Which lab findings are characteristic of neonatal sepsis?

Updated: Jun 13, 2019
  • Author: Nathan S Gollehon, MD, FAAP; Chief Editor: Muhammad Aslam, MD  more...
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Levels of CRP, an acute-phase protein associated with tissue injury, are elevated at some point in 50%-90% of infants with systemic bacterial infections. [44] CRP levels rise secondary to macrophage, T-cell, and adipocyte production of interleukin (IL)–6. This is especially true of infections with abscesses or cellulitis of deep tissue.

CRP levels usually begin to rise within 4-6 hours of the onset of infection, become abnormal within 24 hours of infection, peak within 2-3 days, and remain elevated until the inflammation is resolved. The CRP level is not recommended as a sole indicator of neonatal sepsis but may be used as part of a sepsis workup or as a serial study during infection to assess the response to antibiotics, determine the duration of therapy, or identify a relapse of infection.

Immunoglobulin M (IgM) concentration in serum may be helpful in determining the presence of an intrauterine infection, especially if the infection has been present for some time. Elevated IgM levels in umbilical cord sera suggest intrauterine infection. The clinical availability of such testing and access to timely results limits this assay’s utility.

Evidence on the use of infection markers such as CD11b, soluble CD14 subtype, CD64, IL-6, IL-8, IL-10, and granulocyte-colony stimulating factor (G-CSF) for evaluation of sepsis in neonates shows that they may be helpful as adjunctive tests. [45, 46, 47, 48] Their value may be further enhanced by performing serial measurements and using combinations of tests. At present, however, the consensus is that these tests should not be used alone to determine the need for antibiotic therapy, although in some cases they may prove useful in determining when to stop antibiotic therapy.

Levels of other acute-phase reactants (eg, procalcitonin and serum amyloid) are often elevated with the onset of sepsis. Procalcitonin, a pro-peptide of calcitonin produced in monocytes and in the liver, may be more sensitive than CRP. It is more specific to bacterial infection than viral infection. Levels of procalcitonin can be elevated in infants with respiratory distress syndrome and in infants of diabetic mothers, and it should be used in conjunction with the entire clinical situation and not as a single determinant of treatment initiation or duration. Procalcitonin may be used in combination with other acute-phase reactants, such as CRP. [19, 49, 50, 51]

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