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Introduction: Globally, up to 76.6% of the population may be affected by vitamin D (VD) deficiency, which has been linked to increased morbidity and mortality from COVID-19. This underscores the importance of further research into VD supplementation, particularly for health care workers, who are at higher risk due to indoor work environments and dietary challenges associated with shift schedules. Objective: This study aimed to identify factors associated with VD deficiency in Mexican health care workers exposed to SARS-CoV-2. Materials and methods: We conducted a cross-sectional study from June 2020 to January 2021 among frontline health care workers treating hospitalized COVID-19 patients. Blood samples were collected to measure 25-hydroxy VD levels via radioimmunoassay. We also assessed previous COVID-19 infection and comorbidities that could influence VD levels. Results: The study included 468 health care workers. The median serum VD concentration was 16.6 ng/mL. VD deficiency was found in 69.4% (n = 325) of participants, while only 5.1% (n = 24) had normal levels. Those with type 2 diabetes (13.3 ng/mL vs. 17.1 ng/mL) or obesity (15.7 ng/mL vs. 17.1 ng/mL) had significantly lower VD levels than their counterparts (p < 0.001 and p = 0.049, respectively). No significant differences were found among participants with high blood pressure. Multivariate analysis revealed that type 2 diabetes was independently associated with VD deficiency. Conclusion: There is a high prevalence of VD deficiency among health care workers, which is potentially linked to both personal health factors and occupational conditions.

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Introduction: Vitamin D (VD) deficiency is common in children with chronic kidney disease (CKD) because of multiple factors. During the coronavirus disease 2019 (COVID-19) pandemic, it increased because of medicine shortage and no enough medical service for patients with non-COVID-19 diseases. Objective: To analyze the effects of the COVID-19 pandemic-related lockdown on the serum levels and status of 25-hydroxyvitamin D3 (25-[OH]D) in children with CKD. Materials and methods: This retrospective study included patients (6-18 years old) who were diagnosed with CKD stage 2-5 and routinely measured for serum VD levels between May 2019 and December 2022. Serum 25-(OH)D levels were measured before, during, and after the pandemic (2019, 2020-2021, and 2022, respectively). The daily dose of cholecalciferol supplementation and the readjustment (if required) were recorded. Results: This study included 171 patients (median age: 12 years). Before the pandemic, the median serum VD level was 25.0 ng/mL (19.3% VD deficiency). Then, VD supplementation was adjusted to 400-1,200 UI daily in 98.8% (n = 169) of patients. During the pandemic, the median VD level decreased to 22.5 ng/mL (43.3% VD deficiency). Hence, the supplementation was readjusted, and after the pandemic, the level was 28.7 ng/mL (18.7% VD deficiency), indicating a statistically significant increase in serum VD levels from the prepandemic period (p = 0.007). Conclusion: Decreased serum VD levels and increased VD deficiency frequency were observed in patients with CKD during the COVID-19 but improved after readjustment of supplementation.

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We thank the group headed by Jorge Valencia Alonso for taking the time to review in detail and prepare the letter about our article entitled: " Bibliometric analysis of scientific publications on COVID-19 elaborated by staff of the Instituto Mexicano del Seguro Social", which has recently been published in the Medical Journal of the Mexican Social Security Institute. Based on your observations and comments, we allow ourselves to make the following clarifications following the same sequence of your letter to the Editor.

Agradecemos al grupo encabezado por Jorge Valencia Alonso por tomarse el tiempo para revisar con detalle y elaborar la carta sobre nuestro artículo titulado: "Análisis bibliométrico de las publicaciones científicas sobre COVID-19 por personal del IMSS", que recientemente se ha publicado en la Revista Médica del Instituto Mexicano del Seguro Social. De acuerdo con sus observaciones y comentarios, nos permitimos realizar las siguientes aclaraciones siguiendo la misma secuencia de su carta al Editor.

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Introduction: Multisystem inflammatory syndrome in children associated with coronavirus disease 2019 (MIS-C), a novel hyperinflammatory condition secondary to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, is associated with severe outcomes such as coronary artery aneurysm and death. Methods: This multicenter, retrospective, observational cohort study including eight centers in Mexico, aimed to describe the clinical characteristics and outcomes of patients with MIS-C. Patient data were evaluated using latent class analysis (LCA) to categorize patients into three phenotypes: toxic shock syndrome-like (TSSL)-MIS-C, Kawasaki disease-like (KDL)-MIS-C, and nonspecific MIS-C (NS-MIS-C). Risk factors for adverse outcomes were estimated using multilevel mixed-effects logistic regression. Results: The study included 239 patients with MIS-C, including 61 (26%), 70 (29%), and 108 (45%) patients in the TSSL-MIS-C, KDL-MIS-C, and NS-MIS-C groups, respectively. Fifty-four percent of the patients were admitted to the intensive care unit, and 42%, 78%, and 41% received intravenous immunoglobulin, systemic glucocorticoids, and anticoagulants, respectively. Coronary artery dilatation and aneurysms were found in 5.7% and 13.2% of the patients in whom coronary artery diameter was measured, respectively. Any cause in-hospital mortality was 5.4%. Hospitalization after ten days of symptoms was associated with coronary artery abnormalities (odds ratio [OR] 1.6, 95% confidence interval [CI] 1.2-2.0). Age ≥10 years (OR: 5.6, 95% CI: 1.4-2.04), severe underlying condition (OR: 9.3, 95% CI: 2.8-31.0), platelet count <150,000 /mm3 (OR: 4.2, 95% CI: 1.2-14.7), international normalized ratio >1.2 (OR: 3.8, 95% CI: 1.05-13.9), and serum ferritin concentration >1,500 mg/dl at admission (OR: 52, 95% CI: 5.9-463) were risk factors for death. Discussion: Mortality in patients with MIS-C was higher than reported in other series, probably because of a high rate of cases with serious underlying diseases.

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Background: Adipokines are associated with cardiovascular disease; in chronic kidney disease (CKD) patients adipokines could be useful prognostic factors. Objectives: To explore whether leptin and adiponectin in kidney replacement therapy (KRT) children could have a role on their cardiac function, in the long-term. Design: Prospective cohort study was performed with pediatric KRT patients, aged 8 to 17 years who were undergoing hemodialysis or peritoneal dialysis. At enrollment, lipid profile, adipokines (leptin, leptin receptor, free leptin, and adiponectin), anthropometric measurements and cardiological evaluation were determined. At two-year follow-up, a new cardiological evaluation was performed. Statistical analysis: Quantitative data are presented as median and interquartile range (IQR). Mann-Whitney U test and Chi-squared were used for the between-group comparison. Multivariate analyzes were performed to determine the association of adipokines levels with ventricular ejection fraction (LEVF). Results: We included 56 patients, with a median age of 12.5 years. In the first cardiological evaluation, median LVEF was 70.0% (IQR 61%, 76%), 20 patients (35.7%) had some cardiovascular condition, and 10 (17.8%) altered LVEF. At 24-month follow-up, the median LVEF was 70.5% (IQR 65.1%, 77%), while the delta-LVEF values was 3% (IQR -6.5%, 7%). Delta-LVEF were correlated with baseline adipokines serum levels, and the only positive correlation found was with free leptin (r=0.303, p=0.025). In multivariate analysis, levels of free leptin (Coef. 0.12, p<0.036) and leptin (coef. 1.72, p=0.049), as well as baseline LVEF (Coef. -0.65, p<0.001) were associated with delta-LVEF. Conclusions: Free leptin, leptin and LVEF at the beginning of follow-up were associated with the LVEF decrease at the 24-month follow-up in KRT children.

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Objective: To determine if the leptin, adiponectin, and leptin/adiponectin ratio (LAR) can predict weight gain at the end of GnRH analogs (GnRHa) treatment in girls with central precocious puberty (CPP). Material and methods: Study design: prospective cohort. Serum levels of leptin and adiponectin were determined at diagnosis of CPP. Anthropometry was performed at diagnosis of CPP and every six-months, until treatment with GnRHa was discontinued and they presented menarche. Patients were divided according to BMI<94 and BMI>95 percentile at diagnosis of CPP. The outcome was the increased in weight gain (e.g., from normal weight to overweight) at the end of follow-up. Statistical analysis: repeated measures ANOVA test and Student's t-test were used to compare groups. Logistic regression analysis was used to evaluate the association of leptin and adiponectin levels, as well as LAR values with increased weight gain. Results: Fifty-six CPP patients were studied, 18 had BMI >95 percentile and 38 BMI <94 percentile. Of the 18 patients who initially had BMI >95th, two patients went from obesity to overweight, while among the 38 patients who started with BMI <94th, 21 (55.2%) increased their weight gain at the end of follow-up. This last group had higher leptin levels (8.99 ± 0.6 vs 6.14 ± 0.8, p=0.005) and higher LAR values compared to those who remained in the same weight (1.3 ± 0.5 vs 0.96 ± 0.56, p=0.01). In the logistic regression analysis, it was found that higher leptin levels and higher LAR values were associated with increased weight gain (RR 1.31, 95%CI 1.03-1.66, RR 4.86, 95%CI 1.10-21.51, respectively), regardless of birth weight, pubertal stage, age, and bone/chronological age ratio. Conclusions: In patients with CPP, leptin levels and higher LAR values appear to be associated with significantly greater weight gain during GhRHa treatment, particularly in girls starting with BMI < 94 percentile.

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Background: Since the beginning of the pandemic, new knowledge about COVID-19 obtained by research has been disseminated in medical and scientific journals, but the large number of publications that have been generated in such a short time has been impressive. Objective: To perform a bibliometric analysis of the published articles in medical-scientific journals carried-out by the Mexican Social Security Institute (IMSS) personnel on COVID-19. Material and methods: Systematic review of the literature, identifying the publications included in the PubMed and EMBASE databases, up to September 2022. Articles on COVID-19 were included, in which at least one author had IMSS affiliation; there was no restriction on the type of publication, so original articles, review articles, clinical case reports, etc. were included. The analysis was descriptive. Results: 588 abstracts were obtained, of which 533 full length articles met the selection criteria. Most were research articles (48%), followed by review articles. Mainly clinical or epidemiological aspects were addressed. They were published in 232 different journals, with a predominance of foreign journals (91.8%). Around half of the publications were carried out by IMSS personnel together with authors from other institutions, national or foreign. Conclusions: The scientific contributions prepared by IMSS personnel have contributed to understanding clinical, epidemiological and basic aspects of COVID-19, which has had an impact on improving the quality of care for its beneficiaries.

Introducción: desde el inicio de la pandemia los nuevos conocimientos sobre COVID-19 han sido difundidos en revistas médico-científicas, y ha sido impresionante la gran cantidad de publicaciones que se ha generado en tan poco tiempo. Objetivo: realizar un análisis bibliométrico de los artículos publicados en revistas médico-científicas elaborados por personal del Instituto Mexicano del Seguro Social (IMSS) sobre COVID-19. Material y métodos: revisión sistemática de la literatura, identificando las publicaciones incluidas en las bases de datos PubMed y EMBASE, hasta septiembre de 2022. Se incluyeron los artículos sobre COVID-19 en los que al menos un autor tuviera adscripción IMSS, sin restricción del tipo de publicación, por lo que se incluyeron artículos originales, de revisión, reportes de casos clínicos, etc. El análisis fue de tipo descriptivo. Resultados: se obtuvieron 588 resúmenes, de los cuales 533 artículos cumplieron con los criterios de selección. La mayoría correspondió a artículos de investigación y revisión. Principalmente se abordaron aspectos clínicos o epidemiológicos. Se publicaron en 232 revistas diferentes, predominando revistas extranjeras (91.8%). Alrededor de la mitad de las publicaciones fueron realizadas por personal del IMSS en conjunto con autores de otras instituciones, nacionales o extranjeras. Conclusiones: las aportaciones científicas elaboradas por personal del IMSS han contribuido a conocer aspectos clínicos, epidemiológicos y básicos sobre COVID-19, lo cual ha impactado en la mejora de la calidad de atención de sus derechohabientes.

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OBJECTIVE: To report the frequency of asymptomatic infection with SARS-CoV-2 in pediatric patients undergoing invasive medical procedures in a tertiary pediatric hospital. METHODS: From June to October 2020, a SARS-CoV-2 real-time reverse-transcription polymerase chain reaction (rRT-PCR) test was performed for all pediatric patients scheduled to undergo an elective invasive procedure. None of the patients was symptomatic. The cycle threshold (Ct) values of the ORF1ab gene were recorded for all patients. RESULTS: A total of 700 patients were screened for SARS-CoV-2 infection. The median age was 5.7 y old. In total, 46.6% (n = 326) of the patients were male, and 53.4% (n = 374) were female. The most common underlying diseases were hemato-oncological (25.3%), gastrointestinal (24.9%), and genitourinary (10.3%). The main scheduled surgical-medical procedures were surgical treatment for acquired congenital diseases, biopsy sampling, local therapy administration, organ transplantation, and the placement of central venous catheters, among others. The SARS-CoV-2 rRT-PCR test was positive in 9.4% (66), and the median Ct value was 35.8. None of the patients developed COVID-19. CONCLUSIONS: The frequency of asymptomatic SARS-CoV-2 infection was detected in less than 10% of pediatric patients scheduled to undergo an elective invasive procedure in a tertiary hospital. This frequency is higher than those in reports from different countries.

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In developing a research protocol, authors must consider the possible errors that may occur throughout the study. In clinical research, two types of biases are recognized: random errors and systematic errors; the latter are called biases. To date, dozens of biases have been described, which is why the purpose of this article is to describe the main biases that can occur in clinical research studies, as well as strategies to avoid them or to minimize their effects. Since there are several classifications, in order to provide a more practical overview in this review, the biases are grouped into three types: selection biases, information (or performance) biases, and confounding biases. In addition, to make it even more specific, we describe the biases considering the purpose of the research: prognosis, therapeutics, causality, and diagnostic test studies.

En la elaboración de un protocolo de investigación, los autores deben tomar en cuenta los posibles errores que puedan ocurrir a lo largo del estudio. En la investigación clínica se reconocen dos tipos: los errores aleatorios y los errores sistemáticos, estos últimos se denominan sesgos. A la fecha se han descrito decenas de sesgos, por lo que este artículo tiene como objetivo describir los principales sesgos que pueden ocurrir en los estudios de investigación clínica, así como la forma para evitarlos o minimizar sus efectos. En virtud de que existen varias clasificaciones, en la presente revisión y, a fin de disponer un panorama más práctico, los sesgos se agrupan en tres: sesgos de selección, sesgos de información (o ejecución) y sesgos de confusión. Además, para una descripción más específica, se toma en cuenta el propósito del estudio: pronóstico, terapéutica, causalidad y la evaluación de una prueba diagnóstica.

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BACKGROUND/OBJECTIVES: Considering the high number of deaths from coronavirus disease 2019 (COVID-19) in Latin American countries, together with multiple factors that increase the prevalence of vitamin D deficiency, we aimed to determine 25-hydroxyvitamin D (25[OH]D) levels and its association with mortality in patients with critical COVID-19. SUBJECTS/METHODS: This was a prospective observational study including adult patients with critical COVID-19. Data, including clinical characteristics and 25(OH)D levels measured at the time of intensive care unit admission, were collected. All patients were followed until hospital discharge or in-hospital death. The patients were divided into those surviving and deceased patient groups, and univariate and multivariate logistic regression analyses were performed to determine independent predictors of in hospital mortality. RESULTS: The entire cohort comprised 94 patients with critical COVID-19 (males, 59.6%; median age, 61.5 years). The median 25(OH)D level was 12.7 ng/mL, and 15 (16%) and 79 (84%) patients had vitamin D insufficiency and vitamin D deficiency, respectively. The median serum 25(OH)D level was significantly lower in deceased patients compared with surviving (12.1 vs. 18.7 ng/mL, P < 0.001). Vitamin D deficiency was present in 100% of the deceased patients. Multivariate logistic regression analysis revealed that age, body mass index, other risk factors, and 25(OH)D level were independent predictors of mortality. CONCLUSIONS: Vitamin D deficiency was present in 84% of critical COVID-19 patients. Serum 25(OH)D was independently associated with mortality in critical patients with COVID-19.

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Informing in the studies about the effect size of an intervention or the impact of the factor(s) about an outcome, allows better decision-making for the application of the results in clinical practice. This article presents different methods to analyze the effect size, which can be through direct or indirect statistical methods. Within the direct methods, there's the difference in means between groups and the difference of absolute or relative frequencies. Among the indirect methods, Cohen's "d" family (which are based on standard deviation values), the "r and R2" family, measures of association (e.g. OR, RR, HR), and impact measures (e.g. NNT) are shown. The decision to use any of these methods depends on the objectives of the study and the measuring scale that is used to assess the results, as well as the data distribution. In order to enhance the understanding of the methods described in this article, examples are included, and the need to include level of precision (e.g. confidence intervals) is highlighted, along with the clinical decision thresholds for a better interpretation.

Informar en los estudios sobre el tamaño del efecto de una intervención o del impacto de factor(es) sobre un desenlace, permite tomar mejores decisiones para la aplicación de los resultados a la práctica clínica. En este artículo se presenta la manera de analizar el tamaño del efecto, lo cual puede ser mediante métodos estadísticos directos o indirectos. Dentro de los métodos directos, se encuentra la diferencia de promedios entre grupos y la diferencia de frecuencias absolutas o relativas. Dentro de los métodos indirectos se muestran los índices de la familia de "d" de Cohen (que se basan en valores de desviación estándar), la familia de "r y R2", medidas de asociación (RM, RR, HR) e impacto (NNT). La decisión del uso de cualquiera de los métodos descritos, depende de los objetivos del estudio, la escala de medición usada para evaluar los resultados y la distribución de los datos. Para facilitar la comprensión, se incluyen ejemplos y se resalta la necesidad de incluir los diferentes estadísticos con su nivel de precisión (ej. intervalos de confianza), junto con los umbrales clínicos de decisión, a fin de mejorar su interpretación.

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The practice of evidence-based medicine includes the critical analysis of clinical research studies, and, within it, the interpretation of the results reported. In addition, to statistical data, there are estimators that can help clinicians transfer research findings to routine clinical practice. These estimators are measures of risk, association, and impact. Risk measures report current uncertainty or probability (prevalence of a disease, sensitivity, specificity) or for future events (cumulative incidence, incidence density). Measures of association are related to the identification of the risk in order to determine whether certain factors increase or decrease the probability of development of a disease (relative risk, odds ratio, hazard ratio). While measures of impact allow, among other things, to estimate the effect of a treatment (relative risk reduction, absolute risk reduction, number needed to treat). In this review, each of these estimators is described, defined, and presented with examples.

Parte del ejercicio de la medicina basada en evidencia incluye el análisis crítico de los estudios de investigación clínica y dentro de este, la interpretación de los resultados presentados. Además de los datos estadísticos, existen estimadores que pueden ayudar a los clínicos a trasladar los hallazgos de las investigaciones a la práctica clínica habitual. Estos estimadores son las medidas de riesgo, asociación e impacto. Las medidas de riesgo informan sobre la incertidumbre o probabilidad en el presente (prevalencia de una enfermedad, sensibilidad, especificidad) o para eventos futuros (incidencia acumulada, densidad de incidencia). Las medidas de asociación se relacionan con la identificación del riesgo para determinar si ciertos factores aumentan o disminuyen la probabilidad del desarrollo de una enfermedad (riesgo relativo, razón de momios, cociente de riesgo). Mientras que las medidas de impacto permiten, entre otros, estimar el efecto de un tratamiento (reducción del riesgo relativo, reducción del riesgo absoluto, número necesario por tratar). En esta revisión se describen, definen y presentan ejemplos de cada uno de estos estimadores.

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BACKGROUND: Falls are a significant public health problem among older people worldwide. The aim was to perform a new systematic review and meta-analysis to assess whether cataract surgery is effective in reducing the rate of falls in older persons. METHODS: The systematic review was performed following the recommendations by the Cochrane Collaboration. Original papers were included with RCT or quasi-experimental design, which described the effect on uni- or bilateral cataract surgery on the rate of falls among people aged 60 or older. Titles and abstracts were reviewed, full-text versions were retrieved, and two independent examiners reviewed them to assess inclusion criteria. All relevant variables were synthesised in an evidence table. Random-effects meta-analyses were performed pooling the trials, and results were expressed as relative risk (RR) and 95% confidence intervals. RESULTS: The initial search reported 99 potential abstracts, and 41 full-text versions were examined. In the end, eight studies were included. Five included patients 65 years of age and older, two patients 55 years and older, and one included patients 50 years or older. Phacoemulsification and intraocular lens implant were performed in all studies. Two were RCT, and six were quasi-experimental. Falls was the main outcome. The six quasi-experimental studies reported that a reduction in the frequency of falls was observed (RR 0.68, 95% CI 0.48-0.96), although heterogeneity was significant (I 2 = 74%). Only one RCT reported risk reduction of 34% (RR 0.66, 95% CI 0.45-0.96). CONCLUSIONS: This meta-analysis provides evidence that the first cataract surgery reduces the frequency of falls in older people with bilateral cataracts, but a second surgery does not have significant impact.

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Diagnostic tests make it possible to determine whether a person has a disease or not. Before incorporating a new diagnostic test in the clinical setting, it is necessary to define its validity through its indicators of performance, sensitivity, and specificity. In these studies, like in any research, the results might not be reliable when there are biases during their execution. This article entails the discussion about the biases in diagnostic test studies that may cause inaccuracy in sensitivity and specificity. The main biases that affect the validity of these studies are: incorporation bias, partial and/or differential verification bias, an imperfect reference standard, a limited spectrum of the disease, and the ambiguous results of the test to be validated. In addition, examples of how these biases impact on the results of sensitivity and specificity are given in this paper.

Las pruebas de diagnóstico permiten determinar si una persona tiene o no una enfermedad. Para incorporar una nueva prueba de diagnóstico en el ámbito clínico primero es necesario definir su validez a través de sus indicadores de desempeño, sensibilidad y especificidad. Como en cualquier investigación, en este tipo de estudios es posible que los resultados no sean confiables cuando hay sesgos durante su ejecución. En este artículo se discuten los sesgos en estudios de prueba diagnóstica que pueden ocasionar que la sensibilidad y especificidad no sean correctas. Los principales sesgos que afectan la validez en estos estudios son el sesgo de incorporación, la verificación parcial o diferencial, un estándar de oro imperfecto, un espectro limitado de la enfermedad y los resultados ambiguos de la prueba por validar. Además, en este artículo se dan ejemplos de cómo impactan estos sesgos en la sensibilidad y especificidad.

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Systematic reviews are secondary investigations that compile published results that have been obtained from studies involving human subjects. Meta-analysis is the term used to describe the carrying out of statistical analysis of the combination of the results of two or more original studies, which had to be selected from a systematic review. In this way, a meta-analysis cannot exist without a systematic review. Systematic reviews arise due to the exponential increase in the information; to provide all health personnel with a study that critically analyzes the results and discriminates those that may be useful in clinical practice. Systematic reviews are one of the fundamental tools in evidence-based medicine, in which two of the main steps refer to both the search and the critical analysis of the studies, which shall support medical decisions on aspects that are mainly related to diagnosis, treatment, or prognosis. On the other hand, systematic reviews have been essential for some time now when developing evidence-based clinical practice guidelines and they can be used to make decisions on health policies. The methodology for performing and interpreting systematic reviews and meta-analysis is described in this article.

Las revisiones sistemáticas son investigaciones secundarias que compilan los resultados publicados obtenidos a partir de estudios en seres humanos. El término metaanálisis es utilizado para describir el análisis estadístico de la combinación de los resultados de dos o más estudios originales, los cuales debieron ser seleccionados a partir de una revisión sistemática. De esta forma, no puede haber metaanálisis sin una revisión sistemática. Las revisiones sistemáticas surgen debido al incremento exponencial de la información, para facilitar un estudio que analice críticamente los resultados y discrimine los que puedan ser útiles en la práctica clínica. Las revisiones sistemáticas son una de las herramientas fundamentales en la medicina basada en evidencia, en la cual dos de los pasos principales se refieren a la búsqueda y lectura crítica de los estudios, que apoyarán las decisiones médicas sobre aspectos relacionados principalmente con el diagnóstico, tratamiento o pronóstico. Por otro lado, desde hace tiempo, las revisiones sistemáticas son imprescindibles al elaborar guías de práctica clínica basadas en evidencia y pueden ser utilizadas para tomar decisiones en políticas de salud. En este artículo se describe la metodología para la realización e interpretación de revisiones sistemáticas y metaanálisis.

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Ecological studies are one of the most common study designs used to establish the association between certain factors and disease development. However, they have limitations mainly on how to measure the variables, so their results must be verified in studies with greater validity. Therefore, the study that links the possible relationship between higher mortality from COVID-19 and non-vaccination by bacillus Calmette-Guérin (BCG) that was recently published, remains in doubt due to the lack of rigor in the methodology used.

Los estudios ecológicos son uno de los diseños más frecuentemente empleados para tratar de establecer la asociación de ciertos factores con el desarrollo de enfermedades. Sin embargo, tienen limitaciones principalmente en la forma de realizar las mediciones de las variables, por lo que sus resultados tienen que ser comprobados con estudios de mayor calidad. Por lo tanto, el estudio recientemente publicado que vincula la posible relación entre una mayor mortalidad por COVID-19 y la no vacunación con el bacilo de Calmette-Guérin (BCG) queda en duda debido a la falta de rigurosidad en la metodología empleada.

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In general, diagnostic tests are the necessary tools to determine the presence or absence of illness, but they can be useful also for excluding other differential conditions, assessing severity, establishing specific treatments, and estimating possible prognosis results. In order to determine how much a new diagnostic test can contribute in the clinical setting, studies with different research designs and populations are required. Since it might be complex to understand the development process of a diagnostic test based on its initial stages, this article synthesizes and gives examples of the four phases that have been proposed to define this process. The goals of these four phases are: phase I, establishing reference values; phase II, analyzing the validity of the test; phase III, the impact of its incorporation in diagnostic-therapeutic plans; and phase IV, a long-term assessment after incorporating the diagnostic test.

Generalmente, las pruebas de diagnóstico son las herramientas necesarias para determinar la presencia o no de enfermedad, pero también pueden ser útiles para la exclusión de otras entidades diferenciales, evaluar la gravedad, establecer tratamientos específicos y estimar posibles resultados pronóstico. Para determinar cuánto puede contribuir una nueva prueba de diagnóstico en el ámbito clínico, se requieren estudios con diseños de investigación y poblaciones diferentes. Dado que puede resultar complejo entender el desarrollo de una prueba diagnóstica a partir de sus fases iniciales, en este artículo se sintetizan y se proporcionan ejemplos de las cuatro fases que se han propuesto para definir este proceso. Las metas de estas etapas son las siguientes: fase I, establecimiento de valores de referencia; fase II, análisis de la validez de la prueba; fase III, impacto de su incorporación en el plan diagnóstico; fase IV, evaluación a largo plazo de la incorporación de las prueba diagnóstica.

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Clinical trials become very relevant in the development of new drugs when their pharmacokinetics, pharmacodynamics, efficiency, safety and possible adverse effects are being assessed. So new drugs are available for their daily use in patients, a model has been proposed for more than four decades; This model consists in the realization of sequential research studies, which were called clinical phases I, II, III and IV, which begin once the drugs' effects have been verified in cellular and animal models (preclinical phase). In this article, the general characteristics of each of the clinical phases are synthesized but, apart from that, the modifications that have been done over the years are described with the purpose of making new drugs available in a quicker way.

Los ensayos clínicos toman gran relevancia en el desarrollo de nuevos fármacos al evaluar la farmacocinética, farmacodinamia, eficacia, seguridad y sus posibles efectos adversos. Para que un nuevo fármaco esté disponible para su uso cotidiano en pacientes, desde hace más de cuatro décadas se propuso un modelo que consiste en la realización de estudios de investigación secuenciales que se denominaron fases clínicas I, II, III y IV, las cuales se inician una vez que se han comprobado los efectos del fármaco en modelos celulares y animales (fase preclínica). En este artículo se sintetizan las características generales de cada una de las fases clínicas, pero además se describen las modificaciones que se han realizado en el trascurso de los años, a fin de disponer rápidamente de nuevos fármacos.

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INTRODUCTION: Objective: to identify the factors related to the presence of hospital malnutrition (HM) in patients under five years of age hospitalized in a third level care unit. Material and methods: cohort study. Patients under five years of age hospitalized were included. The record identified age, sex, pathological history, reason for admission and nutritional status by calculating weight/age (W/A), height/age (H/A) and weight/height (W/H). The entire somatometry intake process was performed upon admission, and was repeated on days 2, 4 and 7 of follow-up. The HM was defined as a decrease of more than 0.25 standard deviations in the W/H after seven days of hospitalization. Results: eighty-three patients were identified. The reason for admission was non-surgical pathology in 77% (n = 64). Seventy per cent (n = 58) had underlying disease. At the time of admission, 66% (n = 55) presented malnutrition. A progressive decrease in the Z score of W/H was observed as hospitalization progressed (p < 0.001). An incidence of 67.5% of HM was identified. It was shown that the presence of malnutrition at admission of hospitalization increased the risk of HM (OR 2.9, 95% CI 1.05 to 8.10, p = 0.03). In patients with malnutrition from admission, an age younger than two years decreased the risk of HM (OR 0.093, 95% CI 0.009 to 0.959, p = 0.046), while the underlying disease increased the risk (OR 6.34, 95% CI 1.009 to 39.89, p = 0.049). Conclusions: the presence of malnutrition and underlying disease prior to admission were risk factors to present HM.

INTRODUCCIÓN: Objetivo: identificar los factores relacionados con la presencia de desnutrición hospitalaria (DH) en pacientes menores de cinco años hospitalizados en una unidad de tercer nivel de atención. Material y métodos: estudio de cohorte. Se incluyeron pacientes menores de cinco años de edad hospitalizados. Del expediente se identificaron la edad, el sexo, los antecedentes patológicos, el motivo de ingreso y el estado nutricional mediante el cálculo de los índices peso/edad (P/E), talla/edad (T/E) y peso/talla (P/T). El proceso de toma de somatometría completa se realizó al ingreso y se repitió en los días 2, 4 y 7 de seguimiento. La DH se definió como disminución de más de 0,25 desviaciones estándar en el índice de P/T después de siete días de hospitalización. Resultados: se identificaron 83 pacientes. El motivo de ingreso fue patología no quirúrgica en un 77% (n = 64). El 70% (n = 58) presentaba alguna enfermedad subyacente. Al momento del ingreso, el 66% (n = 55) tenía desnutrición. Se observó una disminución progresiva del score Z de P/T conforme avanzó el tiempo de hospitalización (p < 0,001). Se identificó una incidencia del 67,5% de DH. Se demostró que la presencia de desnutrición al ingreso de la hospitalización aumentaba el riesgo de DH (OR 2,9, IC 95% 1,05 a 8,10, p = 0,03) y en los pacientes con desnutrición desde el ingreso una edad menor a dos años disminuía el riesgo de DH (OR 0,093, IC 95% 0,009 a 0,959, p = 0,046), mientras que alguna enfermedad subyacente aumentaba el riesgo (OR 6,34, IC 95% 1,009 a 39,89, p = 0,049). Conclusiones: la presencia de desnutrición y antecedentes patológicos previo al ingreso fueron factores de riesgo para presentar DH.

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Research on human subjects cannot occur if it does not comply with these ethical principles: autonomy, beneficence and justice. The historical antecedents that emphasized the need to have documents to guide the researchers' behavior point to regrettable events for humanity. Even though the first recommendations were published more than 50 years ago in the Declaration of Helsinki, it is possible to find examples of investigations that have been conducted without complying with the aforementioned ethical principles. Approval by an ethics committee is required by law for all the research projects that involve human subjects. At present, virtually all scientific journals require the proof of approval and they assess whether the risks which participants were subjected to in the studies were necessary, and they also assess whether the benefits that were obtained from the research justify its conduction. Meeting the criteria that are required in order to conduct a study in an ethical manner should not be seen as an imposition; but as a moral commitment that has been established between the researcher and the participants of the study.

La investigación en seres humanos no puede llevarse a cabo sin cumplir con los principios éticos de autonomía, beneficencia y justicia. Los antecedentes históricos que destacaron la necesidad de contar con documentos para guiar la conducta de los investigadores señalan hechos lamentables para la humanidad. Aun cuando desde hace más de 50 años se publicaron las primeras recomendaciones en la Declaración de Helsinki, se pueden encontrar ejemplos de investigaciones que se han llevado a cabo sin respetar dichos principios. La aprobación por un comité de ética es un requisito de ley para todas las investigaciones en seres humanos. En la actualidad, prácticamente todas las revistas científicas solicitan el comprobante de la aprobación y evalúan si los riesgos a los que se sometieron los participantes de los estudios eran necesarios y los beneficios obtenidos de la investigación justificaron su realización. Cumplir con los requisitos que se solicitan para conducir éticamente un estudio no debe considerarse como una imposición, sino como un compromiso moral que se establece entre el investigador y los participantes del estudio.

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