ObjectiveTo explore procalcitonin (PCT) dynamically in severe community-acquired pneumonia (SCAP) patients to evaluate the effects of different kinds of medical treatments and assess the clinical significance of the change of PCT. MethodsAll of the selected 60 SCAP patients treated from January 2009 to April 2011 met the standards of IDSA/ATS Guidelines for CAP. There were 38 males and 22 females, with an average age of 66.3 years. The sterile venous blood specimen samples were collected from the patients at day 0 to day 5. PCT and C-reactive protein (CRP) were measured by enzyme linked immunosorbent assay throughout the research. At day six, based on oxygenation index (PaO2/FiO2) ratio higher than 250, inflammation absorption on chest X ray after vasoactive agents were stopped, Glasgow scores higher than 10 and urine volume equal to or higher than 0.5 mL/(kg·d), we divided the patients into recovery group and deterioration group. Data were analyzed by SAS 9.0 software, and P<0.05 was considered to be statistically significant. ResultsThe analysis results showed that PCT and CRP bore a significantly positive relationship on day 0 (r=0.38, P=0.00). The research also indicated that PCT had a faster declining rate than CRP and white blood cells count throughout the clinical treatment. The average of PCT declined 29% in 48 hours. Following the criterion of PCT decrease by 30%, the research showed that PCT had a higher sensibility and specificity (66.87% and 85.50%, respectively) in 48 hours than 72 hours (70.05% and 100.00%), 96 hours (79.88% and 75.23%), and 120 hours (83.10% and 100.00%). ConclusionFollowing the criterion of PCT decrease by 30% after using antibiotics can be an clinical objective index to guide the use of antibiotics and provide the basis for clinical application and prognosis.