Tests
1st tests to order
pulse oximetry
Test
A noninvasive method to measure oxyhemoglobin saturation and detect hypoxemia. It provides an assessment of acute disease severity, but data on its ability to predict clinical outcomes are inconsistent.[43][63]
Pulse oximetry is not recommended for outpatients with mild disease.[49]
In general, infants with viral bronchiolitis are more hypoxemic than their chest x-ray findings would suggest.
Guideline statements differ in their recommended lowest acceptable oxyhemoglobin saturation limits. The American Academy of Pediatrics recommends that infants who are hypoxemic be given supplemental oxygen to maintain an oxyhemoglobin saturation (saturation of peripheral oxygen, SpO₂) of at least 90%, the point at which small decreases in arterial partial pressure of oxygen (PaO₂) are associated with large changes in SpO₂.[43][53]
In one study on infants with bronchiolitis, an oxygen saturation target of 90% or higher was found to be as safe and clinically effective as one of 94% or higher.[54]
No long-term neurodevelopmental studies have been performed to determine the safety of lower oxyhemoglobin saturation targets, leading some guidelines to recommend oxygen supplementation if the oxyhemoglobin saturation falls below 92%.[55]
Although there is not complete consensus among different guidelines, most recommend the use of intermittent rather than continuous pulse oximetry monitoring, unless the child is receiving supplemental oxygen.[50][51]
In nonhypoxemic inpatients, intermittent pulse oximetry did not affect rate of escalation of care or duration of oxygen therapy, compared with continuous pulse oximetry monitoring.[52]
Result
hypoxemia
Investigations to avoid
broad respiratory pathogen panels
Recommendations
Avoid ordering broad respiratory pathogen panels, including comprehensive viral panel testing, unless the result will directly influence management decisions.[58][59]
Rationale
Bronchiolitis is a clinical diagnosis and usually does not require confirmatory viral testing unless an infant receiving monthly prophylaxis is hospitalized with bronchiolitis.[43] There is also a lack of consistent evidence to demonstrate the impact of comprehensive viral panel results on clinical outcomes.[66]
Tests to consider
enzyme-linked immunosorbent assay (ELISA) rapid antigen detection
Test
Commercial ELISAs are available for respiratory syncytial virus (RSV) and influenza but should be used only when the prevalence of disease is high in the community.
Positive rapid antigen tests are usually predictive of the viral agent of bronchiolitis, but a negative result does not rule out the presence of the virus. Rapid antigen testing, therefore, is not necessary for diagnosis of bronchiolitis. However, identifying the specific agent may be useful for infection control cohorting in the hospital setting, although there is some question as to whether testing adds any advantage over routine use of contact precautions.[47][55] A positive antigen test may also reduce the need for further investigations in a febrile infant and reduce the use of antibiotics.
Testing is recommended for infants receiving immunoprophylaxis with palivizumab or nirsevimab who experience a breakthrough episode of bronchiolitis. If RSV is detected, monthly immunoprophylaxis should be discontinued because of the low likelihood of a second RSV infection in the same year.[43]
Testing can provide epidemiologic data that could affect care beyond that of the individual patient.[50]
Result
positive detection of viral antigen
chest x-ray
Test
Do not obtain radiographs for children presenting with typical signs and symptoms of bronchiolitis as radiographs rarely yield important positive findings and expose children to unnecessary radiation.[43][58]
Although not required for clinical diagnosis, chest radiography may be obtained in the setting of severe bronchiolitis or if infants with clinically diagnosed bronchiolitis are not improving at the expected rate.
Radiographic abnormalities in bronchiolitis can resemble those seen in bacterial pneumonia, and radiographs should not be used as the sole criterion for the diagnosis of bacterial pneumonia.[43][53]
Result
hyperinflation, interstitial inflammation, atelectasis
reverse transcriptase polymerase chain reaction (RT-PCR)
Test
RT-PCR is more sensitive than ELISA.
In addition, positive nucleic acid testing for non-RSV organisms may reflect prolonged viral shedding from an unrelated previous illness.
Result
positive detection of viral nucleic acid
Emerging tests
infant pulmonary function tests
Test
Most infant pulmonary function test (IPFT) techniques require sedation and are very labor intensive, rendering them unsuitable for clinical use.[64]
Respiratory inductive plethysmography is a noninvasive method to assess respiratory function without sedation.[65]
Result
may show airflow obstruction that correlates with clinical disease severity; some infants demonstrate an improvement in airflow after bronchodilator inhalation
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