EVIDENCE-BASED ANSWER
Evidence from prospective and retrospective clinical trials suggests that for infants <2 months old, only those at high risk for serious bacterial infection by standardized criteria (eg, Rochester classification) require lumbar puncture (strength of recommendation [SOR]: B, based on prospective and retrospective cohort studies). However, expert opinion suggests lumbar puncture on all infants aged 0 to 28 days with suspected sepsis, and all infants aged >2 months who are to receive empiric antibiotics (SOR: C, based on expert opinion).
Evidence summary
Standardized clinical criteria (Table) exist to determine the risk of serious bacterial infection, which includes meningitis; of particular note, these criteria do not require cerebrospinal fluid examination. Infants aged <3 months who fall into the “high-risk” category or appear toxic have 21% probability of a serious bacterial infection, 10% probability of bacteremia, and 2% probability of bacterial meningitis.1 The “low-risk” infants have a correspondingly lower incidence of serious bacterial infection: the negative predictive value of the Rochester classification is 98.9% (95% confidence interval [CI], 97.2–99.6%).2
The negative predictive value for bacterial meningitis (a subset of serious bacterial infection) is even greater. Five studies applied the standardized criteria to febrile infants and monitored them for the development of serious bacterial infection, including meningitis. Two prospective cohort studies of outpatients aged 0 to 2 months used the Rochester criteria to assign infants to risk groups. They studied a total of 1294 infants; 659 (51%) were low-risk. None of the low-risk infants developed bacterial meningitis.2,3
One prospective cohort study of infants aged <1 month hospitalized for fever used a similar method for assessing risk, but added a C-reactive protein value <20 mg/L to criteria for low-risk. Of 250 infants studied, 131 (52%) were low-risk; none of these developed bacterial meningitis.4
A retrospective chart review of 492 infants aged <3 months who were hospitalized due to fever included 108 infants aged <1 month. Thirty percent (114) of the infants aged 1 to 3 months and 67% (72) of the younger infants underwent lumbar puncture at the discretion of the treating physician. All infants were retrospectively assigned to low- or high-risk groups for serious bacterial infection using the Rochester criteria. Of the 296 infants rated “low-risk,” none developed bacterial meningitis. Ten of these infants subsequently developed evidence of another bacterial focus (predominantly urinary tract infection).5
RECOMMENDATIONS FROM OTHERS
The American Academy of Pediatrics has not issued a clinical practice guideline or clinical report addressing this issue. An evidence-based guideline developed at Cincinnati Children’s Hospital Medical Center in 1998 recommends hospitalization and a full sepsis workup (including lumbar puncture) for infants aged <1 month, or infants aged 1 to 2 months who are high-risk.6
A clinical review-based guideline published in 1993 gives the same recommendations.7 The expert panel that devised this guideline emphasized a full sepsis evaluation (including cerebrospinal fluid cultures) for infants <28 days of age “despite the low probability of serious bacterial infections in this age group and the favorable outcome of the children managed to date with careful observation.” For low-risk infants aged 1 to 2 months, lumbar puncture is not necessary unless empiric antibiotics are given; having a cerebrospinal fluid culture prior to empiric antibiotics reduces the concern of partially treated meningitis in the case of clinical deterioration after hospital discharge.6,7
TABLE
How to identify infants at low risk of serious bacterial infection: Rochester Classification
| Febrile infants (temperature ≥38°C, 100.4°F) ≥60 days of age who meet all criteria are at low risk of serious bacterial infection: | |
|---|---|
| General health | Born at ≥37 weeks’ gestation |
| Did not receive perinatal or antenatal antibiotics | |
| Was not treated for unexplained hyperbilirubinemia | |
| Was not hospitalized in the nursery longer than the mother | |
| Has had no hospitalization since discharge | |
| No diagnosed chronic or underlying illnesses | |
| Physical findings | Appears well and nontoxic |
| No evidence of skin, soft tissue, bone, or joint abnormalities, or otitis media | |
| Laboratory findings | Peripheral total white blood cells 5,000–15,000/mm3 |
| Absolute band form leukocytes <1,500/mm3 | |
| Spun urine sediment <10 white blood cells per high power field | |
| Fresh stool smear <5 white blood cells per high power field | |
CLINICAL COMMENTARY
Evaluating fever in infants: judging the risks
Randy Ward, MD
Family Medicine/Psychiatry Residency, Medical College of Wisconsin, Milwaukee
The evaluation of the febrile infant is often fraught with anxiety. Physicians must balance the potentially devastating consequences of a missed serious bacterial infection with the desire to avoid unnecessary work-ups.
In the past, guidelines have had an extremely conservative viewpoint, essentially grouping all infants by age, and recommended an extensive inpatient work-up regardless of clinical status. The Rochester Criteria have provided guidelines for clinical risk stratification in this age group, allowing a more rational approach to the workup. The above data provide further useful guidance for the appropriate use of lumbar puncture in evaluation of these infants.