Neonatal Sepsis Risk Stratification: Role of Serial Inflammatory Markers

Neonatal sepsis can progress quickly, yet many newborns investigated for infection will never develop a confirmed bacterial illness. The central clinical task is to identify babies who need immediate treatment while avoiding unnecessary antibiotic exposure, prolonged admission and disruption to early feeding and bonding. In this setting, inflammatory markers are most useful when they support a broader assessment rather than replace it.

A single C-reactive protein (CRP), procalcitonin (PCT) or white cell count offers only a snapshot. Newborn physiology changes rapidly during the first days of life, and the timing of a blood test can strongly influence its result. Serial testing adds information about direction and pace: a marker that remains low, falls, or rises steadily has a different meaning from an isolated borderline value.

For Australian maternity and neonatal services, practical decisions must also reflect local resources. A tertiary unit in Sydney, Melbourne or Brisbane may have rapid laboratory access and neonatal infectious diseases support, while a rural hospital may need to arrange transport before repeat results are available. Clear escalation pathways, good communication with families and careful documentation are therefore as important as the assay itself.

Why Risk Changes Over Time

Neonatal sepsis risk is shaped by gestational age, birth circumstances, maternal infection, rupture of membranes, intrapartum fever, colonisation status and the infant’s clinical course. Early-onset infection often presents within the first 72 hours, while late-onset infection is associated with hospital exposure, central lines, prematurity and other vulnerabilities. A newborn who appears well at birth may become symptomatic later, so risk assessment must be repeated.

Clinical observation remains the first and most frequent assessment. Abnormal temperature, increasing oxygen need, poor perfusion, apnoea, feeding intolerance, lethargy, glucose instability or an altered level of responsiveness should carry more weight than a reassuring laboratory number. In a busy Australian nursery, the handover between midwives, neonatal nurses and medical staff should state whether signs are improving, stable or evolving, rather than simply recording that the baby is “well”.

Blood culture remains the reference test for bloodstream infection, although its reliability depends on adequate volume, correct collection and antibiotics given before sampling. A negative culture does not automatically settle the case if the newborn deteriorates. Conversely, a well-appearing infant with negative cultures and consistently reassuring examinations may be exposed to avoidable treatment if antibiotics continue solely because of an early, non-specific marker.

Choosing Markers And Timing

CRP is widely available and familiar to Australian laboratories, but it usually rises several hours after an inflammatory stimulus. A low initial CRP therefore has limited value immediately after birth. Repeat measurement after an appropriate interval can be more informative, particularly when paired with clinical improvement and a sterile blood culture. The exact timing should follow the neonatal unit’s protocol rather than an arbitrary universal schedule.

Procalcitonin may increase earlier than CRP, but it also follows a physiological postnatal pattern, especially during the first 48 hours. Gestational age, respiratory distress, maternal factors and non-infectious inflammation can affect interpretation. Interleukin-6 and other cytokines may rise early, although availability, cost and assay standardisation vary. Full blood count indices, including neutrophil count and immature-to-total neutrophil ratio, can contribute context but have limited sensitivity when used alone.

Local validation matters. A marker pathway developed in a large Melbourne neonatal intensive care unit may not transfer directly to a small regional service with different patient populations, laboratory turnaround times and transfer thresholds. Hospitals should define which tests are available, who reviews abnormal or discordant results, and how results are communicated during overnight shifts, weekends and public holidays.

Interpreting Trends Alongside Clinical Signs

The most useful pattern is usually concordance. A clinically stable baby with negative cultures, improving observations and low or falling CRP has a stronger case for antibiotic cessation than a baby whose marker is low but who has worsening respiratory effort or perfusion. A rising value should trigger a fresh examination and review of cultures, vascular access, lungs, abdomen, skin and other possible infection sources.

Serial results should be read as trajectories rather than isolated cut-offs. A modest rise may be significant if it is persistent and accompanied by new symptoms, while a high value may reflect a non-infectious event such as birth stress, meconium aspiration, surgery or tissue injury. The laboratory report should be interpreted with postnatal age, gestation and the clinical timeline visible to the treating team.

Decision-making should also account for the harms of both under-treatment and over-treatment. Delayed therapy in a genuinely septic newborn can lead to shock, meningitis or organ injury. Unnecessary antibiotics can alter the microbiome, increase medication exposure, encourage resistant organisms and prolong hospitalisation. A documented antibiotic review at a defined time—often around 24 to 48 hours, depending on the clinical picture and culture system—helps keep the balance explicit.

Applying Evidence In Australian Services

Australia’s geography creates different sepsis pathways. A newborn in inner-west Sydney may receive repeated tests within minutes of a concern, while a family in the Northern Territory or regional Western Australia may face retrieval to Darwin, Perth or another referral centre. In the latter setting, a trend that can be safely monitored locally must be distinguished from a result that should accelerate consultation and transport. Telehealth, retrieval networks and structured referral calls can support this process.

The local maternity model also affects observation. Rooming-in, skin-to-skin care and breastfeeding support are common priorities, but they require a practical monitoring plan when infection is being considered. Families should understand why observations and blood tests are repeated, what symptoms matter and when treatment may stop. Plain English explanations are essential for families from culturally and linguistically diverse communities, including those receiving care in major cities.

Follow-up matters when sepsis, prolonged antibiotics or prematurity affects feeding, development or parental confidence after discharge. Experience from neonatal follow-up clinics illustrates the value of structured post-discharge care, even though follow-up cannot substitute for appropriate acute treatment. Australian units can link neonatal review with lactation support, community nursing, Aboriginal Community Controlled Health Services and the family’s general practitioner.

Building A Reliable Clinical Pathway

A safe pathway makes the clinical question clear before ordering a marker: Is the team deciding whether to start treatment, whether to continue it, or whether a deteriorating baby needs broader investigation? Serial inflammatory markers are most valuable for the second question and as supporting evidence in the third. They are less reliable as a stand-alone screening tool in an asymptomatic newborn.

The pathway should specify when to collect a blood culture, which marker to use, when to repeat it and who is responsible for acting on the result. It should also record gestational age, postnatal age, antibiotic timing, clinical observations and any non-infectious explanation for inflammation. These details reduce misinterpretation when care moves between a birth suite, special care nursery, neonatal intensive care unit and retrieval team.

Practical recommendations include:

• Treat clinical deterioration as an emergency, regardless of a previously reassuring inflammatory marker.
• Obtain an appropriately collected blood culture before antibiotics whenever this will not delay urgent therapy.
• Use CRP, PCT or other tests according to a locally approved protocol that accounts for gestation and postnatal age.
• Schedule antibiotic review using culture results, examination findings and marker direction rather than a single threshold.
• Audit antibiotic duration, culture sampling, readmissions and confirmed sepsis to refine the pathway over time.

Reliable implementation depends on measurement and feedback. Units can review how often antibiotics are started for risk factors alone, how frequently treatment continues after negative cultures, and whether repeat testing changes management. The FAOPS 2020 congress site provides a reminder of the value of shared scientific discussion across perinatal and neonatal communities, particularly when services are adapting evidence to different clinical environments.

Australian neonatal teams can strengthen sepsis care by combining repeated examination, timely cultures, carefully timed inflammatory markers and transparent communication with families. Hospitals should adapt the approach to their laboratory capacity and referral geography, then review outcomes with clinicians, nurses, midwives, pharmacists and parents. Start by auditing the current pathway and agreeing on a clear, evidence-informed review point for every newborn receiving empirical antibiotics.