Rapid noninvasive techniques for determining etiology of bronchitis and pneumonia in infants and children.

Table 2 lists the names, abbreviations, and principle underlying most of the rapid diagnostic techniques we have described. Table 3 lists the pathogens most likely to cause lower respiratory tract infections in pediatric patients, the specimens needed for each rapid diagnostic test now generally available, and the approximate time required for its actual performance. For maximal cost-effectiveness, it is recommended that laboratory diagnosis be pursued in a stepwise manner: 1) The usual patient with acute respiratory illness who is to be managed as an outpatient may need little if any laboratory evaluation. 2) For the child for whom hospital admission is being considered, serum C-reactive protein screen, urine bacterial antigen tests, and a cold agglutinin test (at the appropriate age) will help to classify the etiology of the infection as likely or unlikely to be bacterial. If antibiotic therapy is to be given, a blood culture should be obtained before starting. 3) For the child admitted to the hospital with a possible chlamydial or viral lower respiratory infection for whom specific therapy is considered, nasopharyngeal secretions should be examined for Chlamydia and for antigens of respiratory syncytial, parainfluenza, and influenza viruses to help select the appropriate antimicrobial. Serum for IgM level may be helpful. 4) For the child who has been intubated for respiratory support, a specimen of deep respiratory secretions should be sent for Gram stain, bacterial culture, for Chlamydia, and viral antigens and culture. 5) For patients presenting with atypical symptoms, signs, or clinical course additional diagnostic possibilities should be considered and appropriate tests done even if results may not be available within 48 hours.