For neonates with suspected sepsis, which lab and imaging studies are typically obtained to guide treatment?

• A. CBC with differential, blood cultures, CRP, procalcitonin, serum lactate, venous/arterial blood gas; CSF culture if indicated; chest radiograph; ultrasound or abdominal imaging if NEC suspected; urinalysis and culture.
• B. Only CBC and blood cultures.
• C. MRI brain only.
• D. Urinalysis and culture only.

Answer: (A)

When sepsis is suspected in a neonate, the goal is to rapidly identify infection, assess the baby's overall physiologic status, and locate the source so treatment can be targeted and adjusted as results come in. A broad initial workup accomplishes this by combining microbiologic data, inflammatory and metabolic markers, and imaging to reveal organ involvement.

Blood cultures and a complete blood count with differential are fundamental because they document bacteremia and show how the immune system is responding, which helps estimate severity even before culture results return. Inflammatory markers such as C-reactive protein and procalcitonin add information about the likelihood of an infectious process and help gauge response to therapy over time. Evaluating metabolic and perfusion status with serum lactate and a venous or arterial blood gas provides insight into tissue oxygenation, acid-base balance, and the extent of metabolic stress, guiding fluid and perfusion management.

If there is concern for meningitis, obtaining cerebrospinal fluid culture (and analysis) is important to detect CNS infection and tailor antibiotic therapy accordingly. Imaging complements the lab data by identifying sources or consequences of infection: chest radiography screens for pneumonia or other lung pathology, and abdominal imaging (often ultrasound) is used when conditions like necrotizing enterocolitis are possible. Urinalysis with culture screens for urinary tract infection, a common sepsis source in neonates.

All of these pieces together help determine which antibiotics to start and for how long, guide supportive care decisions, and allow monitoring of the infant’s response to treatment.