Objective: To evaluate the diagnostic contribution of the investigation of procalcitonin (PCT) in critically ill patients. To compare the values of PCT with the values of other acute phase reactants. We also wanted to evaluate the relation between quantitative and semiquantitative methods of PCT investigation. Methods: In 45 patients a total of 188 investigations of the following parameters were carried out from plasma: PCT, C-reactive protein (CRP), orosomucoid, alpha1-antitrypsin, prealbumin, cholinesterase, count of leukocytes and indexed Quick’s test (INR). In relation to the PCT and CRP values the investigations of hemoculture, the positivity of bacteriological findings, the presence of apparent infect and Systemic Inflammatory Response Syndrome (SIRS) were analyzed and the score Systemic Organ Failure Assessment (SOFA) was evaluated. PCT was set by immunoluminometric analysis by means of LUMItest-PCT-kit, produced by B.R.A.H.M.S. Berlin and parallely by quick, semiquantitative PCT-Q test by the same producer. Results: In accordance with the negativity or positivity of the apparent infect and of bacteriological findings, the significantly higher values of PCT were found in the group with positive results. There were no significant differences in CRP values. No statistically significant difference was stated between positive and negative hemoculture investigations. In subgroups, resulting after the division of the set into SIRS negative (N = 52) and SIRS positive (N = 142), the values (medians, lower and upper quartils) were as follows: PCT (µg/l) 0.43 (0.3; 0.78) and 0.92 (0.5; 2.8), (P < 0.01), CRP (mg/l) 115 (70; 176) and 136 (83; 234), (P < 0.05). Findings in sepsis were divided after its stage as follows: sepsis (N = 36), severe sepsis (N = 50) and septic shock (N = 48). The PCT (µg/l) values in these groups were 0.5 (0.4; 0.91), 1.17 (0.6; 5.45) and 1.7 (0.5; 4,5). The CRP (mg/l) values were 108 (64; 161), 169 (64; 260) and 151 (102; 250). Significant difference was found between sepsis and severe sepsis (for PCT: P < 0.01, for CRP: P < 0.05) and between sepsis and septic shock (for both parameters: P < 0.01). For relations between the same stages of sepsis the INR values, the SOFA score and the body temperature differed on 1% level. Neither the values of orosomucoid nor alpha1-antitrypsin contributed to differentiation of sepsis. The comparison of quantitative and semiquantitative methods for PCT estimation documented the reliability of the latter one in the differention of findings in reference values from the elevated ones. Conclusion: PCT is a useful parameter extending the possibilities of laboratory monitoring in intensive care. In various circumstances PCT demonstrates more differentiating properties than other acute phase reactants including CRP. It contributes to monitoring of the severity of the patient’s state.

        Key words: procalcitonin, C-reactive protein, acute phase reactants, systemic inflammatory response syndrome, sepsis.