The utility of the WBC count to predict abnormal chest radiographs in febrile children from 90 days to 36 months of age

Abstract

Study objectives: The purpose of this study is to determine whether the WBC count is predictive of pneumonia on chest radiographs in children aged between 90 days and 36 months with a temperature of 103°F (39.4°C) or greater. Methods: This prospective study was conducted at an academic emergency department that treats 16,000 pediatric patients per year. Consecutive enrollment of subjects was performed by the principal investigator when the principal investigator was present. Patients were eligible if they were aged 3 to 36 months, had a rectal temperature of 103°F or greater, were immunocompetent, did not receive antibiotics before evaluation, and did not have otitis media or pneumonia on physical examination. Eligible patients were evaluated by physical examination, temperature, CBC count, blood culture, catheter-obtained urine analysis and culture, and chest radiography. All chest radiographs were interpreted by an attending pediatric radiologist. Sensitivity, specificity, predictive values, and likelihood ratios were calculated for WBC count, with a positive result at 10,000, 15,000, 20,000, and 25,000 cells/mL. Results: During a 17-month period, 125 patients were enrolled. Of these patients, 4 (3.2%) had an infiltrate on chest radiograph. The rate of a positive chest radiograph result increased with the WBC count as follows: WBC greater than 10,000 cells/mL, 4.9%; WBC greater than 15,000 cells/mL, 7.9%; WBC greater than 20,000 cells/mL, 13.3%; and WBC greater than 25,000 cells/mL, 20.0%. When the patients were divided according to their WBC count, 82 patients had a WBC greater than 10,000 cells/mL (sensitivity 100%, specificity 35%, likelihood ratio 1.55); 38 had a WBC greater than 15,000 cells/mL (sensitivity 75%, specificity 71%, likelihood ratio 2.59); 15 had a WBC greater than 20,000 cells/mL (sensitivity 50%, specificity 89%, likelihood ratio 4.65), and 10 had a WBC greater than 25,000 cells/mL (sensitivity 50%, specificity 93%, likelihood ratio 7.6). Conclusion: Although the prevalence of a positive chest radiograph result increases with an elevated WBC count, the sensitivity and specificity suggests it is a poor diagnostic test for prediction of pneumonia in pediatric patients. Study objectives: The purpose of this study is to determine whether the WBC count is predictive of pneumonia on chest radiographs in children aged between 90 days and 36 months with a temperature of 103°F (39.4°C) or greater. Methods: This prospective study was conducted at an academic emergency department that treats 16,000 pediatric patients per year. Consecutive enrollment of subjects was performed by the principal investigator when the principal investigator was present. Patients were eligible if they were aged 3 to 36 months, had a rectal temperature of 103°F or greater, were immunocompetent, did not receive antibiotics before evaluation, and did not have otitis media or pneumonia on physical examination. Eligible patients were evaluated by physical examination, temperature, CBC count, blood culture, catheter-obtained urine analysis and culture, and chest radiography. All chest radiographs were interpreted by an attending pediatric radiologist. Sensitivity, specificity, predictive values, and likelihood ratios were calculated for WBC count, with a positive result at 10,000, 15,000, 20,000, and 25,000 cells/mL. Results: During a 17-month period, 125 patients were enrolled. Of these patients, 4 (3.2%) had an infiltrate on chest radiograph. The rate of a positive chest radiograph result increased with the WBC count as follows: WBC greater than 10,000 cells/mL, 4.9%; WBC greater than 15,000 cells/mL, 7.9%; WBC greater than 20,000 cells/mL, 13.3%; and WBC greater than 25,000 cells/mL, 20.0%. When the patients were divided according to their WBC count, 82 patients had a WBC greater than 10,000 cells/mL (sensitivity 100%, specificity 35%, likelihood ratio 1.55); 38 had a WBC greater than 15,000 cells/mL (sensitivity 75%, specificity 71%, likelihood ratio 2.59); 15 had a WBC greater than 20,000 cells/mL (sensitivity 50%, specificity 89%, likelihood ratio 4.65), and 10 had a WBC greater than 25,000 cells/mL (sensitivity 50%, specificity 93%, likelihood ratio 7.6). Conclusion: Although the prevalence of a positive chest radiograph result increases with an elevated WBC count, the sensitivity and specificity suggests it is a poor diagnostic test for prediction of pneumonia in pediatric patients.