Use of sputum samples from children remains uncertain in CAP diagnosis

WASHINGTON — The clinical utility of induced sputum in children hospitalized with community-acquired pneumonia is unclear because even among children with good quality samples, the yield of pathogens was similar in children with and without pneumonia, according to findings presented here during the 2013 Pediatric Academic Societies Annual Meeting.

Researchers from the division of infectious diseases at St. Jude Children’s Research Hospital in Memphis, Tenn., found that children with community-acquired pneumonia (CAP) were able to provide sputa, but only 20% were good quality. In addition, pathogens isolated from sputa offered no better diagnostic indicator than children with positive or negative chest X-rays.

As part of the CDC Etiology of Pneumonia in the Community (EPIC) study, children aged 18 years or younger who were hospitalized with CAP were enrolled in the study based on clinical and radiographic criteria.

Children received nebulized albuterol and 7% saline to induce deep cough, and sputum was collected by expectoration or suction catheter. Sputa were considered good quality if the Gram’s stain had a white blood cell count of more than 25/low-power field with fewer than 10 epithelial cells/low-power field. Semi-quantitative bacterial culture was then performed, Amanda Anderson-Green, a medical student from the division of infectious diseases at St. Jude Children’s Research Hospital, and one of the study researchers, told Infectious Diseases in Children.

The dataset included 796 hospitalized children who provided sputa; 689 (86%) had CAP confirmed by the study radiologist and 107 did not. Of the 157 (20%) children who provided good quality sputa, 132 (19%) had pneumonia based on chest X-rays and 25 (23%) did not.

The proportion of sputa with one or more pathogens (Streptococcus pneumoniae, Haemophilus influenzae, methicillin-susceptible and methicillin-resistant Staphylococcus aureus, and Moraxella catarrhalis) detected was similar for children with and without pneumonia (49% vs. 48%).

Anderson-Green said children with good quality specimens had higher proportions of Streptococcus pneumoniae, Haemophilus influenzae, methicillin-susceptible and methicillin-resistant Staphylococcus aureus, and Moraxella catarrhalis detected than those with low-quality specimens (64% vs. 49%); however, this was true for children with and without pneumonia.

“When we compared the children with and without pneumonia they had similar proportions of pathogenic bacteria detected in their sputa,” Anderson-Green said.

She added, “It seems like bacteria may be detected whether or not you have pneumonia, and patients did not get better any faster if they received appropriate antibiotics for the bacteria detected. This study is limited because it is likely that bacteria that live in the upper airway were carried as the sputum passes through the oropharynx to be collected. Therefore, induced sputum as a diagnostic tool in its current form is not helpful in clinical decision making.”

For more information:

Anderson-Green AM. #2914.160. Presented at: Pediatric Academic Societies Annual Meeting; May 4-7, 2013; Washington.

Disclosure: Anderson-Green reports no relevant financial disclosures.