OBJECTIVES:

To assess the characteristics of children hospitalized with complicated pneumonia at US children’s hospitals and compare these characteristics with those of children hospitalized with community-acquired pneumonia (CAP).

METHODS:

We identified children hospitalized with complicated pneumonia (parapneumonic effusion, empyema, necrotizing pneumonia, or lung abscess) or CAP across 34 hospitals between 2011 and 2019. We evaluated differences in patient characteristics, antibiotic selection, and outcomes between children with complicated pneumonia and CAP. We, also, assessed seasonal variability in the frequency of these 2 conditions and evaluated the prevalence of complicated pneumonia over the 9-year study period.

RESULTS:

Compared with children hospitalized with CAP (n = 75 702), children hospitalized with complicated pneumonia (n = 6402) were older (a median age of 6.1 vs 3.4 years; P < .001), with 59.4% and 35.2% of patients ≥5 years of age, respectively. Patients with complicated pneumonia had higher rates of antibiotic therapy targeted against methicillin-resistant Staphylococcus aureus (46.3% vs 12.2%; P < .001) and Pseudomonas (8.6% vs 6.7%; P < .001), whereas differences in rates of coverage against mycoplasma were not clinically significant. Children with complicated pneumonia had a longer median hospital length of stay and higher rates of ICU admissions, mechanical ventilation, 30-day readmissions, and costs. Seasonal variation existed in both complicated pneumonia and CAP, with 42.7% and 46.0% of hospitalizations occurring during influenza season. The proportion of pneumonia hospitalizations due to complicated pneumonia increased over the study period (odds ratio 1.04, 95% confidence interval: 1.02–1.06).

CONCLUSIONS:

Complicated pneumonia more frequently occurs in older children and accounts for higher rates of resource use, compared to CAP.

Although the incidence of community-acquired pneumonia (CAP) has decreased over the past 2 decades,13  pneumonia remains the worldwide leading cause of mortality in postneonatal children younger than 5, accounting for 15% of all childhood deaths in 2017.4,5  A proportion of patients hospitalized with CAP are discharged with a diagnosis of complicated pneumonia, a broad term used to described a heterogenous group of pneumonia-related complications, including parapneumonic effusion, empyema, multilobar disease, cavitary abscess, necrotizing pneumonia, pneumothorax, and bronchopleural fistula.6,7  It is often proposed that various types of complicated pneumonia (ie, effusion and empyema) are different points along the same spectrum of disease in which pleural inflammation causes fluid collection and eventual tissue necrosis and liquification;8,9  however, there is a lack of consensus regarding the risk for progression from CAP to complicated pneumonia as well as the factors associated with the development of these complications. Furthermore, it remains unclear whether differences exist between complicated pneumonia and CAP, with respect to patient characteristics as well as course, treatment and outcomes among hospitalized children.

To address these gaps in knowledge, we used a large national database of US children’s hospitals to describe the epidemiology of complicated pneumonia in hospitalized children and compare patient and hospitalization characteristics of children with complicated pneumonia with those of children with CAP.

We conducted a cross-sectional study to assess the characteristics of children hospitalized with complicated pneumonia and compared these characteristics with those of children hospitalized with CAP. Data for this study were obtained from the Pediatric Health Information System (PHIS),10  an administrative database that contains inpatient, emergency department (ED), ambulatory surgery, and observation encounter-level data from >50 not-for-profit, tertiary care pediatric hospitals in the United States. These hospitals are affiliated with the Children’s Hospital Association (CHA) (Lenexa, KS). Data quality and reliability are assured through a joint effort between the CHA and participating hospitals. Portions of the data submission and data quality processes for the PHIS database are managed by IBM Corporation Watson Health (Ann Arbor, MI). For the purposes of external benchmarking, participating hospitals provide discharge and encounter data, including demographics, diagnoses, and procedures. Nearly all these hospitals also submit resource use data (eg, pharmaceuticals, imaging, and laboratory) into the PHIS. Data are deidentified at the time of data submission, and data are subjected to several reliability and validity checks before being included in the database.

We included children <19 years of age who presented to the ED and were admitted to either an inpatient or observation unit with a diagnosis of complicated pneumonia or CAP between July 1, 2011, and June 30, 2019. After excluding hospitals without continuous data from 2011 to 2019 and hospitals with data quality issues around ED linkage to hospitalization, 34 PHIS participating children’s hospitals were included in our study. A patient was considered to have the diagnosis of complicated pneumonia if they met one of the following criteria: (1) a primary discharge diagnosis of complicated pneumonia, (2) primary discharge diagnosis of CAP in a patient who underwent a pleural drainage procedure during the hospitalization, or (3) primary discharge diagnosis of CAP with a secondary diagnosis of complicated pneumonia. We defined complicated pneumonia using a previously validated set of International Classification of Diseases, Ninth Revision, (ICD-9) diagnoses codes11  (empyema with fistula [510.0], empyema without fistula [510.9], pleurisy without effusion [511.0], pleurisy with effusion [511.1], unspecified pleural effusion [511.9], and abscess of lung [513.0]), and we translated the codes to equivalent International Classification of Diseases, 10th Revision, (ICD-10) codes using General Equivalence Mapping files published by Centers for Medicare and Medicaid Services12  (Supplemental Table 4). We defined CAP using a previously validated set of ICD-9 diagnoses codes11  and ICD-10 equivalents. To be included in the CAP group, patients required a primary diagnosis code of CAP, excluding patients with complicated pneumonia. Pleural drainage procedures were defined by ICD-9 procedure codes for thoracentesis (34.04), video-assisted thoracoscopic surgery (34.21), and thoracotomy (34.02 and 34.09),13  and ICD-10 equivalents. We excluded patients who were hospitalized within 30 days before the index visit as well as patients transferred from another institution because of an inability to ascertain diagnostic testing and treatment occurring before transfer.

Demographic characteristics included age (0–30 days, 31–365 days, 1–4 years, 5–12 years, or 13–18 years), sex, race and ethnicity, and insurance type (private versus public). Patients were classified as having complex chronic conditions by using a validated set of ICD-9 and ICD-10 diagnostic and procedure codes, which includes diagnoses that are (1) expected to last >12 months and (2) involve either several organ systems or 1 organ system severely enough to require specialty and care and hospitalization.14,15 

Laboratory testing included serum studies (complete blood count, blood gas, C-reactive protein, procalcitonin, erythrocyte sedimentation rate, and blood culture), viral studies, and respiratory culture evaluation. Treatment variables included antibiotic administration (categorized into the following classes: cephalosporins, penicillins and aminopenicillins, macrolides, ampicillin and sulbactam, clindamycin, vancomycin, piperacillin and tazobactam, fluoroquinolone, sulfamethoxazole and trimethoprim, and other), antibiotics conferring antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas and Mycoplasma, and corticosteroid administration. Only medications administered on the initial or second hospital day were included.

We also measured the duration of hospitalization (1–2, 3–7, or >7 days), receipt of ICU care, extracorporeal membrane oxygenation (ECMO) or mechanical ventilation, death during hospitalization, and all-cause readmission within 30 days of hospitalization; we stratified these outcomes by age group (0–4 years of age and 5–18 years of age). We also compared patients who met the criteria for complicated pneumonia on the basis of a diagnosis code for simple parapneumonic effusion to children with other complicated pneumonia diagnoses (ie, empyema, cavitary abscess, etc). Hospitalization costs were calculated by using the ratio of cost to charges submitted by the hospitals on their respective Medicare cost reports. Costs were adjusted by using the Centers for Medicare and Medicaid Services wage and price index for the hospital’s location and adjusted for inflation to 2019 dollars by using the annual Consumer Price Index inflation rate for the “hospital and related services” expenditure category.16 

Hospital and patient-level characteristics were stratified by pneumonia type and summarized by using frequencies and percentages or median and interquartile range (IQR) for categorical and continuous variables, respectively.

To evaluate differences between complicated pneumonia and CAP, we compared patient and hospitalization characteristics, resource use, testing, and treatments between groups using χ2 tests and median differences for categorical and continuous outcomes, respectively. The analysis of corticosteroid administration was stratified by asthma codiagnosis.

We, additionally, assessed seasonal variability in the frequency of these 2 conditions, and evaluated the proportion of hospitalizations that occurred during influenza season (December 1 through March 31).17 

We estimated a logistic regression model to evaluate the prevalence of a complicated pneumonia diagnosis over time, with the pneumonia type as the dependent variable and academic year as the independent variable, using robust SE clustered on hospital to account for intrahospital correlation among patients. All analyses were performed by using Stata version 16.0 (Stata Corp, College Station, TX). All statistical tests were 2 tailed, and α was set at .05. This study was approved by both our hospital’s institutional review board and the CHA.

After excluding hospitalizations in which a patient was transferred from a different institution (n = 11 533) and in which a patient had been hospitalized within the previous 30-day window (n = 7269), there were 82 104 children included over the study period: 6402 with complicated pneumonia and 75 702 with CAP (Supplemental Fig 3). Across hospitals, the median proportion of all pneumonia hospitalizations due to complicated pneumonia was 8.4% (IQR: 7.2%–9.6%; Fig 1). In 7 hospitals, >10% of all pneumonia hospitalizations were for complicated pneumonia. The proportion of pneumonia hospitalizations due to complicated pneumonia increased over the 9-year study period (test for linear trend: odds ratio 1.04, 95% confidence interval: 1.02–1.06). Although the total number of cases of complicated pneumonia per year remained relatively stable over the study period, the total number of cases of CAP decreased by 17.5% from 2011 to 2018, and, thus, the proportion of cases of complicated pneumonia increased from 7.5% in 2011 to 8.8% in 2018 (Supplemental Table 5).

FIGURE 1

Hospital-level variation in the prevalence of complicated pneumonia and CAP.

FIGURE 1

Hospital-level variation in the prevalence of complicated pneumonia and CAP.

Close modal

Compared with children with CAP, children hospitalized with complicated pneumonia were older (median age of 6.1 vs 3.4 years; P < .001), with 59.4% and 35.2% of patients ≥5 years of age, respectively (Table 1). Seasonal variation existed in both complicated pneumonia and CAP, with 42.7% and 46.0% of hospitalizations occurring during influenza season, respectively (Fig 2). Rates of microbiologic testing and inflammatory markers were higher among children with complicated pneumonia compared with those with CAP, whereas rates of viral testing were lower (Supplemental Fig 4).

TABLE 1

Patient Characteristics of Children With Complicated Pneumonia and CAP

CharacteristicComplicated Pneumonia (n = 6402)CAP (n = 75 702)P
Age, n (%)   <.001 
 0–30 d 7 (0.1) 288 (0.4) — 
 31–364 d 408 (6.4) 9509 (12.6) — 
 1–4 y 2187 (34.1) 39 221 (51.8) — 
 5–12 y 2675 (41.8) 21 211 (28.0) — 
 13–18 y 1125 (17.6) 5473 (7.2) — 
Median age (IQR), y 6.1 (3.2–10.9) 3.4 (1.7–6.5) <.001 
Female, n (%) 2928 (45.7) 35 931 (47.5) .008 
Race, n (%)   <.001 
 White 3692 (57.7) 41 231 (54.5) — 
 Black 1232 (19.2) 16 003 (21.1) — 
 Asian American 267 (4.2) 2726 (3.6) — 
 Other 884 (13.8) 11 956 (15.8) — 
 Missing 327 (5.1) 3786 (5.0) — 
Ethnicity   <.001 
 Hispanic 1465 (22.9) 18 731 (24.7) — 
 Not Hispanic 4574 (71.5) 52 304 (69.1) — 
 Unknown 363 (5.7) 4667 (6.2) — 
Primary payment source   <.001 
 Private 2638 (41.2) 26 842 (35.5) — 
 Public 3356 (52.4) 45 119 (59.6) — 
 Other 239 (3.7) 2450 (3.2) — 
 Missing 169 (2.6) 1291 (1.7) — 
Complex chronic condition 2093 (32.7) 22 730 (30.0) <.001 
Hospital region   <.001 
 Northeast 708 (11.1) 9350 (12.3) — 
 South 2791 (43.6) 31 790 (42.0) — 
 Midwest 1230 (19.2) 15 520 (20.5) — 
 West 1673 (26.1) 19 042 (25.2) — 
CharacteristicComplicated Pneumonia (n = 6402)CAP (n = 75 702)P
Age, n (%)   <.001 
 0–30 d 7 (0.1) 288 (0.4) — 
 31–364 d 408 (6.4) 9509 (12.6) — 
 1–4 y 2187 (34.1) 39 221 (51.8) — 
 5–12 y 2675 (41.8) 21 211 (28.0) — 
 13–18 y 1125 (17.6) 5473 (7.2) — 
Median age (IQR), y 6.1 (3.2–10.9) 3.4 (1.7–6.5) <.001 
Female, n (%) 2928 (45.7) 35 931 (47.5) .008 
Race, n (%)   <.001 
 White 3692 (57.7) 41 231 (54.5) — 
 Black 1232 (19.2) 16 003 (21.1) — 
 Asian American 267 (4.2) 2726 (3.6) — 
 Other 884 (13.8) 11 956 (15.8) — 
 Missing 327 (5.1) 3786 (5.0) — 
Ethnicity   <.001 
 Hispanic 1465 (22.9) 18 731 (24.7) — 
 Not Hispanic 4574 (71.5) 52 304 (69.1) — 
 Unknown 363 (5.7) 4667 (6.2) — 
Primary payment source   <.001 
 Private 2638 (41.2) 26 842 (35.5) — 
 Public 3356 (52.4) 45 119 (59.6) — 
 Other 239 (3.7) 2450 (3.2) — 
 Missing 169 (2.6) 1291 (1.7) — 
Complex chronic condition 2093 (32.7) 22 730 (30.0) <.001 
Hospital region   <.001 
 Northeast 708 (11.1) 9350 (12.3) — 
 South 2791 (43.6) 31 790 (42.0) — 
 Midwest 1230 (19.2) 15 520 (20.5) — 
 West 1673 (26.1) 19 042 (25.2) — 

—, not applicable.

FIGURE 2

Seasonal variability in hospitalizations for complicated pneumonia and CAP. Influenza season is shaded gray (December 1 through March 31).

FIGURE 2

Seasonal variability in hospitalizations for complicated pneumonia and CAP. Influenza season is shaded gray (December 1 through March 31).

Close modal

Antibiotic prescribing patterns differed between children hospitalized with complicated pneumonia and those with CAP. Cephalosporins were administered to 74.3% of children with complicated pneumonia compared with 50.8% of children with CAP (P < .001), whereas penicillins were prescribed less frequently among children with complicated pneumonia, compared with children with CAP (26.0% vs 40.6%; P < .001; Table 2). When compared with patients with CAP, patients with complicated pneumonia had higher rates of antibiotic therapy targeted against MRSA (46.3% vs 12.2%; P < .001) and Pseudomonas (8.6% vs 6.7%; P < .001), whereas differences in rates of coverage against mycoplasma were not clinically significant (25.2% vs 23.9%; P = .02). Furthermore, children hospitalized with complicated pneumonia were less likely than those with CAP to receive corticosteroids as adjunctive treatment (17.0% vs 34.4%; P < .001%), which was consistent among children with and without an asthma codiagnosis.

TABLE 2

Antibiotic and Corticosteroid Administration in Children With Complicated Pneumonia and CAP

Medication AdministrationComplicated Pneumonia(n = 6402), n (%)CAP(n = 75 702), n (%)P
Individual antibiotic    
 Cephalosporin 4755 (74.3) 38 426 (50.8) <.001 
 Penicillin and aminopenicillins 1666 (26.0) 30 713 (40.6) <.001 
 Macrolides 1469 (23.0) 16 977 (22.4) .339 
 Ampicillin and sulbactam 354 (5.5) 4775 (6.3) .014 
 Clindamycin 1876 (29.3) 4701 (6.2) <.001 
 Vancomycin 1376 (21.5) 3923 (5.2) <.001 
 Piperacillin and tazobactam 180 (2.8) 1449 (1.9) <.001 
 Fluoroquinolone 158 (2.5) 1265 (1.7) <.001 
 Sulfamethoxazole and trimethoprim 97 (1.5) 1015 (1.3) .246 
 Other 171 (2.7) 1433 (1.9) <.001 
Antibiotic coveragea    
 MRSA coverage 2966 (46.3) 9232 (12.2) <.001 
 Pseudomonal coverage 552 (8.6) 5041 (6.7) <.001 
Mycoplasma coverage 1615 (25.2) 18 115 (23.9) .020 
Corticosteroidsb 1091 (17.0) 26 039 (34.4) <.001 
 Codiagnosis of asthmac 598 (9.3) 16 718 (22.1) <.001 
 No codiagnosis of asthma 439 (6.9) 9321 (12.3) <.001 
Medication AdministrationComplicated Pneumonia(n = 6402), n (%)CAP(n = 75 702), n (%)P
Individual antibiotic    
 Cephalosporin 4755 (74.3) 38 426 (50.8) <.001 
 Penicillin and aminopenicillins 1666 (26.0) 30 713 (40.6) <.001 
 Macrolides 1469 (23.0) 16 977 (22.4) .339 
 Ampicillin and sulbactam 354 (5.5) 4775 (6.3) .014 
 Clindamycin 1876 (29.3) 4701 (6.2) <.001 
 Vancomycin 1376 (21.5) 3923 (5.2) <.001 
 Piperacillin and tazobactam 180 (2.8) 1449 (1.9) <.001 
 Fluoroquinolone 158 (2.5) 1265 (1.7) <.001 
 Sulfamethoxazole and trimethoprim 97 (1.5) 1015 (1.3) .246 
 Other 171 (2.7) 1433 (1.9) <.001 
Antibiotic coveragea    
 MRSA coverage 2966 (46.3) 9232 (12.2) <.001 
 Pseudomonal coverage 552 (8.6) 5041 (6.7) <.001 
Mycoplasma coverage 1615 (25.2) 18 115 (23.9) .020 
Corticosteroidsb 1091 (17.0) 26 039 (34.4) <.001 
 Codiagnosis of asthmac 598 (9.3) 16 718 (22.1) <.001 
 No codiagnosis of asthma 439 (6.9) 9321 (12.3) <.001 

MRSA coverage: vancomycin, linezolid, clindamycin, daptomycin, ceftaroline, sulfamethoxazole and trimethoprim, doxycycline, and minocycline. Pseudomonal coverage: ceftazidime, cefepime, levofloxacin, ciprofloxacin, meropenem, ertapenem, imipenem, gentamicin, amikacin, aztreonam, and piperacillin and tazobactam. Mycoplasma coverage: erythromycin, azithromycin, clarithromycin, doxycycline, minocycline, levofloxacin, ciprofloxacin, and moxifloxacin. Included medications: dexamethasone, methylprednisolone, prednisolone, prednisone, betamethasone, triamcinolone, and hydrocortisone.

a

Antibiotics: limited to those prescribed on initial or second day of hospitalization and those administered via enteral, intravenous, or intramuscular route.

b

Corticosteroids: limited to those prescribed on initial or second day of hospitalization and those administered via enteral, intravenous, or intramuscular route.

c

Diagnosis of asthma: ICD 9: 493.00–493.92; ICD 10: J45.20–J45.998.

Median hospital length of stay was longer for children with complicated pneumonia than those with CAP (4 vs 2 days; P < .001; Table 3), and a higher proportion of children with complicated pneumonia were hospitalized for >7 days, compared with children with CAP (31.6% vs 6.3%; P < .001). Children with complicated pneumonia also more frequently required ICU care (23.6% vs 12.1%; P < .001) and mechanical ventilation (12.0% vs 5.5%; P < .001). Rates of 30-day readmission were higher in patients with complicated pneumonia, compared with those with CAP (8.2% vs 6.4%; P < .0001), as was the median cost of hospitalization ($14 432 vs $6720; P < .001). These findings remained significant in the age-stratified analysis (Supplemental Table 6). Compared with other children with complicated pneumonia, the subset of children with simple parapneumonic effusions had shorter hospitalizations, lower rates of ICU hospitalization and mechanical ventilation, and lower costs (Supplemental Table 7).

TABLE 3

Hospitalization Characteristics of Children Admitted With Complicated Pneumonia and CAP

CharacteristicComplicated Pneumonia (n = 6402)CAP (n = 75 702)P
Hospital length of stay, n (%)   <.001 
 1–2 d 1959 (30.6) 47 443 (62.7) — 
 3–7 d 2418 (37.8) 23 481 (31.0) — 
 >7 d 2025 (31.6) 4778 (6.3) — 
Median length of stay (IQR), d 4 (2–9) 2 (1–3) <.001 
ICU care received, n (%) 1508 (23.6) 9137 (12.1) <.001 
ECMO, n (%) 16 (0.25) 22 (0.03) <.001 
Mechanical ventilation, n (%) 770 (12.0) 4181 (5.5) <.001 
Death, n (%) 38 (0.6) 113 (0.2) <.001 
Readmission within 30 d, n (%)    
 For any reason 525 (8.2) 4836 (6.4) <.001 
 For CAP and/or complicated pneumonia 355 (5.6) 2008 (2.7) <.001 
 For complicated pneumonia 353 (5.5) 238 (0.3) <.001 
Median hospitalization cost (IQR), $ 14 432 (6768–32 493) 6720 (4268–11 667) <.001 
CharacteristicComplicated Pneumonia (n = 6402)CAP (n = 75 702)P
Hospital length of stay, n (%)   <.001 
 1–2 d 1959 (30.6) 47 443 (62.7) — 
 3–7 d 2418 (37.8) 23 481 (31.0) — 
 >7 d 2025 (31.6) 4778 (6.3) — 
Median length of stay (IQR), d 4 (2–9) 2 (1–3) <.001 
ICU care received, n (%) 1508 (23.6) 9137 (12.1) <.001 
ECMO, n (%) 16 (0.25) 22 (0.03) <.001 
Mechanical ventilation, n (%) 770 (12.0) 4181 (5.5) <.001 
Death, n (%) 38 (0.6) 113 (0.2) <.001 
Readmission within 30 d, n (%)    
 For any reason 525 (8.2) 4836 (6.4) <.001 
 For CAP and/or complicated pneumonia 355 (5.6) 2008 (2.7) <.001 
 For complicated pneumonia 353 (5.5) 238 (0.3) <.001 
Median hospitalization cost (IQR), $ 14 432 (6768–32 493) 6720 (4268–11 667) <.001 

—, not applicable.

In this retrospective multicenter study of >80 000 children hospitalized with pneumonia, we found that children hospitalized with complicated pneumonia were older and had higher resource use, longer and more intensive hospitalizations, and higher 30-day readmission rates than children with CAP. Compared with children with CAP, children hospitalized with complicated pneumonia were more often treated with broader spectrum antibiotics targeting MRSA and Pseudomonas. We, also, observed that the proportion of pneumonia hospitalizations attributed to complicated pneumonia has been increasing over the past decade, now accounting for >8% of all pneumonia hospitalizations at US children’s hospitals.

Although other studies have revealed that the rate of both CAP and complicated pneumonia has decreased since the introduction of the pneumococcal conjugate vaccine 13 in 2010,2,3,18  we observed a decline in the rate of CAP hospitalizations and a relative increase in hospitalizations due to complicated pneumonia. Furthermore, we observed variation in the proportion of pneumonia hospitalizations attributed to complicated pneumonia across sites, ranging from 3.4% to 11.7%. Some of this variability may be attributed to regional differences in pneumococcal vaccination rates,19  environmental factors (including daily temperature trends),20  variation in susceptibility to developing more severe disease by region,21  or differing admission practices and referral patterns by site.22 

We observed that children hospitalized with complicated pneumonia were older than children hospitalized with CAP. This finding is consistent with a pneumococcal surveillance study across 8 hospitals, in which researchers found that patients with complicated disease were older (a median age of 43 months) than children with uncomplicated disease (a median age of 27 months).23  This distinct difference in age suggests that complicated pneumonia may not simply represent a progression of untreated or incompletely treated CAP but that particular host factors, such as waning immunity or other differences in host responses to infection by age,24  may alter a child’s risk for the development of complicated pneumonia. This also may explain why complicated pneumonia does not develop in all patients with untreated CAP.25  It is also possible that delays in care,26  decreased medication compliance,27  variance in infectious exposure,21  and a relatively higher proportion of bacterial (versus viral) pneumonia28  may account for higher rates of complicated pneumonia in older children.

Nearly one-half of all children hospitalized with complicated pneumonia receive antimicrobial coverage targeting MRSA within the first 2 days of hospitalization. In recent guidelines, targeted antimicrobial therapy for children hospitalized with pneumonia, guided by culture data when available, is recommended. Using administrative data, we are unable to determine if antibiotic usage among children with complicated pneumonia in our study was based on pathogen identification; however, in previous studies, researchers suggest the rate of performance of blood, sputum, and pleural fluid testing is relatively low among children, as is the yield of testing.2931  Furthermore, in cases of pathogen detection, identification of S aureus is relatively rare, detected in <10% of cases of complicated pneumonia.32  Given the high rate of antistaphylococcal agent usage among children with complicated pneumonia hospitalized at US children’s hospitals, further efforts are needed to allow for a targeted approach to the use of these agents.

We observed that the median hospitalization costs for complicated pneumonia were over double those for CAP, likely related to the longer duration of hospitalizations and more intensive treatment courses. It should be noted that nearly one-quarter of all complicated pneumonia hospitalizations required ICU level of care, and 12% required mechanical ventilation. It is, also, not surprising that the readmission rates were higher among children with complicated pneumonia, compared with those with CAP, but it is relatively reassuring that only 0.3% of children were readmitted for complicated pneumonia in the 30-day period after a hospitalization for CAP.

Our study has several limitations inherent to the use of administrative data. First, there is a lack of consensus on the definition of complicated pneumonia. In this study, we chose to use a previously validated set of ICD-9 codes for identification of complicated pneumonia;11  however, this definition is broad and inclusive, particularly related to whether a simple parapneumonic effusion constitutes complicated pneumonia. Over one-third (38.0%) of patients with complicated pneumonia met inclusion criteria for the study by having only a parapneumonic effusion diagnosis code, which likely explains why many patients in our study were hospitalized for ≤2 days. Second, the lack of clinical data limits our ability to correlate clinical findings with meaningful patient-level–outcomes. Additionally, the lack of culture data prohibits our ability to evaluate the appropriateness of antibiotic therapy. We, also, limited antibiotic exposure to medications received during the first 2 days of hospitalization and did not assess changes in antibiotic therapy occurring beyond 2 days. It is also important to note that our study was conducted among children cared for at freestanding children’s hospitals that serve as referral centers representing 15% of pediatrics hospitalizations. It is, therefore, likely that there is a disproportionately high prevalence of complicated pneumonia at the primarily tertiary and quaternary centers represented in this study, and, therefore, the prevalence of complicated pneumonia may be lower at community-based sites.

This is the largest study of children hospitalized with complicated pneumonia, which provides useful information to better understand differences in management and outcomes of children with complicated pneumonia and CAP. Compared with children with CAP, children with complicated pneumonia had longer and more costly hospitalizations and higher 30-day readmission rates. The variation in age distribution and geographic prevalence of complicated pneumonia highlights the need for further investigation into the pathogenesis and risk factors for development of complicated pneumonia in children.

Dr Gross conceptualized and designed the study, coordinated data collection, conducted the initial analyses, and drafted the initial manuscript; Mr Porter and Dr Monuteaux abstracted the data, conducted the initial analyses, and drafted the initial manuscript; Drs Lipsett and Hirsch contributed to the analyses; Dr Neuman conceptualized and designed the study, coordinated and supervised data collection, conducted the initial analyses, and drafted the initial manuscript; and all authors reviewed and revised the manuscript, approved the final manuscript as submitted, and agree to be accountable for all aspects of the work.

FUNDING: No external funding.

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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.

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