Plasma procalcitonin and C-reactive protein in acute septic shock: clinical and biological correlates.

OBJECTIVE: To determine the relationship between plasma procalcitonin (PCT) levels, C-reactive protein (CRP), white blood cell count (WBC), ionized calcium (Ca2+), and patient outcome; and to compare the diagnostic and prognostic information provided by PCT and by CRP.
DESIGN: Prospective, observational study.
SETTING: Intensive care unit. PATIENTS: Fifty-three patients with septic shock, consecutively diagnosed according to consensus guidelines.
INTERVENTIONS: None.
MEASUREMENTS AND MAIN RESULTS: Blood was sampled at diagnosis and 24 and 48 hrs later and in a subgroup (n = 23) after 120 hrs. PCT was measured with LUMItest and CRP with Vitros slides. Ca2+ was calculated according to McLean-Hastings from calcium and protein levels on Vitros. In all 53 patients, PCT and CRP were elevated (>0.5 ng/mL and >10 mg/L, respectively) within 24 hrs after diagnosis. Nonsurvivors (n = 25) were older (p <.001) and had higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores (p =.02) at diagnosis but did not differ in sepsis etiology, medical history, sex ratio, levels of PCT, CRP, and Ca2+, or WBC count at any time point. Using logistic regression, initial PCT levels were correlated with CRP values (p =.001) and APACHE II score (p <.05), but not with age, gender, Ca2+ levels, survival, or type of pathogen. Within 48 hrs, however, PCT levels decreased more frequently from baseline in survivors than in nonsurvivors (80% vs. 41%, p <.05). Likewise, CRP levels decreased more often in survivors (100% vs. 64%, p <.05) but only at 120 hrs.
CONCLUSIONS: PCT levels were correlated with the severity of disease at onset (APACHE II) and inflammation (CRP) but not with Ca2+ levels. Inaugural PCT or CRP levels per se poorly predicted outcome but decreasing levels were associated with a higher probability of survival. In this respect, PCT was found to be an earlier marker than CRP.