Establishing Clinically Relevant Standards for Tachypnea in Febrile Children Younger Than 2 Years

Abstract

To determine values for defining tachypnea in febrile children younger than 2 years that best identify those at risk for pneumonia. Prospective case series. Children younger than 2 years presenting to the emergency department of a children's hospital with a temperature of 38 degrees C or higher. Using a standardized method, respiratory rates were obtained on eligible children for 1 year. Study patients were classified as having pneumonia or no pneumonia based on clinical evaluation and chest radiograph findings. Receiver operating characteristic curves were constructed to select the values for respiratory rate that maximized sensitivity and specificity of tachypnea as a sign of pneumonia. Data were analyzed for 572 children; pneumonia was present in 42 (7%). The diagnostic utility of tachypnea was maximal when cutoff values for respiratory rates of 59/min in infants younger than 6 months, 52/min in those aged 6 through 11 months, and 42/min in those aged 1 to 2 years were selected. Based on these definitions, tachypnea as a sign of pneumonia had a sensitivity of 73.8%, specificity of 76.8%, positive predictive value of 20.1%, and negative predictive value of 97.4%. Tachypnea, as defined in this study, is an important predictive sign of pneumonia in febrile children younger than 2 years. Conversely, the absence of tachypnea obviates the need for chest radiography in most settings.