Things We Do for No Reason™: Lumbar Punctures in Low-Risk Febrile Infants with Bronchiolitis

While clinical guidelines for bronchiolitis are well established,⁷ the evaluation and management of fever in an infant <90 days old remains a challenge because of concern for missing a bloodstream infection or meningitis. Meningitis can devastate an infant neurologically.⁹ Signs and symptoms of bacterial meningitis in infants are not specific, including the physical exam.¹⁰ Blood cultures are only concomitantly positive in 62% of cases of culture-confirmed bacterial meningitis.¹¹

Several risk stratification algorithms exist to evaluate the likelihood of bacterial infections in febrile infants (Table). Two of the most common criteria—the Boston and Philadelphia—were validated using CSF cell count data. Other algorithms do not require an LP.^12-15 All of the fever criteria algorithms have several limitations including lack of robust validation studies, under-powered methodologies (particularly for meningitis), and different inclusion criteria.² Even with these risk stratification algorithms, some providers may continue to feel more comfortable obtaining CSF due to fear of missing meningitis in well-appearing, low-risk infants.

Bacterial meningitis, even in young infants, is rare. A recent meta-analysis estimated the general prevalence of meningitis in febrile neonates (regardless of risk stratification or bronchiolitis symptoms) in their first and second months of life were 1.2% (95% CI, 0.8%-1.9%) and 0.4% (95% CI, 0.2%-1.0%), respectively.³

Febrile infant risk stratification algorithms have high negative predictive values (NPVs) in ruling out meningitis. The Rochester criteria, which does not utilize CSF, has an NPV of greater than 98%.¹² A recent Pediatric Emergency Care Applied Research Network Clinical Prediction Rule has an NPV of 99.9% among febrile infants <60 days, using only absolute neutrophil count, urinalysis, and procalcitonin.¹⁵

Among the patients that are already a low risk, concomitant viral infections further decrease the pretest probability. Febrile infants with lab-confirmed respiratory viral infections are at lower risk for serious bacterial infections.^16,17 Multiple retrospective and prospective observational studies have demonstrated that low-risk patients with bronchiolitis symptoms are extremely unlikely to have bacterial meningitis.^8,18-22 A systematic review of 1749 febrile patients under 90 days of age with clinical bronchiolitis demonstrated no cases of meningitis.²³ Many of these studies included infants aged <28 days. Though the total number of neonates (<28 days) in all studies is somewhat unclear, it suggests that the cut-off to avoid an LP may be even lower.

Recent literature has advocated outpatient observation without an LP for low-risk infants as a cost-effective management tool,²⁴ and this is particularly true in patients with concomitant viral bronchiolitis.

Based on the latest data confirming the low prevalence of meningitis among all infants,³ the ability to identify low-risk infants based on risk stratification algorithms (Table), and the decreased prevalence of meningitis in patients with clinical bronchiolitis,²³ low-risk infants with bronchiolitis seem to have minimal, if any, risk of meningitis. Therefore, low-risk infants with bronchiolitis do not warrant an LP.

Importantly, LPs are not risk neutral. Their benefit versus harm should be weighed every time they are considered. Approximately 19% of LP attempts in infants under 90 days old are either traumatic or unsuccessful.²⁵ Infants aged 28 to 60 days with traumatic or unsuccessful LPs are more frequently hospitalized.²⁵ Increased hospitalizations are associated with higher costs.⁴ The majority of positive CSF cultures are deemed to be “contaminants” (87% in one study²⁶), but the positive result still leads to unnecessary further evaluation, hospitalization, repeated invasive procedures, and family distress.²⁷ These data further support refraining from pursuing an LP in low-risk infants with bronchiolitis.