title: Serum procalcitonin and C-reactive protein for differentiating bacterial infection from disease activity in patients with systemic lupus erythematosus.
abstract: OBJECTIVE
  To study the clinical value of procalcitonin (PCT) and C-reactive protein (CRP) in differentiating bacterial infection from disease activity in systemic lupus erythematosus (SLE) patients.
  
  
  METHODS
  PCT and CRP in active SLE patients complicated with and without bacterial infection were retrospectively studied. Bacterial infection was diagnosed by positive culture results or typical symptoms and signs combined with positive response to antibiotics. Disease activity of SLE was assessed by systemic lupus erythematosus disease activity index (SLEDAI).
  
  
  RESULTS
  One hundred and fourteen active SLE patients were recruited, 47 of which were with bacterial infection and 67 were non-infected. PCT and CRP levels were significantly elevated in patients with bacterial infection (P < 0.05). The ideal cutoff value for PCT was 0.38 ng/ml, at which the sensitivity (74.5%) and specificity (95.5%) combined the best. The negative predictive value and positive predictive value to detect bacterial infection were 84.2% and 92.1%, respectively. PCT but not the CRP level in the septic patients was significantly higher than that of non-septic ones. Meanwhile, in patients with SLEDAI score of > 10, both PCT and CRP levels were higher in patients with bacterial infection, but the difference was only statistically significant for PCT (P < 0.05). PCT was significantly reduced after anti-bacterial treatment.
  
  
  CONCLUSIONS
  PCT test is superior to CRP test in detecting superimposed bacterial infection in active SLE patients. The levels of PCT are correlated with the severity of bacterial infection and can be used to monitor the response to antibiotic treatment.
authors.affiliation: Department of Rheumatology, The First Affiliated Hospital of Sun Yat-sen University , Guangzhou , P. R. China.
authors.forename: Jinquan
authors.initials: J
authors.lastname: Yu
authors.forename: Bingling
authors.initials: B
authors.lastname: Xu
authors.forename: Yuefang
authors.initials: Y
authors.lastname: Huang
authors.forename: Jijun
authors.initials: J
authors.lastname: Zhao
authors.forename: Shuang
authors.initials: S
authors.lastname: Wang
authors.forename: Hongyue
authors.initials: H
authors.lastname: Wang
authors.forename: Niansheng
authors.initials: N
authors.lastname: Yang
mesh_terms: D000293:Adolescent; D000328:Adult; D001424:Bacterial Infections / Q000097:blood / Q000175:diagnosis*; D002097:C-Reactive Protein / Q000378:metabolism*; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011498:Protein Precursors / Q000097:blood*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D002097:C-Reactive Protein; D015740:Calcitonin Gene-Related Peptide