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Evaluation of fever in infants less than 8 weeks old
Insights
Fever in infants under 8 weeks can indicate serious infection. Clinical appearance is a key factor in diagnosing bacteremia or bacterial meningitis, especially in younger infants.
Area of Science:
- Pediatrics
- Infectious Diseases
- Neonatology
Background:
- Fever in hospitalized infants under 8 weeks necessitates careful evaluation for serious bacterial infections.
- Previous studies highlight the challenges in diagnosing bacteremia and bacterial meningitis in this age group.
Purpose of the Study:
- To evaluate clinical and laboratory predictors of bacteremia or bacterial meningitis in febrile infants younger than 8 weeks.
- To assess the correlation between season, sex, fever height, ESR, WBC count, and neutrophil ratios with positive blood or CSF cultures.
Main Methods:
- Retrospective analysis of 342 hospitalized infants (<8 weeks old) with fever.
- Evaluation of clinical presentation (septic appearance vs. non-septic) and laboratory markers (WBC, immature to total neutrophil ratio, ESR).
- Prospective assessment of clinical impression in a subset of infants.
Main Results:
- Bacteremia or bacterial meningitis was identified in 5% of infants.
- No significant correlation found between season, sex, fever height, or ESR and bacterial recovery.
- Low WBC counts and elevated immature to total neutrophil ratios showed significant correlation but low sensitivity.
- Bacteremia was more common in infants <4 weeks (8%) than older infants (2.9%).
- Prospectively, infants with a septic appearance were more likely to have pathogens detected (4/36) than those without (0/61).
Conclusions:
- Clinical assessment, particularly the presence of a septic appearance, is a crucial factor in identifying febrile infants at risk for bacteremia or bacterial meningitis.
- Laboratory markers like WBC and neutrophil ratios have limited sensitivity for diagnosing these infections in this population.
- Younger infants (<4 weeks) are at higher risk for bacteremia.
Abstract:
We evaluated fever in 342 hospitalized infants less than 8 weeks of age. Sixteen infants (5%) had bacteremia or bacterial meningitis. Fifty-two percent of the infants were admitted during the months of July through September. We found no significant relationship between season, sex, height of fever, or erythrocyte sedimentation rate and the recovery of bacteria from the blood or CSF. A WBC less than or equal to 5,000/cu mm or a ratio of immature to total neutrophils greater than or equal to 20% correlated significantly with bacteremia or bacterial meningitis, though the sensitivities of these tests were unacceptably low. Prospectively, of 61 infants whose clinical appearance did not suggest sepsis, none had bacterial pathogens in the blood or CSF, whereas four of 36 infants with a septic appearance did have pathogens. Recent investigations support the initial clinical impression as important in assessing these febrile infants. We found that bacteremia is more likely to occur in infants less than 4 weeks of age (8%) than in the older infants (2.9%).