How to diagnose bronchiolitis, especially in pediatric patients?

How to Diagnose Bronchiolitis in Pediatric Patients

Diagnose bronchiolitis based on history and physical examination alone—do not routinely order chest radiographs, viral testing, or laboratory studies. 1

Clinical Diagnosis Framework

Essential Clinical Features

Bronchiolitis presents as a constellation of specific signs and symptoms in children younger than 2 years of age 1:

• Viral upper respiratory prodrome (rhinorrhea) followed by lower respiratory tract involvement 1
• Lower respiratory signs: wheezing, rales, tachypnea 1
• Increased respiratory effort: grunting, nasal flaring, intercostal and/or subcostal retractions 1
• Cough as a prominent feature 1

The diagnosis is clinical—most clinicians recognize this pattern, particularly during winter season when viral bronchiolitis is most common 1.

Critical History Elements to Assess

When taking the history, focus on these specific factors 1:

• Effects on mental status, feeding, and hydration (these indicate severity)
• Age (infants <12 weeks are high-risk) 1
• History of prematurity 1
• Underlying cardiopulmonary disease (hemodynamically significant congenital heart disease, chronic lung disease/bronchopulmonary dysplasia) 1
• Immunodeficiency 1
• Previous wheezing episodes 1
• In utero smoke exposure 1
• History of apnea (particularly relevant in young or premature infants) 1

Physical Examination Specifics

Respiratory rate assessment 1:

• Count over a full 60 seconds (more accurate than shorter observations) 1
• Normal rates decrease with age: 50th percentile is 41 breaths/minute at 0-3 months, declining to 31 breaths/minute at 12-18 months 1
• Tachypnea ≥70 breaths/minute has been associated with increased risk of severe disease 1, 2

Work of breathing indicators 1, 2:

• Nasal flaring
• Grunting
• Intercostal retractions
• Subcostal retractions

Important examination nuance: Upper airway obstruction contributes to work of breathing—suctioning and positioning may decrease work of breathing and improve examination quality 1. Serial observations over time provide more valid assessment than a single examination, given the variable and dynamic nature of bronchiolitis 1.

What NOT to Do: Avoiding Unnecessary Testing

Chest Radiography

Do not obtain routine chest radiographs 1. The evidence is clear:

• Chest radiograph abnormalities do not correlate well with disease severity 1
• Approximately 25% of hospitalized infants have radiographic atelectasis or infiltrates that are often misinterpreted as bacterial infection 3
• Prospective studies show children who receive radiographs are more likely to receive unnecessary antibiotics without any difference in time to recovery 1

Exception: Radiography may be useful when the hospitalized child does not improve at the expected rate, if severity requires further evaluation, or if another diagnosis is suspected 1.

Laboratory Studies

Do not routinely order laboratory tests 1:

• Complete blood counts have not been shown useful in diagnosing bronchiolitis or guiding therapy 1
• The occurrence of serious bacterial infections (UTIs, sepsis, meningitis) is very low (<1%) 1, 2, 3

Viral Testing

Do not routinely perform virologic testing for RSV 1:

• While RSV tests demonstrate high predictive value during peak season, the knowledge gained rarely alters management decisions or outcomes 1
• Exception: Virologic testing may be useful when cohorting of patients is feasible (infection control purposes) 1

Risk Stratification for Severe Disease

Assess these high-risk factors that require closer monitoring and may alter management decisions 1, 2:

• Age <12 weeks (particularly <1 month)
• Prematurity (especially <32 weeks gestation or <48 weeks postconceptional age)
• Hemodynamically significant congenital heart disease (receiving medication for CHF, moderate-to-severe pulmonary hypertension, or cyanotic heart disease)
• Chronic lung disease/bronchopulmonary dysplasia
• Immunodeficiency

One large study found no apnea events in low-risk infants: age >1 month for full-term infants or 48 weeks postconceptional age for preterm infants, with no previous apneic events 1.

Pulse Oximetry Considerations

Use pulse oximetry judiciously 1, 2:

• Pulse oximetry can reliably detect hypoxemia not suspected on physical examination 1
• Among outpatients, evidence differs on whether mild reductions in SpO2 (<95% on room air) predict disease progression 1
• Critical pitfall: Continuous pulse oximetry may lead to less careful clinical monitoring—serial clinical assessments are more important than continuous monitoring in stable infants 2
• Do not treat based solely on pulse oximetry readings without clinical correlation, as transient desaturations can occur in healthy infants 2

Differential Diagnosis Considerations

The primary goal is differentiating infants with probable viral bronchiolitis from those with other disorders 1:

• Normal respiratory rate suggests low risk of significant viral or bacterial lower respiratory tract infection (negative likelihood ratio ~0.5) 1
• However, tachypnea does not distinguish between viral and bacterial disease 1

Evidence Quality Summary

The American Academy of Pediatrics guidelines provide Level B evidence (diagnostic studies with minor limitations and observational studies with consistent findings) supporting clinical diagnosis without routine testing 1. The benefits-harms assessment shows a preponderance of benefit over harm for this approach, with cost savings and limitation of radiation/blood tests outweighing the minimal risk of misdiagnosis 1.