Diagnosis and follow-up of infections in intensive care patients: Value of C-reactive protein compared with other clinical and biological variables*

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Abstract
To evaluate diagnostic and prognostic values of C-reactive protein (CRP) dosage in critically ill patients. Prospective, observational study. Medical intensive care unit (ICU) in a university hospital. A consecutive series of 74 patients admitted to the ICU. CRP measurements at admission and every 4 days thereafter. At admission, 28 patients (38%) had microbiologically proven infections. Compared with uninfected patients, their mean ± sd CRP level was 191 ± 123 vs. 83 ± 91 mg/L (p < .0001), respectively, white blood cell count was 15.3 ± 7.5 vs. 11.4 ± 5.3 G/L (p = .01), and the systemic inflammatory response syndrome (SIRS) was present for 96% vs. 67% (p = .008). No threshold value could be identified to discriminate between these two populations. Multivariate analysis retained CRP and SIRS as the only variables independently associated with the presence of an infection. The combination of CRP ≥50 mg/L with SIRS was identified as the best model to diagnose infection at admission. This multivariate model performed better than temperature, CRP alone, and white blood cell count. Among the 28 infected patients, 10 recovered; CRP values decreased significantly in this population as compared with patients with persistent infection (−130 ± 110 vs. 12 ± 97 mg/L, respectively;p = .004). A CRP decrease ≥50 mg/L between admission and day 4 was the best cutoff value to diagnose recovery (sensitivity 89%, specificity 79%). CRP in combination with SIRS was useful to diagnose infection in ICU patients; a CRP decrease ≥50 mg/L between admission and day 4 was the best predictor of recovery.