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ResumenSe comparan los métodos de remuestreo Bootstrap-t y Jackknife delete I y delete II, utilizando los estimadores no paramétricos de Kaplan-Meier y Nelson-Aalen, que se utilizan con frecuencia en la práctica, teniendo en cuenta diferentes porcentajes de censura, tamaños de muestra y tiempos de interés. La comparación se realiza vía simulación, mediante el error cuadrático medio.Palabras clave: Bootstrap, Jackknife, Función de confiabilidad. AbstractIn this paper the resampling methods bootstrap-t, Jackknife delete I and delete II, are compared using the nonparametric estimators Kaplan-Meier and Nelson-Aalen, frequently used in the practice, taking into account different percentages of censorship, sample sizes and times of interest. The comparation is carried out by simulation, using the mean square error.

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The guideline is intended for use by healthcare providers who care for adult and pediatric patients with group A streptococcal pharyngitis. The guideline updates the 2002 Infectious Diseases Society of America guideline and discusses diagnosis and management, and recommendations are provided regarding antibiotic choices and dosing. Penicillin or amoxicillin remain the treatments of choice, and recommendations are made for the penicillin-allergic patient, which now include clindamycin.

There is concern that group A streptococci, which have caused less serious infections in developed countries in recent decades, may be acquiring greater virulence. We describe 20 patients from the Rocky Mountain region who had group A streptococcal infections from 1986 to 1988 that were remarkable for the severity of local tissue destruction and life-threatening systemic toxicity. Among the 20 patients (median age, 36), necrotizing fasciitis with or without myositis was the most common soft-tissue infection (55 percent). Nineteen patients (95 percent) had shock, 16 (80 percent) had renal impairment, and 11 (55 percent) had acute respiratory distress syndrome. The mortality rate was 30 percent. All patients but 1 had positive tissue cultures for Streptococcus pyogenes; 12 had positive blood cultures. Most of the patients had no underlying disease; 2 used intravenous drugs. Strains of group A beta-hemolytic streptococci isolated from 10 patients were not of a single M or T type; however, 8 of the 10 strains produced pyrogenic exotoxin A (scarlet fever toxin A, a classic erythrogenic toxin), which has rarely been observed in recent years. From our study of this cluster of severe streptococcal infections with a toxic shock-like syndrome, we conclude that in our region, more virulent group A streptococci have reappeared that produce the pyrogenic toxin A associated with scarlet fever.

This revision of the Jones criteria now brings them into closer alignment with other international guidelines for the diagnosis of acute rheumatic fever by defining high-risk populations, recognizing variability in clinical presentation in these high-risk populations, and including Doppler echocardiography as a tool to diagnose cardiac involvement.

The objective of this practice guideline is to provide recommendations for the accurate diagnosis and optimal treatment of group A streptococcal pharyngitis in children and adults. The desired outcomes are prevention of acute rheumatic fever, prevention of suppurative complications, improvement of clinical symptoms and signs, reduction in transmission of group A bhemolytic streptococci to close contacts of patients, and minimization of potential adverse effects of inappropriate antimicrobial therapy. This statement is an update of the practice guideline published in 1997 [1] and takes into account relevant research published since that time. A major substantive change is the acceptance of negative results of rapid antigen detection testing (RADT) for exclusion of acute streptococcal pharyngitis, without the previously mandated confirmation with a negative culture result, provided certain criteria are met, as detailed below. Diagnosis. Acute pharyngitis is one of the most frequent illnesses for which pediatricians, internists, and other primary care physicians are consulted. Although the group A streptococcus is the most common