Bronchiolitis and bronchopneumonia are the commonest forms of lower respiratory tract infection (LRTI) in children under two-years-old, and are often lumped together under the umbrella term LRTI, but experts caution that a proper diagnosis of the two is required, especially when administering antibiotics.
Writing in the SA Medical Journal, they say in the era of improved childhood pneumococcal and Haemophilus influenzae type b conjugate vaccination, both conditions are predominantly caused by viruses, and among hospitalised cases, the commonest cause is respiratory syncytial virus (RSV) (40%-80% of bronchiolitis and 20%-40% of bronchopneumonia).
Other respiratory viral pathogens commonly associated with childhood LRTI include human metapneumovirus, influenza, parainfluenza, adenovirus and human rhinovirus.
Although bronchiolitis is predominantly caused by a single viral pathogen, a substantial proportion of children with LRTI will have multiple potential pathogens detectable by molecular testing of respiratory samples, so determining the causative bacterial and/or viral pathogens in cases of mixed infection remains challenging.
Bacterial co-infection is uncommon in bronchiolitis, but it is reported more frequently in children with severe disease, including those requiring invasive ventilation.
The World Health Organisation (WHO) case definition of pneumonia (with key presenting complaints of ‘difficulty breathing or cough’) is not specific and would include most cases of bronchiolitis.
This definition is intended to be non-specific to reduce the high pneumonia-related mortality in low- and middle-income countries (LMICs) through oxygen and antibiotic use.
However, with the emergence of widespread antimicrobial resistance and increasing recognition of the importance of antimicrobial stewardship, a more targeted approach to the use of antibiotics is required. While empirical antibiotics are indicated for children with bronchopneumonia, antibiotics are not recommended for bronchiolitis.
A proportion of children with bronchiolitis may, however, have bacterial co-infection(s) that warrant antibiotic therapy.
In this latest study and commentary, led by researchers from the University of the Witwatersrand, the team highlights the challenges of identifying children with bacterial co-infection and proposes a pragmatic management strategy for clinicians working in South African healthcare facilities.
Differentiating bronchiolitis from bronchopneumonia
In the absence of a gold-standard laboratory, radiological and/or microbiological test, a careful clinical examination, as well as epidemiological information (for example, the timing of the RSV season), becomes an indispensable requirement to differentiate bronchiolitis from bronchopneumonia.
Children with bronchiolitis have chest hyperinflation and minute-to-minute variation in clinical findings. The Hoover sign, i.e. subcostal recessions when a flattened diaphragm pulls laterally against the lower chest wall, may also be present (but is not pathognomonic of bronchiolitis).
Chest auscultation usually reveals diffuse crackles with or without wheezing. Bronchiolitis may also present as apnoeic episodes in neonates and young infants.
Common reasons for misdiagnosing bronchiolitis as pneumonia include: (i) failure to detect hyperinflation; (ii) equating the detection of crackles with bronchopneumonia; (iii) failure to detect a prolonged expiratory phase and/or wheezing; and (iv) mistaking normal bronchovesicular breath sounds for bronchial breathing.
To minimise these errors, clinicians should familiarise themselves with normal infant breath sounds. It is important to perform auscultation over both axillae and the lower zones posteriorly and laterally, because these auscultatory regions are further from major airways.
There are no absolute clinical features, including the severity of respiratory distress, that indicate bacterial co-infection in a child with bronchiolitis. Although several clinical scoring systems have been developed to assess the severity of bronchiolitis, these need further refinement and validation across multiple settings.
An example of such a scoring system is the modified Tal score, but this has not been validated in SA.
Scoring systems can inform appropriate management and decision-making, but do not minimise the need for careful, regular monitoring, especially during the peak of disease severity (usually days two to four of illness.
These systems are also subject to intra- and inter-observer variability. It is recommended that the same clinical severity criteria or scoring system be used throughout the child’s admission to provide consistency and allow tracking of deterioration or improvement.
Some clinical signs are more subjective (level of retractions/recessions, breath sound intensity, and presence and loudness of wheezing) than others, and their recognition will depend on the experience of the clinician.
When assessing severity, focus on objective parameters first; these include respiratory rate, oxygen saturation, willingness to feed (normal, less than usual or not interested), and general behaviour.
The respiratory rate should be evaluated over a full minute to account for the periodic breathing patterns in young infants. Failure of normalisation of oxygen saturation while receiving appropriate oxygen therapy may indicate respiratory failure.
The context in which the respiratory assessment takes place is also important; note the child’s level of consciousness (calm, asleep, crying or agitated) and whether they are febrile, coughing or feeding during the examination, as these may alter their clinical signs. Where possible, and after parental or caregiver consent has been obtained, video recordings of the breathing patterns should be considered.
Investigations
In general, apart from screening for HIV infection, no additional investigations (e.g. full blood count, serum electrolytes, blood culture) are warranted in a child with typical mild or moderately severe bronchiolitis – this constitutes most children hospitalised with bronchiolitis.
Measurement of biomarkers for bacterial co-infection may be indicated in children with severe bronchiolitis, those with associated comorbidities (preterm <29 weeks’ gestation, chronic lung disease of prematurity, congenital heart disease with increased pulmonary blood flow, immunodeficiency or neuromuscular disorders), those who are not improving as expected after 48 hours of admission, or those presenting with recurrent episodes of bronchiolitis.
Until a better diagnostic test becomes available, a C-reactive protein (CRP) level ≥40 mg/L is a reasonable indication to initiate antibiotic therapy.
A chest radiograph is indicated in children who may have alternative explanations for wheezing (e.g. endobronchial tuberculosis, congenital anatomical compression of the airway, foreign body), or if complications are suspected during an episode of bronchiolitis
Study details
Bronchiolitis v. bronchopneumonia: Navigating antibiotic use within the lower respiratory tract infection spectrum
Z Dangor, S G Lala, C Verwey, G Reubenson, D White, D P Moore, P Jeena, R Masekela, H J Zar.
Published in the South African Medical Journal in June 2023
Bronchiolitis, a common reason for infant hospitalisation in South Africa (SA), is caused by viral pathogens. Bronchiolitis is typically an illness of mild to moderate severity that occurs in well-nourished children. Hospitalised SA infants frequently have severe disease and/or coexisting medical conditions, and these cases of bronchiolitis may have bacterial co-infection that requires antibiotic therapy. However, the existence of widespread antimicrobial resistance in SA warrants the judicious use of antibiotics. This commentary describes: (i) common clinical pitfalls leading to an incorrect diagnosis of bronchopneumonia; and (ii) considerations for antibiotic therapy in hospitalised infants with bronchiolitis. If antibiotics are prescribed, the indication for their use should be clearly stated, and antibiotic therapy must be stopped promptly if investigations indicate that bacterial co-infection is unlikely. Until more robust data emerge, we recommend a pragmatic management strategy to inform antibiotic use in hospitalised SA infants with bronchiolitis in whom bacterial co-infection is suspected
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