Sensitivity, Specificity, and Clinical Utility of CRP Levels
When combined with other tests, elevated CRP levels lend support to a diagnosis of sepsis while awaiting culture results.[15,20] Sepsis screening panels augment, but do not replace, a thorough history, physical examination, and other clinical data.[12,20,26] The use of combinations of tests, such as CRP, leukocyte indices, I:T ratios, elastase -proteinase inhibitor complexes, and IL-6, IL-8, and TNF levels, is under investigation.[12,24,39] Studies examining the use of 2 tests, serial CRP and IL-8 levels, in infants being evaluated for late-onset sepsis revealed that if both levels were elevated, a sensitivity of 93% to 100% and specificity of 80% to 83% was achieved. This adds to the current body of evidence supporting the use of a combination of tests, along with the infant's history and physical examination, to improve the overall sensitivity and specificity of tests used to identify infection.[7,26]
Infants suspected of sepsis often present with nonspecific subtle symptoms. They are treated initially with broad-spectrum antibiotics until culture results are available. As many as 20% to 30% of LBW infants are exposed to antenatal antibiotics;[5,7,21] 79% of these infants are started on antibiotics within 24 hours of birth.[7,11] Approximately 6% to 47% of infants with clinical signs of infection and a negative blood culture continue on antibiotics for an average of 2 to 5 days.[5,7]
A CRP level that returns to the normal range (<10 mg/L) may indicate that the duration of antibiotic treatment has been sufficient, allowing earlier discontinuation of antibiotics.[21,22,49] Several authors suggest that 2 CRP levels <10 mg/L have a negative predictive value of 99% in accurately identifying infants not infected or with a resolved infection.[11,21,49]
In the face of increasing numbers of resistant organisms to antibiotics. using serial CRP levels to identify infants not likely to be infected has the potential to decrease overuse of antibiotics and slow the rate of antimicrobial resistance.[4,5,11,29,49] CRP has a high predictive value when it remains normal 24 to 48 hours after the onset of signs of infection and is useful in retrospectively excluding the diagnosis of sepsis in infants receiving antibiotic therapy.[3,11,15,21,23]
Serial measurements of CRP levels drawn every 24 to 48 hours after the onset of signs of infection have an increased sensitivity between 78.9% and 98%, specificity of 84% to 97%, and a negative predictive value of 99% in detecting sepsis.[11,15,21,23,26] A high negative predictive value indicates that CRP levels drawn between 24 and 48 hours can identify infants who are unlikely to be infected.[11,15,22,26]
Adv Neonatal Care. 2003;3(1) © 2003 W.B. Saunders
Cite this: The Role of C-Reactive Protein in the Evaluation and Management of Infants With Suspected Sepsis - Medscape - Feb 01, 2003.