For decades, chest radiography (CXR) was considered to be the reference standard for diagnosis of community-acquired pneumonia (CAP). Studies of CAP diagnostics in children have used CXR as both a reference standard and an index test, with disagreement over how and when it should be used.1  Although frequently obtained, CXR has low sensitivity and only fair interrater reliability in diagnosing CAP.2  Radiography cannot differentiate bacterial from viral CAP and does not have substantial impact on outcomes.3  Furthermore, access to CXR is limited in many settings.

Given these limitations, the 2011 Pediatric Infectious Diseases Society and Infectious Diseases Society of America (PIDS/IDSA) pediatric CAP guideline recommends against routine CXR to confirm suspected CAP in children managed in the outpatient setting, a strong recommendation citing high-quality evidence.4  Despite this, among children 1 to 6 years of age managed as outpatients in the United States from 2008 to 2015, 83% of children with CAP received CXR in the emergency department (ED) compared with 22% in the primary care setting, with no change after guideline publication.5  This suggests that there is still room to improve, especially in the ED.

In this issue of Pediatrics, Geanacopoulos et al6  used the Pediatric Health Information System (PHIS), an administrative database, to evaluate CXR use in 30 pediatric EDs from 2008 to 2018 in children with a diagnosis of CAP, fever, or respiratory illness. CXR use has declined over time, from 30.4% to 18.6% in children with fever or respiratory illness and 86.6% to 80.4% in children with CAP, without an increase in revisit rates. That said, CXR use declined for all patients in EDs reporting data to PHIS, regardless of the diagnosis, and the time series analysis showed no association between PIDS/IDSA guideline publication and CXR rates. So this decline might not be specifically related to the evaluation of pneumonia. In addition, consistent with national data,5  this study reports that >80% of children with CAP are still receiving radiographs. It is thus not clear if the decline is clinically meaningful because the vast majority of children with CAP are still receiving CXRs in the ED.

In addition, the authors report declines in CAP diagnosis rates as the CXR rates decline. One potential conclusion put forth is that an increased reliance on history and examination was not associated with an increase in CAP diagnosis; however, one cannot discern how clinicians made their diagnostic decisions using PHIS. An alternative hypothesis is that the incidence of CAP is declining. In fact, the rate of pneumonia has been declining since implementation of the pneumococcal conjugate vaccine. In 8 French pediatric EDs, CAP rates declined from 6.3 cases per 1000 ED visits to 3.5 cases per 1000 ED visits with sustained reduction 7 years after 13-valent pneumococcal conjugate vaccine (PCV13) implementation.7  Similarly, in a study in Israel, researchers found an ∼45% decrease in alveolar CAP after PCV13 introduction.8  In the United States, hospitalization rates for pneumococcal pneumonia declined from 54 per 100 000 admissions to 23 per 100 000.9  The evolving epidemiology of CAP after PCV13 implementation is likely also responsible for the decline in CAP diagnoses found by Geanacopoulos et al.6 

The documented variation and high rate of CXR use, despite evidence suggesting that it does not change clinical outcomes or decisions in many cases, requires further attention. High rates of imaging likely reflect diagnostic uncertainty in pediatric CAP, concerns of missing a potentially serious infection, and a desire to limit antibiotic use if there is no evidence of radiographic CAP. The degree of variation in the Geanacopoulos study is large and consistent with previous studies, suggesting that higher-using hospitals have room to decrease their CXR use without impacting outcomes. Quality improvement initiatives have successfully decreased radiography in bronchiolitis and asthma and broad-spectrum antibiotic use in CAP.1012  Local and collaborative quality improvement efforts are one way to decrease CXR use in CAP, in addition to development of additional modalities to decrease diagnostic uncertainty.

There are 2 sides of the coin: imaging use and antibiotic use. This modest decline in CXR use in this study is encouraging, but the important question of whether this alters antibiotic use is still unknown. The authors conclude that decreased CXR use may not be associated with overdiagnosis of CAP. Unfortunately, this is a difficult conclusion to discern from this administrative data set, which does not capture discharge prescribing. CAP may still be overdiagnosed even if overall CXR use is down.

The question remains: do clinical signs and symptoms alone adequately diagnose children with CAP? Is a decline in CXR a good thing? In several studies, researchers have attempted to answer this question; however, in all of them, researchers use radiographic CAP as the reference standard. Most do not perform exceptionally well; none has been widely implemented into clinical practice, and no single sign or symptom is adequate for diagnosis.13  To add to this, most examination findings commonly used to diagnose clinical CAP are not terribly reliable, limiting their widespread use.14  With these limitations of clinical diagnosis, antibiotic misuse is an important consideration. In the same study of outpatient young children cited above, 70% to 80% received antibiotics (most broad spectrum) regardless of clinic or ED setting.5  This occurs despite evidence that most CAP in this age group is viral and despite PIDS/IDSA recommendations against routine antibiotic use in preschool children with CAP treated as outpatients.4 

Rates of pneumonia and CXR use are declining, and the study by Geanacopoulos et al6  confirms a promising trend documented by others. However, the definitive diagnosis of CAP remains elusive and limited by current reference standards. This study adds to a growing literature that improved diagnostics are necessary to answer several critical questions: Does this child have pneumonia? Does this child require antibiotics? Does this child need to be hospitalized? The growing interest in point-of-care diagnostic testing offers the potential for improving the accuracy and reliability of CAP pneumonia diagnosis and management. Until these newer modalities are fully evaluated, we will continue to struggle with the questions of how and when radiography should be used and what the best means are to guide antibiotic therapy in children with CAP.

Opinions expressed in these commentaries are those of the authors and not necessarily those of the American Academy of Pediatrics or its Committees.

FUNDING: No external funding.

COMPANION PAPER: A companion to this article can be found online at www.pediatrics.org/cgi/doi/10.1542/peds.2019-2816.

CAP

community-acquired pneumonia

CXR

chest radiography

ED

emergency department

PCV13

13-valent pneumococcal conjugate vaccine

PHIS

Pediatric Health Information System

PIDS/IDSA

Pediatric Infectious Diseases Society and Infectious Diseases Society of America

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Competing Interests

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.