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Although SBI is still prevalent in this age group, it is much less common than neonates 0 to 2 months of age. Previously, all children up to 3 months of age would receive a septic workup. However, a prospective study looking at 427 infants 57-180 days old found the rate of SBI to be equivalent to older age groups. Of note their risk of UTI was still high 10.3 percent, however their risk of bacteremia was only 0.9 percent and they had no cases of bacterial meningitis. Given these findings it appears pertinent to still have a high incidence of suspicion for UTI, but routine serum labs are unwarranted.
In addition, with such low rates of meningitis and bacteremia cost-effectiveness research has shown that clinical judgment was more useful in selecting at risk patients who would benefit from laboratory testing.
Classically febrile children have been risk stratified according to age, with 3 - 36 months containing the non-verbal or immature infant and toddler. With the advent of conjugated vaccines and further literature looking at the risk of infants beyond 8 weeks, we advocate for the lower age limit to start at 2 months.
Fever in this age group is defined by most sources as greater than 38 C (100.4 F) by rectal or core temperature. Infrared thermometers have become much more popular in recent times however they are only 53 percent sensitive detecting rectal temperatures greater than or equal to 38 C and 27 percent sensitive in detecting rectal temperatures greater than or equal to 39 C (102.2 F). Infrared and other non-invasive temperature readings must be taking in context of their sensitivities and repeat core temperature readings are usually necessary.
Patients with preexisting conditions or risk factors are at much higher risk for SBI. This pathway is not designed to assess the individual risk factors of these patients.
The clinical assessment in children with fever is important as it often gives clues to patients at high risk of SBI. Common diagnoses in this age for patients with fever include viral syndromes, acute otitis media, UTI, pneumonia and soft tissue infections. Less than 1 percent of these patients will have meningitis and bacteremia (depending on their vaccination status). Non-infectious diseases such as oncologic or rheumatologic diseases also present in this age group and risk factors for these disorders should be evaluated on H&P.
Of note, teething is often blamed for fevers in this patient population; however it is unlikely that fevers > 38.5 C (101.3 F) are related to teething.
Patients in this age group with hyperpyrexia are at much higher risk with 18.4 percent of them having an SBI. This included high rates of bacteremia, but not meningitis without meningeal signs. Because of this, patients with hyperpyrexia should be worked up with serum and urine studies, given empiric antibiotics and admitted.
Fever > 38.3 C (101 F) daily for 7 days represents fever of unknown origin and places patients in specific risk patterns for infectious and non-infectious disorders. Although a majority of these patients have common disorders presenting in uncommon ways, they deserve special attention and their own pathway.
In the preconjugate vaccine era the risk of occult bacteremia was ~5 percent in children with fever without a source, T-max > 39 C and serum WBC >15k mm3. The majority of these cases were caused by Streptococcus pneumoniae (50 - 90%) and Haemophilus influenzae (3 - 25%) followed by Salmonella species and Neisseria meningitides.
Although herd immunity decreases the risk of infection in patients currently it is likely that incompletely immunized patients have a greater than 1 percent risk of occult bacteremia (when there is no source of fever) if their fever is > 39 C (102.2 F). In a prospective study by Carstairs, et al. that separated out the immunized vs. incompletely immunized after PCV7. The unimmunized group had a bacteremia rate of 13/550 (2.4%); all positive cultures were with S. pneumoniae. In the immunized group, the rate of bacteremia with S. pneumoniae was 0/883 (0%) while the rate of bacteremia with other pathogens was 2/883 (0.23%; both patients also had urinary tract infections).
A clinical effectiveness study looked at these risks in the post vaccine era and determined that CBC plus blood culture plus antibiotics were cost effective when the rate of pneumococcal bacteremia was > 1.5 percent and lost effectiveness when the rate went below 0.5 percent.
Because of this, the AAP and ACEP have recommended a bacteremia workup and treatment of those patients at high risk with antibiotics.
There is no standard definition of "incomplete immunization" in children in this population. Different studies have used between 1 and 3 doses of HIB and PCV as their cutoff. It should be noted that a large majority of these studies, even with 1 dose of conjugated vaccine, saw a marked decrease in the incidence of occult bacteremia compared to the preconjugate vaccine era. At least one study Benito-Fernandez J, et al. found an increase rate of occult bacteremia in patients with less than 2 conjugated vaccines. For PCV, a single does has been shown to confer immunity in up to 75 percent of patients and a second dose up to 95 percent (and very low risk for occult bacteremia). Given that bacteremia in this patient population is a serious condition (and prone to progress to meningitis), we set our definition at 2 weeks after at least 2 sets of both HIB and PCV.
In addition, patients with petechial rash or those appearing ill with concomitant UTI or diarrhea/gastroenteritis are often included in the high risk group of patients requiring CBC/blood culture and potential antibiotics.
Many studies have used the CBC as a risk stratification tool. Newer biomarkers and acute phase reactants (C-reactive protein (CRP) and procalcitonin (PCT)) have been evaluated as screening tools for SBI. RP less than 20 mg/L and PCT less than 0.5 ng/ml were correlated with a less than 5 percent risk of SBI. CRP greater than 80 mg/L and PCT greater than 2 ng/ml were correlated with a greater than 72 percent of SBI. Combinations were even more sensitive and specific. It is still unclear in the literature what the role for biomarkers should be in evaluating children with fever without a source. Most providers believe than they may play a contributing role, but should not be used as the sole determining factor for decision.
Given the unclear use of these tests they are currently left off of the pathway.