Investigating suspected early-onset sepsis

OSCE stationVivaEarly-onset sepsis

A viva on which tests diagnose early-onset sepsis, which do not, and when to perform a lumbar puncture.

Questions

1. Which test makes the diagnosis of early-onset sepsis, and what practical point improves its yield?

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   • Blood (or CSF) culture.
   • Paediatric blood culture bottles generally require a minimum of 1 mL of blood for optimal recovery of organisms.

2. Which tests does the AAP say cannot diagnose early-onset sepsis?

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   • A complete blood count, CRP, surface cultures, gastric aspirate analysis and urine culture.

3. What are the roles and limits of the white cell count and CRP?

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   • CPS: white cell indices or a single CRP should not be used routinely as screening or diagnostic tests, nor to exclude EOS.
   • Predictive ability improves after 4 hours of age (for example, a likelihood ratio of 115 for an absolute neutrophil count below 1 × 10⁹/L).
   • AAP: single CRP or procalcitonin values after birth are neither sensitive nor specific; consistently normal values over the first 48 hours are associated with the absence of EOS.
   • NICE: do not use CRP results alone to decide on starting, continuing or stopping antibiotics.

4. When should a lumbar puncture be performed, and why might it be needed even if the blood culture is negative?

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   • NICE: if it is safe to do so, when there is a strong clinical suspicion of infection or signs suggesting meningitis.
   • AAP: when blood culture confirms EOS, if not already done; not if it would compromise the baby or delay antibiotics.
   • CPS: 8% to 40% of infants with early-onset meningitis have negative blood cultures.

Based on: American Academy of Pediatrics clinical reports on early-onset sepsis (Pediatrics, 2018); Canadian Paediatric Society statement (2017); NICE guideline NG195, Neonatal infection: antibiotics for prevention and treatment (2021, last updated May 2026).