C-reactive protein alone or combined with cardiac troponin T for risk stratification of respiratory intensive care unit patients

Abstract

Background: Mortality is high among patients admitted to intensive care units (ICUs). Several prognostic markers have been described in such patients, but the literature contains no data comparing C-reactive protein (CRP) and cardiac troponin T (cTn-T), nor of a combination of CRP and cTn-T in the same patient group in the ICU.

Methods: This was a retrospective electronic data review of patients who presented to the emergency department for respiratory reasons between December 2007 and December 2009 and in whom CRP and cTn-T levels were measured. Patients with a diagnosis of pulmonary embolism and acute coronary syndrome were excluded. We recorded demographics, chronic diseases, admission diagnosis, Simplified Acute Physiology Score II (SAPS II), ICU stay, and CRP and cTn-T concentrations.

Results: We included the records of 158 patients. Mean ICU stay was 9.9 days (range 1-65 d), and mean hospital stay was 14.1 days (range 1-72 d). For predicting mortality, receiver operating characteristic analysis gave a CRP cutoff value of ≥ 10 mg/dL, and a CTn-T cutoff value of ≥ 0.01 ng/mL. For CRP the mortality area under the curve was 0.691 (95% CI 0.608-0.775), the sensitivity was 65%, and the specificity was 70%. For cTn-T the mortality area under the curve was 0.733 (95% CI 0.655-0.812), the sensitivity was 78%, and the specificity was 56%. Of the patients who died, 65% had CRP ≥ 10 mg/dL and 78% had cTn-T ≥ 0.01 ng/mL. On multivariable regression analysis, CRP ≥ 10 mg/dL was associated with 6.6-fold higher (95% CI 1.7-21.3) ICU mortality. There was no advantage for models that combined CRP and cTn-T. CRP alone was more valuable in predicting ICU mortality than in combination with troponin or SAPS II.

Conclusions: Elevated CRP is an independent early prognostic marker of mortality risk in ICU patients. We suspect that a CRP-based prognosis strategy may be useful.