Community-acquired pneumonia in children

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

Key Points

Paediatric community-acquired pneumonia (CAP) is an acute lower respiratory tract infection in a previously healthy child caused by an infection acquired outside of hospital.[1][9] There is no reliable way clinically to distinguish between bacterial and viral aetiology.[9] Most cases are caused by viruses, with respiratory syncytial virus (RSV) and human rhinovirus the most common aetiologies.[4] Streptococcus pneumoniae is the most common typical bacterial pathogen.[4]
Symptoms are often fairly non-specific but typically include fever, cough, tachypnoea, and dyspnoea. Hypoxaemia is often found on pulse oximetry. Common signs on physical examination 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][18]
In a previously healthy, immunocompetent child with non-severe symptoms, CAP can be diagnosed clinically without the need for any blood tests, imaging, or microbiology investigations.[1][9][19]
If a child has severe symptoms or suspected complications (e.g., pleural effusion, empyema, necrotising 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 hospitalised 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 non-specific.[3][9] A careful history and thorough physical examination 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, immunisation status, and recent travel history (as this may have a bearing on potential aetiology 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: tachypnoea; chest crackles; nasal flaring; chest indrawing; cyanosis; oxygen saturation ≤95% on room air.[9][20]

One multi-centre 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 hypoxaemia.[21] 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 multi-centre study of 2358 cases of radiographically confirmed CAP.[4]
Dyspnoea or difficulty breathing. Some 70% of 2358 children with radiographic evidence of pneumonia had dyspnoea.[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][22][23] However, wheeze combined with other typical symptoms can be a pointer towards possible CAP. A study of 526 children evaluated for wheezing in the emergency department found that only 4.9% had radiographically confirmed pneumonia.[24] However, when wheeze was accompanied by fever 6.9% were found to have radiographic evidence of pneumonia, and when wheeze, fever, and hypoxaemia (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 hypoxaemia.[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, hypoxaemia 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][25]
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 anatomical 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]

Aetiology

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

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

Consider bacterial CAP if the child has a persistent or repetitive fever >38.5°C (>101.3°F) 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 tachypnoea. 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.[18]

M pneumoniae infection tends to have peaks or outbreaks every 3-7 years.[26] 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][19] However, a Cochrane review of seven studies covering 1491 children in hospital settings found that it is not possible to reliably diagnose pneumonia caused by M pneumoniae based on clinical symptoms and signs.[27]
For more detail, see Atypical pneumonia.

Physical examination

Conduct a thorough physical examination 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 hypoxaemia (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]
Apnoea 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 hypoxaemia, although it can be difficult to detect.[1]

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

Fever >37.5°C (>99.5°F) had a likelihood ratio range of 1.7 to 1.8 for predicting radiographically confirmed CAP (sensitivity 80% to 92%, specificity 47% to 54%).
Tachypnoea (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%.
- Tachypnoea is a non-specific sign but correlates well with hypoxaemia.[1][9][21] One study found that in infants <1 year old, an RR ≥70 breaths/minute had a sensitivity of 63% and specificity of 89% for hypoxaemia.[28]
- Be aware, however, that some children with CAP have a normal RR.[9]
- Note that tachypnoea is defined according to age-related criteria, although suggested reference ranges for different paediatric age groups vary between different sources. Among children aged ≤5 years, the World Health Organization defines tachypnoea as RR (breaths/minute) of: >60 at age 0-2 months; >50 at age 2-12 months; >40 at age 1-5 years.[29] The UK National Institute for Health and Care Excellence (NICE) defines it as RR (breaths/minute) of: >60 at age 0-5 months; >50 at age 6-12 months; >40 at age 1-5 years.[20] Recommended cut-offs for children aged >5 years vary, so check your local protocol. In the US, the CAP guideline published by the Pediatric Infectious Disease Society/Infectious Diseases Society of America (PIDS/IDSA) suggests a threshold to indicate respiratory distress of an RR >20 breaths/minute for children aged >5 years.[1] The NHS England national paediatric early warning system (PEWS) uses a threshold for 5- to 12-year-olds of >25 breaths/minute for mild respiratory distress, >40 for moderate respiratory distress, and >50 for severe respiratory distress.[30] For children ≥13 years old, PEWS defines RR >25 breaths/minute as mild respiratory distress, >30 as moderate respiratory distress, and >40 as severe respiratory distress.[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.[28]
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-standardised normal heart rate or <10th percentile for age if the child is <1 year old.
The UK National Institute for Health and Care Excellence (NICE) defines tachycardia as follows for children <5 years old:[20]
- >160 beats per minute (bpm) for infants <1 year old.
- >150 bpm for children aged 12-24 months.
- >140 bpm for children aged 2-5 years.

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 investigations, initial antimicrobial therapy, and route of administration.[9]

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

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

Non-severe 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][20]

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 hospitalisation and a higher risk of respiratory failure.

Criteria for severe CAP and hospital admission

Precise criteria for severe pneumonia vary, so check your local protocols and guidelines. The table below summarises the criteria for severe CAP from major US and UK guidelines.

	UK National Institute for Health and Care Excellence (NICE), 2021[18][20]	British Thoracic Society (BTS), 2011[9]	Pediatric Infectious Disease Society/Infectious Diseases Society of America (PIDS/IDSA), 2011[1]
Criteria for severe CAP	Features of severe CAP in children include:[18] Difficulty breathing. Oxygen saturation <90%. Raised heart rate. Grunting. Very severe chest indrawing. Inability to drink or breastfeed. Lethargy or reduced level of consciousness. NICE also recommends that:[20] A temperature ≥38.0°C (≥100.4°F) in an infant <3 months old is a red flag for high risk of serious illness, and a temperature ≥39.0°C (≥102.2°F) in a child aged 3-6 months is an amber flag for intermediate risk of serious illness. A CRT ≥3 seconds in a child <5 years old is an amber flag for intermediate risk of serious illness.	Severe pneumonia is defined by the presence of one or more of the following features:[9] Oxygen saturation <92%. Temperature >38.5°C (>101.3°F). Significant tachypnoea: respiratory rate >70 breaths/minute in infants or >50 breaths/minute in older children. Moderate to severe chest recession (more common in infants) or severe difficulty in breathing (more common in older children). Nasal flaring, grunting, or intermittent apnoea. Cyanosis. Significant tachycardia according to age-related parameters. Capillary refill time (CRT) ≥2 seconds. Not feeding (infant) or signs of dehydration. The BTS guideline also recommends hospital care for any child in whom auscultation reveals absent breath sounds with a dull percussion note, because this raises the possibility of CAP complicated by effusion.[9]	Arrange hospital admission for any child or infant who has moderate to severe CAP, as indicated by one of both of:[1] Sustained peripheral oxygen saturation <90% on room air. Any one or more of the following signs of respiratory distress: Tachypnoea: 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; Dyspnoea; Suprasternal, intercostal, or subcostal retractions, indicating increased work of breathing; Grunting - a sign of impending respiratory failure; Nasal flaring or head bobbing; Apnoea; 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 MRSA is suspected or confirmed. There are psychosocial concerns around non-adherence to therapy or difficulty ensuring reliable follow-up.

UK National Institute for Health and Care Excellence (NICE), 2021[18][20]

British Thoracic Society (BTS), 2011[9]

Pediatric Infectious Disease Society/Infectious Diseases Society of America (PIDS/IDSA), 2011[1]

Criteria for severe CAP

Features of severe CAP in children include:[18]

Difficulty breathing.
Oxygen saturation <90%.
Raised heart rate.
Grunting.
Very severe chest indrawing.
Inability to drink or breastfeed.
Lethargy or reduced level of consciousness.

NICE also recommends that:[20]

A temperature ≥38.0°C (≥100.4°F) in an infant <3 months old is a red flag for high risk of serious illness, and a temperature ≥39.0°C (≥102.2°F) in a child aged 3-6 months is an amber flag for intermediate risk of serious illness.
A CRT ≥3 seconds in a child <5 years old is an amber flag for intermediate risk of serious illness.

Severe pneumonia is defined by the presence of one or more of the following features:[9]

Oxygen saturation <92%.
Temperature >38.5°C (>101.3°F).
Significant tachypnoea: respiratory rate >70 breaths/minute in infants or >50 breaths/minute in older children.
Moderate to severe chest recession (more common in infants) or severe difficulty in breathing (more common in older children).
Nasal flaring, grunting, or intermittent apnoea.
Cyanosis.
Significant tachycardia according to age-related parameters.
Capillary refill time (CRT) ≥2 seconds.
Not feeding (infant) or signs of dehydration.

The BTS guideline also recommends hospital care for any child in whom auscultation reveals absent breath sounds with a dull percussion note, because this raises the possibility of CAP complicated by effusion.[9]

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

Sustained peripheral oxygen saturation <90% on room air.
Any one or more of the following signs of respiratory distress: Tachypnoea: 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; Dyspnoea; Suprasternal, intercostal, or subcostal retractions, indicating increased work of breathing; Grunting - a sign of impending respiratory failure; Nasal flaring or head bobbing; Apnoea; 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 MRSA is suspected or confirmed.
There are psychosocial concerns around non-adherence 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, necrotising pneumonia, lung abscess). Refer to hospital for assessment and management if these are present.[1][3][9] Any child with complicated pneumonia should be treated in a centre with specific expertise in this area.[2]

Factors reported to be associated with complicated CAP in previously healthy children include: age <2 years; long pre-hospital duration of fever; asymmetrical chest pain at presentation; iron-deficiency anaemia; and pre-treatment with ibuprofen and paracetamol.[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 necrotising pneumonia usually look ill and have a high fever, cough, and tachypnoea that last for several days.[2][3]

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

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

Chest pain, dyspnoea, sputum production, and haemoptysis are less common.
Chest examination might be normal or may reveal signs of consolidation.

Initial diagnostic investigations

Make a clinical diagnosis of CAP without the need for any blood tests, imaging, or microbiological investigations if the symptoms and signs indicate non-severe disease in an immunocompetent child.[1][9][19]

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 examination.[19]
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 microbiological investigations are not needed for a fully immunised child with non-severe 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 investigations and antibiotics, while guiding appropriate use of antiviral agents.

Routine full blood count (FBC) 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 hospital: chest radiography

Avoid routine chest radiography in children referred to 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.[19]

Reserve chest radiography for any patient who is hospitalised for severe or complicated CAP.[1][3][9] It may also be indicated if the child fails to respond to initial outpatient treatment.[19]

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@3c780b80

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 necrotising 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@4d34d1bc

Patients managed in hospital: chest ultrasound

If there is suspicion on chest x-ray of a parapneumonic effusion, chest ultrasound is recommended for confirmation.[19] Chest ultrasound may also be appropriate for a child who does not respond to initial outpatient treatment.[19]

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 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 necrotising pneumonia is suspected.[2][19]

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, necrotising 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 investigations

Microbiological investigations are not needed for non-severe disease.[9] Only seek a microbiological diagnosis in children:[1][2][9][18]

With severe disease who are admitted to 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.

Consider seeking a microbiological diagnosis if a child who is treated in hospital has a comorbidity.[18]

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

Clinical and radiological features do not reliably distinguish bacterial from viral aetiology. Moreover, co-infection 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 colonising 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 microbiological investigations are indicated because of severe or complicated disease, consider:

Blood cultures. Only order blood cultures for children who are hospitalised 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 hospitalised for CAP.[34][35] This may sometimes be because of prior antibiotic therapy in the community.[2]
- Pneumococcal pneumonia is seldom a bacteraemic 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 bacteraemia.[1]
- If blood cultures show bacteraemia 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 aetiology 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 randomised 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 aetiology (e.g., influenza) does not exclude a bacterial pathogen because of the high incidence of co-infection.

Consider obtaining a sputum sample for culture and Gram stain if an older child or adolescent has been hospitalised 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 aetiology 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 investigations 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 investigation is only available in some centres 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 investigations

Order a FBC, serum electrolytes, urea, and liver function tests for any patient with severe pneumonia. Interpret the results in the context of the clinical examination 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 anaemia or thrombocytopenia may raise concern for haemolytic-uraemic syndrome, a rare complication of pneumococcal pneumonia.
Measurement of serum electrolytes may be helpful in assessing hydration status in children with reduced fluid intake. Hyponatraemia 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 aetiology. 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 examination 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 immunised 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 towards viral pneumonia. If a child with a confirmed viral pneumonia has elevated procalcitonin, this can raise suspicion of bacterial co-infection.
- 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.
The British Thoracic Society 2011 guideline recommends against routine testing of acute phase reactants for a child referred to hospital with suspected CAP, on the basis that they are of no utility in distinguishing viral from bacterial infection or guiding management.[9]
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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