Alonso Soto

Observational studies are an important source of information in clinical epidemiology, but sample size calculation often poses difficulties during research planning. This calculation should be consistent with the study objective, study design, and effect measure of interest, as an inappropriate choice may lead to imprecise estimates or inefficient use of available resources. This methodological review presents the concepts and parameters required to estimate sample size or, when appropriate, statistical power in descriptive and analytical observational studies, including cross-sectional, case-control, and cohort designs. Alpha and beta errors, precision, confidence level, baseline outcome frequency, expected effect size, and selection of the association measure according to study design are reviewed. Considerations for finite populations, adjustments for loss to follow-up or incomplete data, and scenarios in which the number of observations is predetermined are also described; in such cases, statistical power or the minimum detectable effect may be assessed. Finally, recommendations are provided for documenting sample size calculations in research protocols and for selecting statistical tools according to the characteristics of the study.

The training of medical specialists constitutes one of the fundamental pillars for ensuring the quality of modern health systems. In Peru, obtaining the title of specialist is linked to the National Medical Residency System, a model that integrates supervised clinical training, continuous evaluation, progressive clinical responsibilities, and academic certication under national standards. However, the recent debate generated (1)by the preliminary report on Bill No. 13,830/2025-CR, which proposes lato sensu training modalitiesand competency-basedcerticationasmechanismsequivalenttostructuredmedicalresidencyforthe recognition of medical specialties, has reopened a discussion that goes beyond the academic sphere and becomes a public health issue.

Deficiencies in primary care have drawn the attention of the public and the authorities in recent years. According to the Instituto Nacional de Estadística e Informática (INEI), through the Demographic and Family Health Survey (ENDES, by its Spanish acronym), low-income populations report lower health care-seeking behavior, not because they are healthier, but because of barriers to accessing the health system (1) . The challenges affecting primary health care are complex and must be addressed as soon as possible. However, it is equally true that hospital care requires urgent action in order to treat potentially life-threatening conditions that should be resolved promptly. The shortcomings of the hospital system may be reflected in high mortality rates, particularly in internal medicine wards (2) , where the complexity of care is not matched by the limited diagnostic and therapeutic support available.

Background: Clinical prediction rules integrate clinical and laboratory variables to estimate outcomes, facilitating decision-making and optimizing resources, especially in high-demand settings. We aimed to validate and compare the performance of four mortality prediction scores -ISARIC-4C, CALL, SEIMC, q-CSI- in a Peruvian cohort of unvaccinated hospitalized COVID-19 pneumonia patients during the initial pandemic wave. Methods: We performed a retrospective cohort study based on a secondary analysis of data from a previous study (March-December 2020). To ensure a robust and standardized head-to-head comparison, we utilized a complete-case analysis (n = 1,074). Selection bias was rigorously assessed by comparing the analytic sample with excluded patients. Each score’s performance was evaluated using sensitivity, specificity, predictive values, likelihood ratios, area under the receiver operating characteristic curve (AUROC), and robust calibration metrics, including the calibration intercept (α) and the calibration slope (β). The ISARIC-4C score was used as an international reference standard for benchmarking. Results: Among 3,074 hospitalized patients, 1,074 had complete data for all four scores; no clinically significant differences were found between this group and excluded participants, indicating a representative sample. The cohort was mainly male (67.9%) with a median age of 59 years. The q-CSI score showed the best discrimination (AUROC 0.85, 95% CI: 0.83–0.87), significantly better than ISARIC-4C (0.82, 95% CI: 0.80–0.85), SEIMC (0.78, 95% CI: 0.75–0.81), and CALL (0.69, 95% CI: 0.66–0.72) (p < 0.0001). Direct comparison favored q-CSI over ISARIC-4C (p = 0.0016). While the Hosmer-Lemeshow (HL) test indicated a lack of fit for some models, robust calibration analysis confirmed accurate scaling (β for all scores was approx. 1.0) and adequate centering (α values with p > 0.05), supporting their clinical reliability. Conclusions: In this Peruvian cohort, the q-CSI score exhibited the best predictive performance and highest feasibility for in-hospital mortality among patients with COVID-19 pneumonia. While the HL test indicated a lack of fit, the analysis of the calibration α and β confirmed that the models are globally well-calibrated, supporting their utility for risk stratification. However, local adjustment is still necessary prior to clinical use in our setting. These findings provide a valuable baseline for resource optimization in resource-limited setting during pandemic waves.

Lymphatic malformations (LM), such as giant cervical lymphangioma, are benign head and neck anomalies in childhood that are susceptible to serious complications such as superinfection. We present the case of a 3-year-old girl with a small right cervical mass since birth, which suddenly increased in size with pain, fever, and signs of inflammation. Examination revealed a soft, painful mass measuring 10 x 8 cm. CT confirmed a giant multicystic lesion (10.7 x 9.5 x 8.4 cm) in the right cervical region, displacing vital structures. The diagnosis was superinfected giant cervical lymphangioma. It was initially treated with antibiotics. Subsequently, complete surgical resection of the tumor (11.5 x 9 x 6 cm) was performed, preserving adjacent structures. Histopathology confirmed the diagnosis. The patient was discharged with a favorable outcome. The case highlights the need for timely evaluation and multidisciplinary management to treat acute exacerbations and ensure a positive prognosis.

Objective: To determine the influence of parents’ knowledge and attitudes on the administration of the human papillomavirus vaccine to their children in a public educational institution. Methods: cross-sectional, observational, and analytical study, with a representative sample of 125 parents of 4th and 5th grade primary school students in a public school in Peru. Sociodemographic data were collected, and structured questionnaires on knowledge and attitudes were administered. The data were analyzed using Poisson regression to calculate crude and adjusted prevalence ratios, along with their respective confidence intervals and p-values. Results: 125 participants were included, of which 41% reported having vaccinated their children against HPV. A high level of knowledge among parents was significantly associated with a higher likelihood of their children being vaccinated in the crude analysis (RPc = 2,24; 95 % CI: 1,17 – 4,32; p = 0,015), although after adjusting for age and sex, this association was not statistically significant (RPa = 1,90; 95 % CI: 0,98 – 3,66; p = 0,055). Positive attitudes towards vaccination showed a significant association with a higher likelihood of vaccination in both the crude analysis (RPc = 2,72; 95 % CI: 1,69 – 4,38; p < 0,001) and in the adjusted analysis (RPa = 2,55; 95 % CI: 1,58 – 4,13; p < 0,001). Conclusions: Positive parental attitudes towards vaccination significantly influence the frequency of human papillomavirus immunization in the studied school population. Keywords: Papillomavirus Vaccine, vaccination, parents (MESH).

La paracoccidioidomicosis es una micosis sistémica, endémica en Latinoamérica, causada por el hongo dimórfico Paracoccidioides spp., adquirido principalmente por la inhalación de esporas presentes en el ambiente. Afecta predominantemente a varones en áreas rurales debido a su exposición frecuente al suelo contaminado. Tras la infección primaria, el patógeno tiene el potencial de diseminarse por vía hematógena o linfática, comprometiendo diversos órganos y sistemas. La forma aguda de la paracoccidioidomicosis afecta la función de las células T periféricas y altera la maduración de los neutrófilos, mientras que la forma crónica se caracteriza por un deterioro progresivo de la respuesta inmune celular y un aumento en las citoquinas Th1. En casos severos, se pueden observar hipergammaglobulinemia, disminución de la capacidad fagocítica y desregulación inmunológica. Los factores de riesgo más importantes incluyen inmunosupresión previa y comorbilidades infecciosas, como coinfecciones por retrovirus. Presentamos el caso de un hombre de 68 años con paracoccidioidomicosis crónica diseminada y coinfección por HTLV-1. El paciente presentó lesiones mucocutáneas, compromiso pulmonar extenso y afectación suprarrenal significativa, evidenciándose la capacidad invasiva del Paracoccidioides spp. y el impacto adverso de la coinfección sobre la inmunidad. El paciente fue tratado inicialmente con anfotericina B; sin embargo, desarrolló falla multiorgánica, lo que conllevó a un desenlace fatal. Este caso destaca la necesidad de un enfoque integral para el diagnóstico y tratamiento de micosis diseminadas en pacientes inmunocomprometidos, especialmente en áreas endémicas. Asimismo, subraya la relevancia de considerar coinfecciones, como HTLV-1, que pueden modificar el curso clínico, empeorar el pronóstico y aumentar la mortalidad en estas patologías complejas.

Objectives: To determine the proportion of patients who achieved glycemic control within 24 hours of admission to the emergency department in three Peruvian hospitals, as well as to assess the relationship between the achievement of glycemic control at 24 hours and mortality and unfavorable outcomes. Methodology: An observational analytical cohort study was conducted in three Peruvian hospitals, including 730 patients admitted for hyperglycemia. Variables such as glycemic control, mortality, and unfavorable outcomes were examined using descriptive and multivariate statistical analyses. Results: The average age of the patients was 60 years, with a majority being male. 85.1% had a history of diabetes mellitus, and hypertension was the most prevalent comorbidity. 4% of patients died. Glycemic control was achieved in 45% of the patients. 34% received fixed doses of insulin. No association was found between glycemic control and mortality, the need for mechanical ventilation, or hemodialysis. Patients who achieved glycemic control had significantly shorter hospital stays compared to those who did not achieve control (51% vs. 60%; p=0.02). Conclusion: Glycemic control was achieved in 45% of patients admitted with hyperglycemia to the emergency department. The majority of patients received insulin in sliding scale regimens rather than fixed doses. Glycemic control within 24 hours was associated with a lower proportion of patients with prolonged hospital stays, although it was not associated with reduced mortality or the need for mechanical ventilation.