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

Limitations in the Use of CRP Levels in Infants

Many researchers have evaluated serum CRP for its predictive value in identifying infants with suspected sepsis. A CRP level measured at the onset of signs of infection has an overall sensitivity between 35% to 94% and a specificity between 60% and 96% in diagnosing sepsis.[11,15,25] These broad ranges reflect variations in the population studied and the definition of sepsis, as well as different evaluation strategies, differences in defining abnormal serum cutoff levels, various methods of measuring CRP, and the number and timing of samples collected. Each variation in approach can influence the sensitivity and specificity of CRP levels in identifying sepsis. Table 3 provides an overview of the findings of relevant studies.

The timing of CRP measurement(s) is critical to achieve the highest sensitivity. A single CRP level drawn early in the course of disease has a low sensitivity between 35% and 96% in detecting the presence or absence of infection because the sampling time may precede a measurable rise in CRP levels; this rise may lag 12 to 24 hours after the onset of symptoms.[11,15,20,22,26,49] It cannot be overemphasized that a single CRP level, obtained at the onset of illness, lacks sufficient sensitivity to be useful in prospectively excluding the diagnosis of sepsis.[11]

Further, serum CRP testing is not suitable as a sole diagnostic test in determining sepsis because it can be elevated for reasons other than infection. Increased CRP levels can occur in infants for up to 3 days of life from noninfectious causes.[23,29] The following factors have been reported to cause elevated CRP levels:

  • Maternal fever during labor[37,40]

  • Prolonged rupture of membranes[37,40]

  • Stressful delivery, fetal distress, or bot.[37]

  • Perinatal asphyxia/shock[26,37,40]

  • Periventricular and intraventricular hemorrhag.[26]

  • Pneumothorace.[26]

  • Meconium aspiration pneumonitis[15,26,37,40]

CRP is not considered accurate in the preterm population. Levels do not always rise above 10 mg/L in preterm infants or those infants with overwhelming sepsis, resulting in a false-negative test result.[19,23,49,56,57] Some authors hypothesize that the immature liver function of premature infants decreases their ability to generate and secrete CRP into the serum and/or there may be decreased ability of CRP to actually bind to phosphocholine and activate the complement system.[56]


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