Early identification of intensive care unit-acquired infections with daily monitoring of C-reactive protein: a prospective observational study

Introduction Manifestations of sepsis are sensitive but are poorly specific of infection. Our aim was to assess the value of daily measurements of C-reactive protein (CRP), temperature and white cell count (WCC) in the early identification of intensive care unit (ICU)-acquired infections. Methods We undertook a prospective observational cohort study ( 14 month). All patients admitted for >= 72 hours ( n = 181) were divided into an infected ( n = 35) and a noninfected group ( n = 28). Infected patients had a documented ICU-acquired infection and were not receiving antibiotics for at least 5 days before diagnosis. Noninfected patients never received antibiotics and were discharged alive. The progression of CRP, temperature and WCC from day - 5 to day 0 ( day of infection diagnosis or of ICU discharge) was analyzed. Patients were divided into four patterns of CRP course according to a cutoff value for infection diagnosis of 8.7 mg/dl: pattern A, day 0 CRP > 8.7 mg/dl and, in the previous days, at least once below the cutoff; pattern B, CRP always > 8.7 mg/dl; pattern C, day 0 CRP = 8.7 mg/dl and, in the previous days, at least once above the cutoff; and pattern D, CRP always <= 8.7 mg/dl. Results CRP and the temperature time-course showed a significant increase in infected patients, whereas in noninfected it remained almost unchanged ( P < 0.001 and P < 0.001, respectively). The area under the curve for the maximum daily CRP variation in infection prediction was 0.86 (95% confidence interval: 0.752 - 0.933). A maximum daily CRP variation > 4.1 mg/dl was a good marker of infection prediction ( sensitivity 92.1%, specificity 71.4%), and in combination with a CRP concentration > 8.7 mg/dl the discriminative power increased even further ( sensitivity 92.1%, specificity 82.1%). Infection was diagnosed in 92% and 90% of patients with patterns A and B, respectively, and in only two patients with patterns C and D ( P < 0.001). Conclusion Daily CRP monitoring and the recognition of the CRP pattern could be useful in the prediction of ICU-acquired infections. Patients presenting maximum daily CRP variation > 4.1 mg/dl plus a CRP level > 8.7 mg/dl had an 88% risk of infection.