A single test to rule out bacteria infection would be a lovely invention. But, in the absence of such, we’ll settle for a test to rule out serious bacterial infection. But, alas, procalcitonin – despite its sponsored proponents – is not that test.
This is a systematic review and meta-analysis pooling 2,317 patients from seven studies evaluating its use in detection of SBI in a neonatal population of less than 91 days of life. Most commonly, the discriminatory value reported used was 0.3 ng/mL, with five studies reporting this data and the other two providing this data upon request. All told, infants with PCT >0.3 ng/mL had a 42.7% prevalence of SBI, while those with PCT below the cut-off had a 12.5% prevalence.
So, this works out to a relative risk of 3.97 (95% CI 3.41 to 4.62) given a PCT greater than the cut-off. Unfortunately, a prior review of the “Rochester criteria” for infants aged 29 to 90 days noted this cohort of low-risk patients had a prevalence of SBI of only 2.7%, with a RR for SBI of 30.6 (95% CI 7.0-68.13). Noting 2.7% to be superior to 12.5% as a rule-out mechanism, it would seem prudent to retain the Rochester criteria rather than rely on PCT.
It may be reasonable to incorporate PCT into future decision instruments for risk-stratification, but such validated rules are not yet available.
“Use of Serum Procalcitonin in Evaluation of Febrile Infants: A Meta-Analysis of 2,317 Patients”
http://www.ncbi.nlm.nih.gov/pubmed/25281186