Our study provides 4 main findings. We provide the first comprehensive national estimates of outpatient pediatric pneumonia. Second, the rate of outpatient pediatric CAP visits did not change significantly over a 14-year period, spanning the introduction of PCV7. Third, nonpenicillins were frequently prescribed for CAP, and macrolides remained the most commonly prescribed class of antibiotics for CAP over the 14-year study period. Fourth, increasing age, evaluation in the office setting when compared with the ED, and obtaining a radiograph or a CBC during the visit were associated with broad-spectrum antibiotic prescribing.
Outpatient CAP visit rates did not appreciably change over time despite licensure of PCV7 in 2000; Grijalva et al6
reported similar results in children under 6 years of age using data through 2003. There are several possible explanations. Radiographs confirming the CAP diagnosis were not routinely performed in the outpatient setting, which could lead to an overestimation of pneumonia rates. Clinical examination findings may have poor specificity for pneumonia diagnosis. In a randomized, double-blind study of PCV7 effectiveness, there was no difference in clinically diagnosed pneumonia incidence, but there was a 20% reduction in radiograph-confirmed pneumonia in PCV7 recipients compared with placebo recipients.22
Moreover, pneumococcal vaccination in adults is associated with reduced hospital mortality and length of stay for pneumonia.23
PCV7, therefore, may prevent severe pneumococcal CAP cases requiring hospitalization but may have minimal impact on the less severe CAP cases, which may or may not be caused by pneumococcus, diagnosed and managed in the outpatient setting. Our data did not demonstrate a decreasing proportion of CAP outpatients admitted; however, the surveys' intent is to capture a nationally representative sample of outpatient visits rather than inpatient admissions.
Nonpenicillins were frequently used for outpatient pediatric CAP, with macrolides being the most commonly prescribed class of antibiotics; additionally, cephalosporin use has increased since 2000. Dosing convenience and effective marketing of newer antibiotics may have made their use for outpatient infections increasingly appealing, yet current data suggest that penicillins remain appropriate first-line agents for pediatric CAP on the basis of their narrow spectrum of activity and known efficacy against the common bacterial causes of pneumonia.
We identified 4 factors strongly associated with the use of broad-spectrum antibiotics in the outpatient setting. Increasing age may be associated with increased broad-spectrum antibiotic use if providers are concerned about the higher prevalence of atypical pathogens such as Mycoplasma pneumoniae
among older children, although the efficacy of antibiotic therapy for pediatric Mycoplasma
pneumonia has not been conclusively shown.24–26
A preference for dosing convenience in older patients expected to manage their own medicines also may contribute to this finding.
Broad-spectrum antibiotic prescribing for CAP was more common in office settings than in the ED setting. This finding merits future study but is consistent with previous studies27,28
demonstrating decreased broad-spectrum antibiotic prescribing in the ED for acute otitis media and sore throat. Our data suggest that the increased use of broad-spectrum antibiotics in the office setting is not attributable to any individual class of broad-spectrum antibiotics. There may be increased exposure to pharmaceutical company representatives and samples in the office setting, creating a stimulus for the use of newer, better advertised, and typically broader-spectrum antibiotics. Treatment patterns in EDs also may be more standardized than they are in the office setting, with an increased use of institutional guidelines.
It is frequently impractical to perform radiographs as part of routine outpatient CAP diagnosis, and data suggest that performing radiographs may be associated with increased antibiotic use.29,30
Distinguishing atypical from viral pneumonia on chest radiograph can be difficult, which may have led providers to employ broad-spectrum antibiotics to include coverage for atypical pathogens. Obtaining a CBC may be a surrogate for disease severity in our outpatient population.
This study had several possible limitations. There is no unique ICD-9-CM code for CAP, so some misclassification of CAP patients may have occurred, although we minimized this possibility by using a previously validated ICD-9-CM diagnosis code algorithm for identifying patients with CAP.18
Likewise, we were unable to identify causative pathogens, and some patients diagnosed with CAP may have had viral etiologies. However, even with the understanding that some pneumonias in our cohort were likely viral, the misdiagnosis of viral pneumonias as bacterial should not have affected antibiotic selection once the physician's intent was to treat bacterial pneumonia.
Factors other than changing pneumococcal drug resistance may affect antibiotic choice. We attempted to account for these potential confounders in several ways. First, patients with chronic medical conditions were excluded, but our exclusion may have been incomplete, allowing some patients requiring broad-spectrum CAP therapy to remain in the study cohort. However, these patients would be more likely to receive care in the ED, and had any of these patients remained in the study it would cause us to underestimate the magnitude of broad-spectrum prescribing differences between offices and the ED. Second, specific covariates were examined for inclusion in our multivariable model to account for severity of illness. Our ability to adjust for illness severity was likely imperfect, but patients evaluated in the ED for CAP were likely more ill than those in office settings, again causing us to underestimate setting differences in broad-spectrum prescribing.
Finally, survey data have certain inherent limitations. Patient allergies are not available in either survey; antibiotic class allergies, although uncommon in general, might alter antimicrobial prescribing for CAP. The surveys also lack detailed clinical information such as symptoms or physical examination findings, which could help confirm the CAP diagnosis in patients identified using our algorithm.
Our study has several implications. The unchanged rate of outpatient pediatric CAP diagnosis despite introduction of PCV7 suggests that better diagnostics are needed to distinguish bacterial from viral pneumonia. Likewise, efforts to improve bacterial pneumonia diagnosis have the potential to decrease broad-spectrum antibiotic overuse significantly.