Tachypnea a Poor Predictor of Pneumonia in Children

Abstract

Tachypnea is included in the assessment of pneumonia in patients of all ages. The World Health Organization (WHO) has recommended the use of tachypnea in children as a proxy to the diagnosis of pneumonia in resource-poor settings. Previous studies report detecting more than 80% of children in the developing world who require antibiotic treatment of bacterial pneumonia using the WHO guidelines, however, the utility of using tachypnea to assess for pneumonia in a modern and readily accessible medical system is unclear. This prospective observational study sought to assess the association between tachypnea and pneumonia in a single academic pediatric emergency department in Boston. The study enrolled children younger than 5 years of age who underwent chest radiography (CXR) for evaluation of pneumonia. Tachypnea was defined using three measurements: mean triage respiratory rate (RR) by age group, age-defined tachypnea based on WHO guidelines (< 2 months [RR≥60 breaths/min], 2–12 months [RR≥50 breaths/min], 1–5 years [RR≥40 breaths/min]), and physician-assessed tachypnea based on clinical impression before CXR. Determination of pneumonia was based on the final CXR reading by an attending pediatric radiologist. Equivocal radiographs (e.g., atelectasis vs. pneumonia) were a priori defined as a CXR positive for pneumonia. A total of 1622 children were studied, of whom 235 (14.5%) had radiographic pneumonia. Sixty-two percent of patients were 1–5 years of age, whereas 32% were 2–12 months, and 6% were<2 months old. There was no difference in mean triage RR among children with pneumonia compared to those without (RR=39 breaths/min vs. RR=38 breaths/min, p=0.28). Using the WHO cutoffs, 20.4% of children with tachypnea had pneumonia, compared to 12.1% of children without tachypnea who had radiographic pneumonia (p<0.001). When physician assessment of tachypnea was reviewed, 17% of children had pneumonia and 13% of children with pneumonia did not have tachypnea (p=0.07). The positive predictive value (PPV) of the WHO criteria for identifying pneumonia among all age groups was 20.4%, compared with 16.7% with physician-assessed tachypnea. Multiple subgroup analyses were performed using different age groups, and although the PPV was slightly improved for the 1–5 years age group (25.5% using WHO vs. 21.2% using physician assessment), the PPV was never more than 30% for any age. A major limitation to note is that only 47% of eligible patients were enrolled (i.e., had a physician assessment of tachypnea performed), introducing significant bias into the study population. Another significant limitation is that children who were diagnosed with pneumonia on clinical grounds (e.g., fever and cough) who did not have a CXR performed were not included.