Abstract
Sputum examination can be useful in diagnosing the cause of pneumonia in adults but is less well established in children. We sought to assess the diagnostic utility of polymerase chain reaction (PCR) for detection of respiratory viruses and bacteria in induced sputum (IS) specimens from children hospitalized with severe or very severe pneumonia. Among children aged 1-59 months, we compared organism detection by multiplex PCR in IS and nasopharyngeal/oropharyngeal (NP/OP) specimens. To assess whether organism presence or density in IS specimens was associated with chest radiographic evidence of pneumonia (radiographic pneumonia), we compared prevalence and density in IS specimens from children with radiographic pneumonia and children with suspected pneumonia but without chest radiographic changes or clinical or laboratory findings suggestive of pneumonia (nonpneumonia group). Among 4232 cases with World Health Organization-defined severe or very severe pneumonia, we identified 1935 (45.7%) with radiographic pneumonia and 573 (13.5%) with nonpneumonia. The organism detection yield was marginally improved with IS specimens (96.2% vs 92.4% for NP/OP specimens for all viruses combined [P = .41]; 96.9% vs 93.3% for all bacteria combined [P = .01]). After accounting for presence in NP/OP specimens, no organism was detected more frequently in the IS specimens from the radiographic pneumonia compared with the nonpneumonia cases. Among high-quality IS specimens, there were no statistically significant differences in organism density, except with cytomegalovirus, for which there was a higher quantity in the IS specimens from cases with radiographic pneumonia compared with the nonpneumonia cases (median cycle threshold value, 27.9 vs 28.5, respectively; P = .01). Using advanced molecular methods with IS specimens provided little additional diagnostic information beyond that obtained with NP/OP swab specimens.
Highlights
Sputum examination can be useful in diagnosing the cause of pneumonia in adults but is less well established in children
The World Health Organization (WHO) recommends empiric treatment for community-acquired pneumonia (CAP) in children [1], determining the causative pathogen is important if empiric therapy fails and important at a population level to guide treatment and prevention strategies
There is less experience using sputum specimens in children for etiologic diagnosis because of the challenges posed by contamination with upper respiratory tract secretions and frequent colonization of the upper respiratory tract with known respiratory pathogens, such as pneumococcus [7, 8]
Summary
Among children aged 1–59 months, we compared organism detection by multiplex PCR in IS and nasopharyngeal/oropharyngeal (NP/OP) specimens. The PERCH study sought to determine the cause of severe pneumonia in children aged 1–59 months living in developing areas [21]. IS specimen collection was attempted within 24 hours of hospital admission for each PERCH case unless contraindicated. We defined 2 subsets of PERCH cases: (1) children with radiographic evidence of pneumonia defined by the presence of consolidation and/or other infiltrate on chest radiographs, representing children who truly had infectious pneumonia, and (2) children with clinical and laboratory characteristics highly indicative of the absence of pneumonia, representing children enrolled into the case arm but with a very low likelihood of having infectious pneumonia (ie, nonpneumonia group; Text Box 1). Because IS specimens were not collected from controls, the nonpneumonia cases acted as “mock controls,” and this group was compared for similarity with PERCH control children
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