The Role of C-Reactive Protein in the Evaluation and Management of Infants With Suspected Sepsis

Joan M. Hengst, RNC, MSN, ARNP


Adv Neonatal Care. 2003;3(1) 

In This Article

Diagnostic Testing and Sepsis

The infant's birth weight, chronologic, and gestational age at the onset of sepsis also has an impact on the expected mortality rate.[2,3] Between 5% and 50% of infants with early-onset sepsis will succumb compared with a mortality rate of 10% to 20% with late-onset sepsis.[2,3,4,5,6] The rate of sepsis in term infants is 0.8 cases per 1,000 live births, and the mortality rate is 2.3%.[7] Two or more maternal risk factors escalate the risk to 4% to 5%.[8]

Low-birth-weight (LBW) infants are at the highest risk for both early- and late-onset neonatal sepsis.[4,5] This is caused, in part, by an immature, inexperienced immune system; a fragile cutaneous barrier; and a prolonged hospital stay with increased exposure to the neonatal intensive care unit (NICU) environment, including various invasive devices and procedures.[3,4,5,9,10] A large prospective National Institute of Child Health and Human Development (NICHD) Neonatal Research Network study of very low-birth-weight (VLBW) infants reported 19 cases of early-onset sepsis per 1,000 live births and 25 cases of late-onset sepsis per 1,000 live births in infants weighing between 401 and 1,500 g.[5] Fifty percent of infants weighing between 405 and 750 g developed late-onset sepsis.[4]

Infants who present with clinical signs of infection are evaluated with a variety of diagnostic tests, commonly referred to as a sepsis workup, and treatment with broad-spectrum antibiotics is initiated until a definitive diagnosis can be made.[3,11,12,13,14] Isolation of microorganism(s) from one or more blood cultures is the gold standard to establish a definitive diagnosis of neonatal sepsis.[12,13,15]

The sole use of blood cultures to diagnose neonatal infection has a number of limitations. It may take 24 to 72 hours to obtain culture results.[16,17] The sensitivity of blood cultures may be impaired by exposure to intrapartum antibiotics, which are administered to 15% to 40% of mothers in labor.[5,7,18] Intrapartum antibiotic exposure can result in a partially treated infant, delaying the onset of clinical signs and symptoms of infection and further complicating the expedient definitive diagnosis of early-onset sepsis in the infant. With the development of multiple drug-resistant bacteria and the cost of therapy with multiple antibiotics, the ability to diagnose or rule out sepsis is an essential tool to limit inappropriate antibiotic exposure.[13,19,20,21,22]

Over the last decade, a variety of laboratory tests have been developed to enhance the early and accurate identification and treatment of infants with suspected sepsis.[12,23,24,25,26,27] Common laboratory tests include the following:

  • White blood cell count (WBC) with differential

  • Calculation of the immature to total neutrophil (I:T) ratio and absolute neutrophil count (ANC)

  • Platelet count

  • Erythrocyte sedimentation rate

  • C-reactive protein (CRP)[3,12,24,26,27]

Although these tests are readily available and provide useful information, none of them has been found to be absolutely reliable in detecting all septic infants; therefore, they cannot be considered diagnostic.[3,12,13,25]


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