Relationship of Fever Magnitude to Rate of Serious Bacterial infections in Infants Aged 4-8 Weeks

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Abstract
We correlated the height of fever with underlying infectious etiology in 683 consecutive febrile infants aged four to eight weeks who received outpatient evaluation for sepsis during a five-year period. The relative number of infants with fever was inversely proportional to fever height, as 51 % had a temperature 38.1 - 38.9°C, 45% had a temperature 39 - 39.9°C, and 4% had a temperature >40°C [hyperpyrexia]. There were 34 cases of serious bacterial infections [SBI], including 16 cases of urinary tract infection, 8 cases of bacteremia, 6 cases of bacterial meningitis, and 4 cases of Salmonella enteritis. The rate of SBI increased in direct proportion to fever height, being 3.2% in those with a temperature 38.1-38.9°C, 5.2% in those with a temperature 39-39.9°C, and 26% in those with a temperature >40°C. The 6.8% rate of SBI in those with fever >39°C was significantly greater than the 3.2% rate in those with fever <39°C [p <0.035]; and the 26% rate of SBI in those with hyperpyrexia was significantly greater than the 4.1 % rate in those with fever <40°C [p <0.000004]. In identifying those with SBI, the presence of hyperpyrexia had a sensitivity of 21 %, specificity of 97%, positive-predictive value of 25%, and negative-predictive value of 96%. The rate of SBI in febrile infants aged four to eight weeks is proportional to the height of fever documented at the time of evaluation; yet the predictive-value of hyperpyrexia in identifying individual infants with SBI is low. It is important that all febrile infants aged four to eight weeks receive complete evaluation for sepsis, regardless of height of fever.