-risks model that combines risk factors from the maternal history with multiples of the median (MoM) values of biomarkers. A new model using artificial intelligence through machine-learning methods has been shown to achieve similar screening performance without the need for conversion of raw data of biomarkers into MoM. This study aimed to investigate whether this model can be used across populations without specific adaptations. METHODS: Previously, a machine-learning model derived with the use of a fully connected neural network for first-trimester prediction of early (< 34 weeks), preterm (< 37 weeks) and all PE was developed and tested in a cohort of pregnant women in the UK. The model was based on maternal risk factors and mean arterial blood pressure (MAP), uterine artery pulsatility index (UtA-PI), placental growth factor (PlGF) and pregnancy-associated plasma protein-A (PAPP-A). In this study, the model was applied to a dataset of 10 110 singleton pregnancies examined in Spain who participated in the first-trimester PE validation (PREVAL) study, in which first-trimester screening for PE was carried out using the Fetal Medicine Foundation (FMF) competing-risks model. The performance of screening was assessed by examining the area under the receiver-operating-characteristics curve (AUC) and detection rate (DR) at a 10% screen-positive rate (SPR). These indices were compared with those derived from the application of the FMF competing-risks model. The performance of screening was poor if no adjustment was made for the analyzer used to measure PlGF, which was different in the UK and Spain. Therefore, adjustment for the analyzer used was performed using simple linear regression. RESULTS: The DRs at 10% SPR for early, preterm and all PE with the machine-learning model were 84.4% (95% CI, 67.2-94.7%), 77.8% (95% CI, 66.4-86.7%) and 55.7% (95% CI, 49.0-62.2%), respectively, with the corresponding AUCs of 0.920 (95% CI, 0.864-0.975), 0.913 (95% CI, 0.882-0.944) and 0.846 (95% CI, 0.820-0.872). This performance was achieved with the use of three of the biomarkers (MAP, UtA-PI and PlGF); inclusion of PAPP-A did not provide significant improvement in DR. The machine-learning model had similar performance to that achieved by the FMF competing-risks model (DR at 10% SPR, 82.7% (95% CI, 69.6-95.8%) for early PE, 72.7% (95% CI, 62.9-82.6%) for preterm PE and 55.1% (95% CI, 48.8-61.4%) for all PE) without requiring specific adaptations to the population. CONCLUSIONS: A machine-learning model for first-trimester prediction of PE based on a neural network provides effective screening for PE that can be applied in different populations. However, before doing so, it is essential to make adjustments for the analyzer used for biochemical testing. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Thixotropic Hydrogels Based on Laponite® and Cucurbituril for Delivery of Lipophilic Drug Molecules.

Invited for this month's cover are the collaborating groups of Prof. Serena Riela at University of Catania, Prof. César Viseras at University of Granada and Dr. Ignacio Sainz-Diaz at Instituto Andaluz de Ciencias de la Tierra. The cover picture shows the possible application of the developed system. In particular, flufenamic acid, anti-inflammatory and anti-pyretic drug, was complexed into cucurbituril cavity and the supramolecular system obtained was used as filler for laponite® hydrogel for its topical delivery. More information can be found in the Research Article by Viseras-Iborra, Riela, and co-workers.

[Design of a predictive score table for peritonsillar infection based on signs and symptoms]. / Elaboración de una escala de puntuación predictiva de infección periamigdalina basada en signos y síntomas.

BACKGROUND: Peritonsillar infection (PTI) is a reason for urgent consultation due to intense throat discomfort. A delayed or inaccurate diagnosis can jeopardize the upper aerodigestive tract and be fatal in its evolution. Our objective was to develop a predictive model for the presence of IPA helping in its rapid detection. PATIENTS AND METHODS: A 66-month retrospective observational study from 2017 was carried out in a county and tertiary referral hospitals, registering data from all patients diagnosed with PTI and a proportional volume of subjects with pharyngeal symptoms without PTI. Collection of clinical, exploratory and demographic data among participants. Their higher relative risk of PTI presence allowed them to be considered as variables to be tested. Development of a scoring scale for the probability of suffering from it and logistic regression analysis, obtaining the ROC curve with the best diagnostic correlation. Internal validation and estimation of the predictive values of the model. RESULTS: On 348 cases of PTI, the assessment scale scored the presence of six variables: trismus (3), unilateral dysphagia-odynophagia (2), velar bulging (2), reflex otalgia (1), pharyngolalia (1) and age between 16 and 46 years (1). With a range of 0-10, a cut-off ≥6 offered a sensitivity of 96.1%, a specificity of 93.9%, and an efficiency of 94.9%. The area under the ROC curve was 0.979. CONCLUSIONS: The internal validation of this model based on signs and symptoms makes it a very useful tool for early detection of PTI in otorhinolaryngology and primary care.

Are farmers motivated to select for heat tolerance? Linking attitudinal factors, perceived climate change impacts, and social trust to farmers' breeding desires.

This study provides an understanding of dairy farmers' willingness to include heat tolerance in breeding goals and the modulating effect of sociopsychological factors and farm profile. A survey instrument including a choice experiment was designed to specifically address the trade-off between heat tolerance and milk production level. A total of 122 farmers across cattle, goat, and sheep farms were surveyed face-to-face. The results of the experiment show that most farmers perceive that heat stress and climate change are increasingly important problems, and that farming communities should invest more in generating knowledge and resources on mitigation strategies. However, we found limited initial support for selection for heat tolerance. This attitude changed when farmers were presented with objective information on the benefits and limitations of the different breeding choices, after which most farmers supported selection for heat tolerance, but only if doing so would compromise milk production gains to a small extent. Our results show that farmers' selection choices are driven by the interactions between heat stress risk perception, attitudes toward breeding tools, social trust, the species reared, and farm production level. In general, farmers willing to support selection of heat-tolerant animals are those with positive attitudes toward genetic values and genomic information and a strong perception of climate change and heat stress impacts on farms. On the contrary, negative support for selection for heat tolerance is found among farmers with high milk production levels; high trust in farming magazines, livestock farmers' associations, and veterinarians; and low trust in environmental and animalist groups.

Biochar as a sustainable alternative to carbon black in agricultural mulch films.

Examples of biochar as an alternative to traditional plastic fillers, like carbon black, are numerous and growing. However, in the agricultural mulch film application, both the polymer and its fillers are pushed to their mechanical limit to obtain an effective product, using the least amount of plastic. Through a combined techno-economic analysis (TEA) and life cycle assessment (LCA), this study characterizes the use of carbon-negative biochar as an opacity filler in mulch film applications. Due to its larger particle size, the biochar demands additional thickness to achieve equivalent opacity as carbon black in films. A thicker film translates to additional polymer demand, and a significant increase in price and environmental impact. A comparable formulation for an equal price ($623 per mulched ha) as a 2.6 wt % carbon black with 25 µm thickness was derived, needing 15 wt % biochar and a thickness of 30 µm. The biochar formulation resulted in a slightly higher global warming potential (3% increase), but much larger impact in the land use category (+339%), and the sample was deemed not fit for use in the intended mulch application. These results indicate that in applications where the polymeric matrix and its fillers are pushed to their mechanical limit, the displacement of traditional fillers by biochar is challenging. However, biochar derived from waste biomass (thus reducing land use impact) remains a valid, environmentally beneficial solution to displace traditional fillers for non-extreme plastic uses (commodity plastics) and thicker composites.

[The dramatic loss of statistical power when dichotomising continuous variables]. / La dramática pérdida de potencia estadística al dicotomizar variables continuas.

A very common practice in medical research, during the process of data analysis, is to dichotomise numerical variables in two groups. This leads to the loss of very useful information that can undermine the effectiveness of the research. Several examples are used to show how the dichotomisation of numerical variables can lead to a loss of statistical power in studies. This can be a critical aspect in assessing, for example, whether a therapeutic procedure is more effective or whether a certain factor is a risk factor. Dichotomising continuous variables is therefore not recommended unless there is a very specific reason to do so.

TITLE: La dramática pérdida de potencia estadística al dicotomizar variables continuas.Una práctica muy habitual en la investigación médica, durante el proceso de análisis de los datos, es dicotomizar variables numéricas en dos grupos. Dicha práctica conlleva la pérdida de información muy útil que puede restar eficacia a la investigación. A través de varios ejemplos, se muestra cómo con la dicotomización de variables numéricas los estudios pierden potencia estadística. Esto puede ser un aspecto crítico que impida valorar, por ejemplo, si un procedimiento terapéutico es más efectivo o si un determinado factor es de riesgo. Por tanto, se recomienda no dicotomizar las variables continuas si no existe un motivo muy concreto para ello.

Mitos y realidad en el cálculo del tamaño muestral / Myths and reality about calculating sample size

Cuando decidimos hacer un estudio, una de las primeras cuestiones que se plantea es ¿qué número de individuos debo incluir en la muestra para que sea ‘representativa’ y el estudio sea ‘válido’? Como en otros ámbitos de la vida, hay muchas cuestiones para las que no hay una cantidad ‘adecuada’ y son válidas diferentes cantidades. Aquí ocurre lo mismo. La pregunta ‘¿cuántos euros costó esta bicicleta?’ tiene como respuesta un número concreto. Pero la pregunta ‘¿cuántos euros necesito para comprar una bicicleta?’ admite muchas cifras distintas como respuesta, dependiendo del tamaño y otras características de la bicicleta. Los libros de estadística contienen fórmulas que relacionan el tamaño de la muestra con ciertos parámetros y la mayoría de los médicos cree que una de ellas les dará el tamaño ‘adecuado’ para su investigación, y que usándolas queda ‘justificado el tamaño de la muestra’ ante posibles revisores. En este documento se hace una reflexión sobre el verdadero peso que tienen dichas fórmulas y cuál debe ser el uso adecuado que el investigador haga de ellas. Es necesario mostrar errores y simulaciones que no benefician a nadie y perjudican a muchos restando tiempo y energía.(AU)

When we decide to conduct a study, one of the first questions that arises is what number of individuals should be included in the sample for it to be ‘representative’ and for the study to be ‘valid’? As in other areas of life, there are many matters for which there is no ‘right’ amount and different quantities are valid. The same applies here. When asked the question ‘How many euros did this bicycle cost?’, the answer is a definite number. But the question ‘How many euros do I need to buy a bicycle?’ can be answered in many different ways, depending on the size and other characteristics of the bicycle. Statistics textbooks contain formulas relating sample size to certain parameters and most doctors believe that one of these will give them the ‘right’ size for their research, and that by using them their choice of sample size will be justified in the eyes of potential reviewers. This document reflects on the true value of these formulas and how researchers should make proper use of them. It is necessary to show errors and simulations that benefit no one and hinder many by taking up large amounts of time and energy.(AU)

A microfluidic labyrinth self-assembled by a chemical garden.

Chemical gardens, self-assembling precipitates that spontaneously form when a metal salt is added to a solution of another precipitating anion, are of interest for various applications including producing reactive materials in controlled structures. Here, we report on two chemical garden reaction systems (CuCl2 and Cu(NO3)2 seed crystals submerged in sodium silicate) that produced self-assembled microfluidic labyrinths in a vertical 2D Hele-Shaw reactor. The formation of labyrinths as well as the specific growth modes of the precipitate were dependent on the silicate concentration: CuCl2 labyrinths formed only at 3 and 4 M silicate and Cu(NO3)2 labyrinths formed only at 4 and 5 M silicate. The labyrinth structures contained silicate on the exterior and crystalline material interpreted as hydrated minerals from the metal salt in their interiors. The bubble-guided tubes that form labyrinths can be controlled by changing the angle of the 2D reaction cell; this suggests that future experiments of this type could form self-organizing structures with controlled composition and orientation for use in microfluidics and various materials science applications.