title: Procalcitonin for discrimination between activity of systemic autoimmune disease and systemic bacterial infection.
abstract: OBJECTIVE
  To investigate whether serum procalcitonin (PCT) levels could be useful to differentiate between systemic infection and the activity of the underlying disease in autoimmune disease.
  
  
  METHODS
  In 18 patients with systemic lupus erythematodes (SLE) and 35 patients with systemic antineutrophil cytoplasmic antibody-associated vasculitis (AAV) clinical disease activity was assessed by score systems. Infection was defined by clinical and microbiological means. PCT was determined in parallel with concentrations of neopterin, interleukin-6 (IL-6), and C-reactive protein (CRP) in 397 serum samples.
  
  
  RESULTS
  Only in 3 of the 324 samples taken from patients with autoimmune disease but without concomitant infection, serum PCT levels were above the normal range (>0.5 ng/ml), whereas neopterin, CRP and IL-6 were elevated in patients with active underlying disease. All systemic infections (N=16 in AAV-patients) were associated with markedly elevated PCT-levels (mean+/-SD:1.93+/-1.19 ng/ml).
  
  
  CONCLUSIONS
  PCT may serve as a useful marker for the detection of systemic bacterial infection in patients with autoimmune disease.
authors.affiliation: Medizinische Hochschule Hannover, Abt. Nephrologie, Carl-Neubert-Str.1, D-30623 Hannover, Germany. brunkhorst@tx.amb-hannover.de
authors.forename: R
authors.initials: R
authors.lastname: Brunkhorst
authors.forename: O K
authors.initials: OK
authors.lastname: Eberhardt
authors.forename: M
authors.initials: M
authors.lastname: Haubitz
authors.forename: F M
authors.initials: FM
authors.lastname: Brunkhorst
mesh_terms: D000328:Adult; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D001424:Bacterial Infections / Q000097:blood / Q000175:diagnosis*; D015415:Biomarkers / Q000097:blood; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011498:Protein Precursors / Q000097:blood*; D012680:Sensitivity and Specificity; D014657:Vasculitis / Q000097:blood / Q000175:diagnosis*
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers; C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide