A5V4d

Evidence statements
Management by the paediatric specialist
The following definitions have been used when summarising the levels of sensitivity, specificity,
positive predictive value (PPV) and negative predictive value (NPV):
High – 90% and above
Moderate – 75% to 89%
Low – 74% or below
C-reactive Protein
Fifteen studies of moderate to very low quality examining different combinations of bacterial illness
were included in the review. The results showed that CRP has moderate sensitivity and specificity. A
level below 20 mg/ml was needed to maximise sensitivity and a level above 80 mg/ml is needed to
maximise specificity.
Procalcitonin
Ten studies of low to very low quality examining different combinations of bacterial illness were
included in the review. The results showed that PCT has moderate sensitivity and specificity. A level
below 0.5 ng/ml is needed to maximise sensitivity and a level above 2 ng/ml is needed to maximise
specificity.
Comparison of procalcitonin with C-reactive protein
Eight studies of low to very low quality comparing PCT and CRP were included in the review.
One study of very low quality evidence had a population with 23% prevalence of bacteremia,
pyeonephritis, pneumonia, bacterial meningitis, bone infection and sepsis. Procalcitonin showed low
sensitivity and moderate specificity at 0.5 ng/ml; low sensitivity and high specificity at 1 ng/ml; and low
sensitivity and high specificity at 2 ng/ml. C-reactive protein showed moderate sensitivity and low
specificity at 20 mg/l; low sensitivity and moderate specificity at 40 mg/l; and low sensitivity and high
specificity at 80 mg/l.
One study of low quality evidence had a population with 29% prevalence of bacteremia,
pyelonephritis, pneumonia, mastoiditis and retropharyngeal abscess. Procalcitonin showed high
sensitivity and low specificity at 0.5 ng/ml. C-reactive protein showed moderate sensitivity and
moderate specificity at 40 mg/l.
One study of low quality evidence had a population with 23.6% prevalence of bacteremia, meningitis,
sepsis, UTI, pneumonia, gastroenteritis and cellulitis. Procalcitonin showed low sensitivity and
moderate specificity at a cut-off of 0.5 ng/ml or more. C-reactive protein showed low sensitivity and
moderate specificity at a cut-off of 20 mg/l or more: it also showed low sensitivity and moderate
specificity at a cut-off of 30 mg/l or more.
One study of low quality evidence had a population with 16% prevalence of bacteremia, UTI,
pneumonia and bacterial meningitis. Procalcitonin showed moderate sensitivity and low specificity at
a cut-off greater than 0.2 ng/ml. C-reactive protein showed high sensitivity and low specificity at a cutoff
of 17.7 mg/l or more.
One study of very low quality evidence had a population with 11.1% prevalence of bacterial
pneumonia, bacterial meningitis, septicaemia and pyelonephritis. Procalcitonin showed moderate
sensitivity and low specificity with a cut-off greater than 500 ng/ml but it showed low sensitivity and
moderate specificity at a cut-off greater than 2000 ng/ml. C-reactive protein showed moderate
sensitivity and low specificity at a cut-off greater than 50 mg/l.
One study had a population with 0.6% prevalence of bacteremia and sepsis. Procalcitonin showed
moderate sensitivity and high specificity at a cut-off greater than 0.5 ng/ml. Evidence for this finding
was of low quality. C-reactive protein showed low sensitivity and low specificity at a cut-off greater
than 30 mg/l. Evidence for this finding was of very low quality.
One study of low quality evidence had a population with 3.2% prevalence of bacteremia. Procalcitonin
showed low sensitivity and moderate specificity at a cut-off of 2 ng/ml or more. C-reactive protein
showed low sensitivity and low specificity at a cut-off of 40 mg/l or more.
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2013 Update