Risk stratification tools that omit lumbar puncture accurately classified most well-appearing febrile infants with invasive bacterial infections as being at low risk, results of a recent study show.

The modified Philadelphia criteria were highly sensitive for risk stratifying febrile infants, in a recent validation study based on a large, multicenter sample, investigators report. No infants with bacterial meningitis were classified as low risk using the modified criteria, which do not include routine testing of cerebrospinal fluid (CSF). Two infants with bacterial meningitis, both younger than 28 days old, were classified as low risk using the Rochester criteria, which also avoid routine lumbar puncture, investigators reported.

“Our findings support the use of the modified Philadelphia criteria without routine CSF testing for febrile infants in the second month of life,” the investigators said in their report, published in Pediatrics.

However, to confirm the safety of omitting CSF testing in low-risk febrile infants older than 28 days, a prospective study will be needed, cautioned the researchers, led by Paul L. Aronson, MD, of the department of pediatrics at Yale University in New Haven, Conn.

Nevertheless, some clinicians do not automatically perform CSF testing in infants older than 28 days because of the rarity of bacterial meningitis in that age group, they said in the report.

The study by Dr. Aronson and colleagues was based on data for infants younger than 60 days of age seen in the emergency departments of 9 hospitals between July 2011 and June 2016. The final sample included 135 infants with invasive bacterial infections, including 118 who had bacteremia without meningitis and 17 who had bacterial meningitis, along with 249 matched febrile infant controls.

A total of 25 infants with invasive bacterial infections were classified as low risk by the Rochester criteria, and 11 of those were low risk by the modified Philadelphia criteria, investigators said.

Compared with the modified Philadelphia criteria, the Rochester criteria had a lower sensitivity (81.5% vs. 91.9%; P = 0.01) and a higher specificity (59.8 vs. 34.5%; P less than 0.001).

Out of the 11 infants deemed low risk per the modified Philadelphia criteria, none were diagnosed with bacterial meningitis. By contrast, 2 of the 25 infants who were low risk per the Rochester criteria had bacterial meningitis, and both were younger than or equal to 28 days of age. “Both of these infants would have been classified as high risk per the modified Philadelphia criteria,” Dr. Aronson and his coauthors said.

Based on the findings of this study, caution should be exercised in applying low-risk criteria to infants 28 days of age or younger, according to the investigators.

“Febrile infants discharged from the emergency department without CSF testing should have close outpatient follow-up,” they wrote.

Dr. Aronson and his coauthors reported that they had no relevant disclosures. One coauthor reported serving as an expert witness in malpractice cases involving evaluation of febrile children.

SOURCE: Aronson PL et al. Pediatrics. 13 Nov 2018. doi: 10.1542/peds.2018-1879).