A5V4d

Management by the paediatric specialist
PCT is not always 100%, it cannot be considered a gold standard and a normal PCT level could
conceivably falsely reassure clinicians. 165
Lower respiratory tract infection
Six of the studies looked at PCT as a marker for bacterial lower respiratory tract infection (LRTI) in
children. Of these, three found PCT to be more effective than either CRP or WBC in differentiating
bacterial from viral LRTI, whereas the other three studies found PCT to be of little value. This
inconsistency may have been due to difficulty and differences in the confirmation of bacterial LRTI
and also confounded by the use of antibiotics prior to measurement of PCT. PCT is known to fall
rapidly once a bacterial infection is appropriately treated compared with CRP, which will fall more
slowly and may even rise initially. 165
Fever without localising signs
In another EL II study, 178 the authors reported the results of PCT assessed in children with fever
without localising signs. Children treated with antibiotics during the preceding 2 days were excluded.
PCT was more sensitive (93% versus 79%) but less specific (74% versus 79%) than CRP for
predicting SBI (bacteraemia, pyelonephritis, lobar pneumonia and meningitis) in children with fever
without apparent source.
In addition to this systematic review, 165 one prospective EL II cohort study 167 studied 72 children 1–
36 months old with fever without apparent source. Eight (11.1%) children had SBI (one pneumonia,
two meningitis, four septicaemia/occult bacteraemia, two pyelonephritis), In identifying SBI in this
group, PCT at a cut-off value of 2 ng/ml showed a sensitivity of 50% and a specificity of 85.9%. In
comparison, at a cut-off of 50 mg/litre, CRP showed a sensitivity and specificity of 75% and 68.7%
respectively, while the Yale Observation Score had a sensitivity of 87.5% and specificity of 67.2%.
Chest X-ray
The diagnostic performance of chest X-ray in children with fever without apparent source (FWS) in
relation to WBC is described above. In addition, one EL 1b SR 179 and one EL II prospective cohort
study 180 were found that examined the diagnostic performance of chest radiography in differentiating
bacterial and viral pneumonia in children.
The SR looked at five studies which used credible reference standards for identifying bacterial and
viral infection. The authors considered identification of a bacterial pneumonia to be a positive test and
of a viral pneumonia to be a negative test. As a result of heterogeneity in the studies, the authors
could not report on comparable measures of diagnostic accuracy for each of the five studies. Rather,
the researchers calculated likelihood ratios (LRs) for each study, as a measure of clinical usefulness
of the chest X-ray. Commenting that LRs between 0.5 and 2.0 are rarely clinically useful, they
reported no LRs outside these levels in the studies reviewed. The authors concluded that no clinically
useful degree of accuracy had been demonstrated with regard to differentiating bacterial from viral
pneumonia using chest radiography.
In an EL II study 180 of children admitted to hospital with community-acquired pneumonia, those with
bacterial pneumonia had a significantly higher incidence of alveolar infiltrates compared with those
with exclusively viral disease (72% versus 49%, P = 0.001). In children with exclusively interstitial
infiltrates, half had bacterial infection and half viral.
Evidence summary
In children older than 3 months with fever without apparent source who appear well, 5% will have a
bacterial infection, likely to be UTI or pneumonia. Occult bacteraemia is not often seen in the UK and
is likely to decrease with the introduction of the universal pneumococcal vaccination. The currently
available tests (CRP, PCT and WBC) do not improve the detection of SBI in this group, compared
with features from the Yale Observation Score (YOS).
WBC and ANC perform less well than either CRP or PCT in helping to identify the presence of SBI. A
combination of temperature > 39°C and a WBC.> 20 × 10 9 /litre does, however, have a high specificity
for occult pneumonia. Evidence is conflicting regarding the performance of chest radiography in
differentiating bacterial and viral pneumonia in children but, at best, it has limited clinical usefulness.
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