Community-acquired pneumonia in children

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Key Points

Pediatric community-acquired pneumonia (CAP) is an acute lower respiratory tract infection in a previously healthy child caused by an infection acquired outside of the hospital.[1][9] There is no reliable way clinically to distinguish between bacterial and viral etiology.[9] Most cases are caused by viruses, with respiratory syncytial virus (RSV) and human rhinovirus the most common etiologies.[4] Streptococcus pneumoniae is the most common typical bacterial pathogen.[4]
Symptoms are often fairly nonspecific but typically include fever, cough, tachypnea, and dyspnea. Hypoxemia is often found on pulse oximetry. Common signs on physical exam include increased work of breathing (e.g., chest retractions, nasal flaring, head bobbing) and decreased or abnormal breath sounds on auscultation (e.g., crackles, rales, crepitation, wheeze, rhonchi).[1][5][9][17]
In a previously healthy, immunocompetent child with nonsevere symptoms, CAP can be diagnosed clinically without the need for any blood tests, imaging, or microbiology tests.[1][9][18]
If a child has severe symptoms or suspected complications (e.g., pleural effusion, empyema, necrotizing pneumonia, lung abscess), arrange hospital admission for assessment and management.[1] Also consider hospital admission for any infant <6 months old.[1]
Chest x-ray and blood cultures are indicated for any child who is hospitalized for severe or complicated CAP.[1][3][9]

General principles

CAP is diagnosed clinically based on typical symptoms and signs, but these may vary with age and are often fairly nonspecific.[3][9] A careful history and thorough physical exam are needed to assess severity, identify any risk factors for disease progression, and look for any features that suggest complications (e.g., effusions, empyema).[3] CAP is a common condition in infants and children and is a frequent cause of hospital admission.[3]

History

Ask about the baseline health of the child and any underlying comorbidities, the duration and course of symptoms, exposure to sick contacts, immunization status, and recent travel history (as this may have a bearing on potential etiology and patterns of antibiotic resistance). In neonates, check for any maternal health issues or birth complications.

Symptom presentation

There is no universal presentation of CAP, and no single symptom or sign in isolation is sufficient to indicate CAP.[10] Consider the possibility of pneumonia if a child presents with a fever, particularly if associated with one or more of the following: tachypnea; chest crackles; nasal flaring; chest indrawing; cyanosis; oxygen saturation ≤95% on room air.[9][19]

One multicenter study covering 2358 children who had radiographic evidence of pneumonia found that 91% had fever.[4]

In addition to fever, other typical symptoms include:[1][9]

Rapid breathing. A raised respiratory rate compared with age-specific norms has been found to correlate well with hypoxemia.[20] Be aware, however, that some children with CAP have a normal respiratory rate.[9]
Cough. This is common but not always present, particularly in the early stages of illness.[3] It was present in 95% of children in a multicenter study of 2358 cases of radiographically confirmed CAP.[4]
Dyspnea or difficulty breathing. Some 70% of 2358 children with radiographic evidence of pneumonia had dyspnea.[4]
Wheeze. Wheeze on its own is a poor indicator of possible CAP and raises suspicion of an alternative diagnosis, such as viral wheeze or an exacerbation of asthma. The presence of wheeze has been found in several studies to be a negative predictor of radiographic CAP.[10][21][22] However, wheeze combined with other typical symptoms can be a pointer toward possible CAP. A study of 526 children evaluated for wheezing in the emergency department found only 4.9% had radiographically confirmed pneumonia.[23] However, when wheeze was accompanied by fever 6.9% were found to have radiographic evidence of pneumonia, and when wheeze, fever, and hypoxemia (oxygen saturation <92%) were all present, 20.6% of children had radiographic infiltrates.
Chest pain. This is more commonly reported in older children and adolescents.[5]

Other symptoms that may be present in some children are:

Abdominal pain. This is occasionally the predominant presenting symptom in children with CAP, especially among those <5 years old.[1]
Vomiting.[9]
Headache.[9]
Difficulty feeding, particularly in infants.
Agitation. This can sometimes be an indicator of hypoxemia.[9]

One systematic review of 23 prospective cohort studies involving a total of 13,833 children with suspected pneumonia concluded that no single symptom or sign reliably differentiates CAP from other childhood respiratory illnesses.[5]

Most but not all children presented with fever, cough, or both. However, hypoxemia and signs of increased work of breathing were found to be most strongly correlated with radiographic evidence of pneumonia.
The authors of the systematic review recommended checking oxygen saturation and carefully observing for evidence of increased work of breathing whenever a child presents with cough and/or fever.

Risk factors

Risk factors for CAP include:

Younger age. Children <2 years old are especially likely to develop CAP and especially complicated CAP (CCAP).[1][2][3] Age <5 years is a risk factor for severe CAP.[9]
Male sex. Boys have a higher incidence across all ages.[1][2][3][9]
Prematurity. Prematurity is one of the most important risk factors associated with respiratory diseases. CAP affects preterm infants at a higher rate than full-term infants.[1][2][3] Prematurity is also a risk factor for severe disease.[9]
Several chronic conditions. Among the long-term conditions associated with a higher risk of developing CAP, and particularly complicated CAP, are: immunodeficiency; malnutrition; chronic lung disease; congenital heart disease; neurodisability; cerebral palsy; cystic fibrosis; primary ciliary dyskinesia.[1][2][3][24]
A history of severe and/or complicated and/or recurrent pneumonia. This indicates a higher risk of progression to severe or complicated CAP in a child who presents with mild symptoms.[3]
Foreign body inhalation. An undiagnosed and retained inhaled foreign body is a risk factor for CAP and complicated CAP.[2]
Indoor air pollution, caused by cooking and heating with biomass fuels, such as wood or dung.[1][2][3]
Living in an overcrowded home. Data suggest that household crowding puts young children at increased risk of acute lower respiratory tract infection because it increases the rate of cross-infection among the family. Pathogens are easily and rapidly transmitted via air droplets and aerosols in crowded and poorly ventilated rooms where people are talking, sneezing, or coughing.[1][2][3]
Parental smoking. Children exposed to passive smoking have been found to have an increased likelihood of emergency department attendance and hospital admission for respiratory illness, although these data are not specific for CAP.[1][2][3]
An anatomic lesion. A vascular ring or sling (a type of congenital aortic arch anomaly) can result in compression of the trachea and predispose a child to recurrent lower respiratory tract infections.[13][14]

Etiology

There is no reliable way clinically to distinguish between bacterial and viral etiology.[9]

Most cases of CAP in infants, toddlers, and preschool children are caused by viruses. Respiratory syncytial virus (RSV) is the most common etiology, detected in 42% of hospitalized patients ages <2 years and 29% of those ages 2-4 years.[4] The other most commonly detected pathogens in hospitalized children in these age groups are human rhinovirus (29% and 25%, respectively) and human metapneumovirus (14% and 17%).[4]
In children ages 5-9 years, viral causes still predominate and human rhinovirus is the most frequent pathogen, detected in 30% of hospitalized cases.[4] Among those ages 10-17 years, viral etiologies remain more common than bacterial, with human rhinovirus identified in 19% of hospitalized patients.[4]
Bacterial pathogens make up a steadily increasing proportion of cases with increasing age. Streptococcus pneumoniae is the most common typical bacterial pathogen, detected in 4% of all children ages up to 17 years who are hospitalized for CAP.[4] However, atypical infection with Mycoplasma pneumoniae is the most frequent bacterial etiology, detected in 8% of all hospitalized patients (23% of those ages 10-17 years and 16% of those ages 5-9 years, compared with 5% of those ages 2-4 years and 2% of those <2 years).[4]

Consider bacterial CAP if the child has a persistent or repetitive fever >101.3°F (>38.5°C) together with chest recession and a raised respiratory rate.[9]

The reported incidence of mixed infections ranges from 8.2% to 23%. A prolonged fever in a child with influenza may indicate a secondary bacterial infection.[9]

There may be subtle differences in the presentation of CAP associated with specific pathogens.[9]

Pneumococcal pneumonia typically starts with fever and tachypnea. Cough is not an initial feature as alveoli have few cough receptors. Cough only begins after lysis occurs and debris irritates airway cough receptors.
Staphylococcal pneumonia is indistinguishable from pneumococcal pneumonia in the early stage of the disease.

Consider the possibility of atypical pneumonia based on local surveillance data.[17]

M pneumoniae infection tends to have peaks or outbreaks every 3-7 years.[25] Atypical pneumonia caused by M pneumoniae has been reported to account for 8% of CAP hospital admissions in the US.[4]
M pneumoniae classically has symptoms that are worse than signs would suggest. Presenting symptoms may be slowly progressing and often include cough that develops over 3-5 days, chest pain, low-grade fever, general malaise, and sometimes arthralgia, sore throat, and headache.[1][3][9][18] However, a Cochrane review of seven studies covering 1491 children in hospital settings found it is not possible to reliably diagnose pneumonia caused by M pneumoniae based on clinical symptoms and signs.[26]
For more detail, see Atypical pneumonia.

Physical exam

Conduct a thorough physical exam to look for signs that increase confidence in the clinical diagnosis of CAP or are suggestive of severe disease or complications.

Check in particular for hypoxemia (via pulse oximetry) and increased work of breathing (look for grunting; nasal flaring; subcostal, intercostal, or suprasternal chest retractions; and/or head bobbing).[1][9]

These two signs were the most specific indicators of radiographically confirmed CAP in a systematic review of 23 prospective studies involving 13,833 children with suspected pneumonia.[5]
Oxygen saturation ≤96% on pulse oximetry was found to have a likelihood ratio of 2.8 (95% CI 2.1 to 3.6), a sensitivity of 64%, and a specificity of 77% for pneumonia. Conversely, oxygen saturation >96% was a strong predictor that the child would not have radiographic evidence of pneumonia (likelihood ratio 0.47, 95% CI 0.32 to 0.67).[5]
Increased work of breathing was found to have a likelihood ratio of 2.1 (95% CI 1.6 to 2.7) for predicting radiographically confirmed pneumonia.[5]
Apnea may be seen, particularly in infants.[1]

Be aware that grunting and cyanosis are signs of severe disease.

Grunting is a sign of impending respiratory failure.[1]
Cyanosis is a sign of severe hypoxemia, although it can be difficult to detect.[1]

Fever and tachypnea are common but nonspecific signs of CAP.[1][9] In a systematic review of 23 studies involving 13,833 children with suspected pneumonia:[5]

Fever >99.5°F (>37.5°C) had a likelihood ratio range of 1.7 to 1.8 for predicting radiographically confirmed CAP (sensitivity 80% to 92%, specificity 47% to 54%).
Tachypnea (respiratory rate [RR] >40 breaths/minute) had a likelihood ratio of 1.5 (95% CI 1.3 to 1.7), sensitivity of 79%, and specificity of 51%.
- Tachypnea is a nonspecific sign but correlates well with hypoxemia.[1][9][20] One study found that in infants <1 year old, an RR ≥70 breaths/minute had a sensitivity of 63% and specificity of 89% for hypoxemia.[27]
- Be aware, however, that some children with CAP have a normal RR.[9]
- Note that tachypnea is defined according to age-related criteria, although suggested reference ranges for different pediatric age groups vary between different sources. Among children ages ≤5 years, the World Health Organization defines tachypnea as RR (breaths/minute) of: >60 at age 0-2 months; >50 at age 2-12 months; >40 at age 1-5 years.[28] A reasonable cut-off for children ages >5 years is an RR >20 breaths/minute.[1][29][30]

Signs of CAP on auscultation may include:[1]

Abnormal or decreased breath sounds such as crackles, rales, crepitation, wheeze, and rhonchi. One study found that crackles and bronchial breathing had a sensitivity of 75% and specificity of 57% for pneumonia.[27]
An absence of breath sounds, with a dull percussion note, is suggestive of CAP complicated by pleural effusion.[9]
Fremitus is increased in uncomplicated CAP (but reduced if pleural effusion has developed).[2]

Note, however, that a systematic review of 23 studies involving a total of 13,833 children with suspected pneumonia found that no auscultatory finding was significantly associated with a radiographic diagnosis of CAP, perhaps because of the relative subjectivity of auscultatory signs and difficulty interpreting them in children.[5]

Early inspiratory crackles

Auscultation sounds: Early inspiratory crackles

Late inspiratory crackles (rales)

Auscultation sounds: late inspiratory crackles (rales)

Check the pulse rate for any signs of tachycardia.[3][9]

Tachycardia is defined according to age-related norms. It is usually considered to be 2 standard deviations above the age-standardized normal heart rate or <10th percentile for age if the child is <1 year old.

Check capillary refill time (CRT).

A CRT >2 seconds is considered to be a sign of severe CAP.[9]

Assessment of severity and appropriate setting for care

Assess the severity of CAP based on symptoms, signs, and risk factors for severe disease. Also look for any evidence of complications.[9] The assessment of severity will influence decisions on appropriate tests, initial antimicrobial therapy, and route of administration.[9]

Look for any signs of sepsis.[2][9] See Sepsis in children.

Refer to the hospital for assessment and management if a child has severe pneumonia or pneumonia with suspected complications.[1]

Nonsevere pneumonia in previously healthy children can be safely managed in the community.[9]
Also take underlying risk factors into account when deciding the appropriate setting for care (e.g., chronic underlying conditions such as congenital heart disease, chronic lung disease of prematurity, cystic fibrosis, bronchiectasis, or immunodeficiency).[9][19]

Be aware that young age is a risk factor for severity of CAP and the need for hospital admission.[1]

Infants and younger children tend to have more severe pneumonia with a greater need for hospitalization and a higher risk of respiratory failure.

Criteria for severe CAP and hospital admission

Arrange hospital admission for any child or infant who has moderate to severe CAP, as indicated by:[1]

Sustained peripheral oxygen saturation <90% on room air. This has been shown to be predictive of failure of outpatient oral antibiotic treatment.
Any one or more of the following signs of respiratory distress:
- Tachypnea: respiratory rate of >60 breaths/minute at age 0-2 months; >50 at age 2-12 months; >40 at age 1-5 years; >20 at age >5 years.
- Dyspnea.
- Suprasternal, intercostal, or subcostal retractions, indicating increased work of breathing.
- Grunting - a sign of impending respiratory failure.
- Nasal flaring or head bobbing.
- Apnea.
- Cyanosis.
- Altered mental status.

Consider hospital admission if:[1]

The child is <6 months old
The child is dehydrated, vomiting, or unable to take oral medication for any other reason
A particularly virulent pathogen such as methicillin-resistant Staphylococcus aureus (MRSA) is suspected or confirmed
There are psychosocial concerns around nonadherence to therapy or difficulty ensuring reliable follow-up.

Symptoms and signs of complicated CAP

Look for any symptoms and signs that might suggest complications of CAP (e.g., parapneumonic effusion, empyema, necrotizing pneumonia, lung abscess). Refer to the hospital for assessment and management if these are present.[1][3][9] Any child with complicated pneumonia should be treated in a center with specific expertise in this area.[2]

Factors reported to be associated with complicated CAP in previously healthy children include: age <2 years; long prehospital duration of fever; asymmetric chest pain at presentation; iron-deficiency anemia; and pretreatment with ibuprofen and acetaminophen.[2] However, some of these factors may be confounded by reverse causation.

Suspect effusion if auscultation reveals absent or severely decreased breath sounds with a dull percussion note.[2][3][9]

Fremitus is reduced in pleural effusion.[2]

Features that raise suspicion of empyema include:[3][9]

Fever >7 days
Pleuritic chest pain
Severe CAP symptoms
No clinical response to antibiotics after 48 hours
Presence of risk factors (e.g., age >3 years, recent varicella infection).

Children with necrotizing pneumonia usually look ill and have a high fever, cough, and tachypnea that last for several days.[2][3]

Hypoxia is common.[2]
The child may experience night sweats and produce foul-smelling sputum.[3]
Mild anemia and hypoalbuminemia are characteristic.[2]
Pleuritic chest pain may be present.[3] Pleural effusion is often detectable on physical exam.[2]
Staphylococcus aureus, frequently methicillin-resistant strains that produce Panton-Valentine leukocidin (PVL) toxin, is associated with necrotizing pneumonia.[2][9] A previous viral respiratory infection can increase the risk for developing necrotizing pneumonia.

Children with lung abscesses usually present with prolonged low-grade fever and cough.[2]

Chest pain, dyspnea, sputum production, and hemoptysis are less common.
Chest exam might be normal or may reveal signs of consolidation.

Initial diagnostic tests

Make a clinical diagnosis of CAP without the need for any blood tests, imaging, or microbiologic tests if the symptoms and signs indicate nonsevere disease in an immunocompetent child.[1][9][18]

Patients managed in the community

Do not order chest x-rays to confirm suspected CAP in a child who is assessed as well enough to be treated as an outpatient (based on evaluation in the community or in a hospital emergency department). Both US and UK guidelines recommend against chest radiography for children managed as outpatients.[1][9]

Chest radiographs cannot reliably distinguish viral from bacterial CAP and do not have a significant impact on clinical outcomes. They are not needed for outpatients in whom the diagnosis of pneumonia is strongly suspected based on the history and clinical exam.[18]
One Cochrane review found that chest x-rays for children with suspected lower respiratory tract infection led to increased use of antibiotics but without any impact on clinical outcome.[31]

Blood cultures and other microbiologic tests are not needed for a fully immunized child with nonsevere CAP.[1][9]

A large majority of blood cultures obtained from such children are sterile.

Rapid diagnostic tests for influenza virus and other respiratory viruses may be useful, if available, in the evaluation of children with CAP in outpatient settings.[1]

A positive influenza test may avert the need for additional tests and antibiotics, while guiding appropriate use of antiviral agents.

Routine complete blood count (CBC) is not needed in children with suspected CAP who are managed in the community.[1]

White blood cell (WBC) count is typically elevated, but the degree of elevation does not reliably distinguish bacterial from viral infection.

Patients managed in the hospital: chest radiography

Avoid routine chest radiography in children referred to the hospital with CAP.[3][9]

There is poor correlation between x-ray appearance and clinical signs and outcome.
The main role of imaging in CAP is to detect complications such as pleural effusion, lung abscess, and bronchopleural fistula.[18]

Reserve chest radiography for any patient who is hospitalized for severe or complicated CAP.[1][3][9] It may also be indicated if the child fails to respond to initial outpatient treatment.[18]

Radiographic confirmation of pneumonia is traditionally defined as the presence of a consolidation, opacity, or infiltrate.[5]
Document the presence, size, and character of parenchymal infiltrates and identify any complications that may require additional interventions over and above antimicrobial therapy and supportive care.[1]

[Figure caption and citation for the preceding image starts]: Chest radiographs confirming pneumonia. Image A: a 6-year-old girl with widespread interstitial changes in both lungs caused by S pneumoniae. Image B: a 1-year-old boy with alveolar changes in the right lower lobe caused by S pneumoniae. Image C: a 2-year-old girl with alveolar changes in the left lower lobe associated with rhinovirus. Image D: a 4-month-old girl with alveolar changes in the right upper lobe associated with parainfluenza 2 and human herpes virusVirkki R, et al. Thorax 2002; 57: 438-41; used with permission [Citation ends]. com.bmj.content.model.Caption@72242900

Signs of complications might be revealed by chest x-ray.[2]

Signs of parapneumonic effusion include blunting of the costophrenic angle and a rim of fluid ascending the lateral chest wall (meniscus sign). Large effusions can appear as a complete white-out.
Lung abscess may show as a well defined thick-walled cavity, often containing an air-fluid level. However, in some cases it may be difficult to distinguish an abscess from consolidation.
Note that the initial phase of necrotizing pneumonia is difficult to detect on chest x-ray because fluid-filled cavitary lesions have the same density as adjacent consolidated lung. Chest computed tomography (CT) may be needed.

[Figure caption and citation for the preceding image starts]: Chest x-ray of complicated pneumonia, showing opacification of the left lung field consistent with a large pleural effusion and empyema. There is associated right-sided bronchial wall thickening and consolidationHaq IJ, et al. BMJ 2017 Mar 2; 356: j686. doi: 10.1136/bmj.j686; used with permission [Citation ends]. com.bmj.content.model.Caption@433b1c83

Patients managed in the hospital: chest ultrasound

If there is suspicion on chest x-ray of a parapneumonic effusion, chest ultrasound is recommended for confirmation.[18] Chest ultrasound may also be appropriate for a child who does not respond to initial outpatient treatment.[18]

Ultrasound is more sensitive than chest radiography to evaluate the pleural space.[2]
It can be used to detect small pleural effusions, estimate the size of the effusion, and show any fibrinous septations and can differentiate pleural effusions from consolidated lung.[2]
It can also differentiate empyema from peripheral lung abscess.[2]
Doppler ultrasound can detect necrotic changes before they become apparent on CT.[2]

A wider potential role for bedside lung ultrasound in diagnosis of uncomplicated CAP is under ongoing investigation.[10]

A meta-analysis of five studies found a sensitivity of 96% and specificity of 93% for diagnosing radiographically confirmed CAP when ultrasound was undertaken by skilled sonographers.[32]
The accuracy of point-of-care ultrasound in the hands of less skilled clinicians remains unclear.[33]
Further research is needed to determine whether bedside ultrasonography has potential utility for diagnosis of uncomplicated CAP in the emergency department.[10]

Patients managed in the hospital: computed tomography (CT)

CT chest with intravenous contrast may be useful in limited circumstances in a small subgroup of children with complicated pneumonia, particularly if necrotizing pneumonia is suspected.[2][18]

In most children with complicated CAP, chest CT does not provide any useful clinical information to guide management or indicate prognosis over and above that gained from ultrasound.[2]
Reserve chest CT with intravenous contrast for diagnostic doubt (e.g., suspicion of malignancy) or for when appropriate treatment does not lead to clinical improvement.[2]
On chest CT, necrotizing pneumonia will show as a rapid transition from a thin-walled fluid-filled compartment to cavitation. Lung abscess will show as a thick-walled compartment with the fluid, with or without air.[2]

Microbiology tests

Microbiologic tests are not needed for nonsevere disease.[9] Only seek a microbiologic diagnosis in children:[1][2][9][17]

With severe disease who are admitted to the hospital
Who have potential complications
Who have suspicion for an unusual pathogen that might require a non-standard antimicrobial regimen
Who fail to respond to initial therapy.

Defining causative pathogens can be challenging.[2][3]

Clinical and radiologic features do not reliably distinguish bacterial from viral etiology. Moreover, coinfection is common.[7][9]
Blood cultures are rarely performed in patients who are managed in the community and demonstrate a poor yield in hospital patients.
Obtaining lower respiratory tract cultures from young children is difficult.
Invasive investigations such as pleural aspiration are reserved for severe cases.
Use of sputum, nasopharyngeal, and oropharyngeal samples is limited by the difficulty in distinguishing colonizing organisms from pathogenic ones. However, these samples can be useful to detect organisms that are almost invariably pathogenic, such as RSV and influenza virus.[2]

Where microbiologic tests are indicated because of severe or complicated disease, consider:

Blood cultures. Only order blood cultures for children who are hospitalized for severe CAP or complicated CAP (ideally before antibiotics are given, if feasible).[1][2][9] Cultures are often negative and in some cases this is because of antibiotic therapy initiated prior to cultures being obtained.[1] Samples are rarely positive; hence, the impact on clinical management is usually small. Nonetheless, culture-directed antimicrobial therapy may be associated with improved clinical outcome in those who do have a pathogen identified.[9]
- Studies have reported that only around 2.5% to 7% of blood cultures are positive in children hospitalized for CAP.[34][35] This may sometimes be because of prior antibiotic therapy in the community.[2]
- Pneumococcal pneumonia is seldom a bacteremic illness, and S pneumoniae is cultured in the blood in <5% of cases.[9] Where this is the case, children who show clear clinical improvement do not need repeat blood cultures to confirm resolution of pneumococcal bacteremia.[1]
- If blood cultures show bacteremia caused by Staphylococcus aureus, repeat cultures are required to document resolution, regardless of clinical status.[1]
Nasopharyngeal swabs for polymerase chain reaction (PCR) multiplex testing.
- Rapid diagnostic tests using PCR-based assays can be performed on samples from the nasopharynx, throat, or pleural fluid.[9] This can be particularly useful to avoid inappropriate antibiotic therapy if a viral or atypical bacterial etiology is suspected.[1] Nasopharyngeal secretions are relatively easy to obtain, and the use of PCR testing has been reported to result in pathogen identification in 65% to 83% of cases.[3]
- Use of rapid multiplex point-of-care PCR tests for individuals who present with respiratory tract infection has become routine in many hospitals since the COVID-19 pandemic. These enable nasal or nasopharyngeal specimens to be tested simultaneously for multiple pathogens, with results available within 1-2 hours.[36][37] However, one randomized trial involving 1243 children presenting to an emergency department with fever and/or respiratory symptoms or signs failed to show any significant impact on the proportion of children who were prescribed antibiotics.[38]
- Note that nasopharyngeal culture is uninformative because of the difficulty in distinguishing pathogenic bacteria from normal flora.[9]
- If an atypical pathogen is suspected, bear in mind the mixed evidence on the value of PCR testing. A study from the Netherlands suggested that nasal PCR testing for M pneumoniae has similar rates of positivity in symptomatic children versus asymptomatic carriers, although a subsequent US study failed to support this observation.[4][39] See Atypical pneumonia.
- Be aware that identification of a viral etiology (e.g., influenza) does not exclude a bacterial pathogen because of the high incidence of coinfection.

Consider obtaining a sputum sample for culture and Gram stain if an older child or adolescent has been hospitalized with severe CAP.[1]

Many younger children cannot produce an adequate specimen, but older children and adolescents often can.

If pleural fluid is obtained (e.g., because of severe CAP or evidence of pleural effusion), send it for:[1][2][9]

Microscopy and culture (including Gram staining, acid-fast bacilli staining, Mycobacterium tuberculosis testing, antibiotic sensitivity testing).
Pneumococcal antigen detection and/or PCR. PCR on pleural fluid is more specific and more sensitive than PCR on blood samples, and pleural fluid testing for pneumococcal antigen has a high positive predictive value for pneumococcal empyema.[2]

If the child has a lymphocytic effusion or risk factors for tuberculosis (TB), or lives in an area with high incidence of TB, test for M tuberculosis, using induced sputum if feasible or PCR testing of a nasopharyngeal sample.[2]

If a child requires mechanical ventilation for severe or life-threatening CAP, obtain tracheal aspirates at the time of endotracheal tube placement. Send them for Gram stain and culture and for guided testing for viral pathogens.[1]

For children with influenza virus as the suspected etiology for CAP, rapid PCR testing of endotracheal tube secretions may yield positive results despite negative nasopharyngeal test results.

Reserve bronchoscopy with bronchoalveolar lavage (BAL) for immunocompetent children with severe CAP whose initial diagnostic tests fail to yield any positive results.[1]

BAL is complex in children, particularly neonates, because of small airways.
Flexible bronchoscopy is well tolerated. However, this test is only available in some centers and has a small pathogenic yield in children who are not immunosuppressed.[2]

Do not use urinary antigen detection tests for diagnosis of pneumococcal pneumonia.[1][9]

False positive results are common.

Laboratory tests

Order a CBC, serum electrolytes, blood urea nitrogen (BUN), and liver function tests for any patient with severe pneumonia. Interpret the results in the context of the clinical exam and other laboratory and imaging studies.[1][9]

WBC count is typically elevated, but the degree of elevation does not reliably distinguish bacterial from viral infection.
The presence of anemia or thrombocytopenia may raise concern for hemolytic-uremic syndrome, a rare complication of pneumococcal pneumonia.
Measurement of serum electrolytes may be helpful in assessing hydration status in children with reduced fluid intake. Hyponatremia is common in children with CAP.[2]

Acute phase reactants (WBC count, procalcitonin, C-reactive protein [CRP], erythrocyte sedimentation rate [ESR]) are unreliable for distinguishing bacterial from viral etiology. However, they can be useful in severe CAP when measured serially to monitor response to treatment.[2] Results must be interpreted in the context of the clinical exam and other laboratory and imaging studies.[1]

Recommendations on measuring acute phase reactants vary, so check your local protocol.
In the US, the PIDS/IDSA 2011 guideline:[1]
- Recommends against using ESR, CRP, and serum procalcitonin as the sole means to distinguish viral from bacterial causes of CAP.
- States that measurement of ESR, CRP, and procalcitonin is not necessary for fully immunized children with suspected CAP managed in the community but may provide useful information for those with more severe disease.
- States that elevated procalcitonin can be a marker of serious bacterial infection, although values vary widely. If procalcitonin is low, this can be a pointer toward viral pneumonia. If a child with a confirmed viral pneumonia has elevated procalcitonin, this can raise suspicion of bacterial coinfection.
- Recommends to consider using serial results in conjunction with clinical findings to assess response to therapy, because declining levels of CRP or procalcitonin may correlate with improved clinical symptoms.
Subsequent findings have suggested that a low procalcitonin level has a high negative predictive value for bacterial CAP.[40][41] Procalcitonin levels <0.25 nanograms/mL can accurately identify children at lower risk of bacterial CAP, for whom antibiotics are unlikely to be helpful.[7][40][42]

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