[Factors predicting serious bacterial infections in febrile infants less than three months old: multivariate analysis].

Aim: To identify predictive factors of the presence of a serious bacterial infection (SBI) in febrile infants less than three months old.

Methods: Retrospective analysis of the medical files of 315 consecutive consultations of febrile infants less than three months old in the pediatric emergency department of a French hospital, with logistic regression multivariate analysis of the different criteria routinely considered and C-reactive protein (CRP).

Results: SBI were diagnosed in 79 (25.1%) infants, primarily urinary tract infections (71; 22.5%). One of these 79 children had pneumococcal meningitis but met the classical criteria for low risk of SBI: he died because antibiotics were not prescribed sufficiently early. Factors significantly associated with SBI were: male sex; temperature >38.5 degrees C and lasting >24 hours; poor general condition; absence of ear, nose and throat symptoms; high white blood cell count with >50% neutrophils; and serum CRP concentration >20 mg/l. Multivariate analysis entering all these items retained only the latter two (respectively, OR: 13.5, 95% CI: [6.5-28.2] and OR: 2.9; 95% CI: [1.3-6.3]). CRP <20 mg/l and <50% neutrophils had a negative-predictive value of 93.1% for the absence of SBI.

Conclusions: At present, no factor(s) is(are) able to predict with 100% accuracy the absence of SBI in febrile infants less than three months old. The risk of severe sequelae or death caused by untreated SBI would seem to justify the prescription of antibiotics until microbacterial culture results become available.