title: Usefulness of procalcitonin for differentiation between activity of systemic autoimmune disease (systemic lupus erythematosus/systemic antineutrophil cytoplasmic antibody-associated vasculitis) and invasive bacterial infection.
abstract: OBJECTIVE
  To investigate whether the determination of serum procalcitonin (PCT) in systemic autoimmune disease will help to discriminate invasive infection from highly active underlying disease.
  
  
  METHODS
  Three hundred ninety-seven serum samples, from 18 patients with systemic lupus erythematosus (SLE) and 35 patients with systemic antineutrophil cytoplasmic antibody-associated vasculitis (AAV), were analyzed. Clinical disease activity was assessed by the Systemic Lupus Activity Measure in SLE patients and by the Birmingham Vasculitis Activity Score in AAV patients. Procalcitonin concentrations were determined in parallel with concentrations of neopterin, interleukin-6 (IL-6), and C-reactive protein (CRP). Additionally, serum creatinine values were obtained.
  
  
  RESULTS
  In 321 of the 324 samples from the 42 patients with autoimmune disease but without systemic infection, serum PCT levels were within the normal range (i.e., <0.5 ng/ml), whereas the values for neopterin, IL-6, and CRP were elevated in patients with active underlying disease. All 16 systemic infections occurred in 11 patients with AAV, and were associated with PCT levels that were markedly elevated, to a mean +/- SD of 1.93 +/- 1.19 ng/ml. No correlation between the degree of renal impairment and PCT concentrations was seen.
  
  
  CONCLUSIONS
  PCT may serve as a useful marker for the detection of systemic bacterial infection in patients with systemic autoimmune disease.
authors.affiliation: Medizinische Hochschule Hannover, Germany.
authors.forename: O K
authors.initials: OK
authors.lastname: Eberhard
authors.forename: M
authors.initials: M
authors.lastname: Haubitz
authors.forename: F M
authors.initials: FM
authors.lastname: Brunkhorst
authors.forename: V
authors.initials: V
authors.lastname: Kliem
authors.forename: K M
authors.initials: KM
authors.lastname: Koch
authors.forename: R
authors.initials: R
authors.lastname: Brunkhorst
mesh_terms: D019268:Antibodies, Antineutrophil Cytoplasmic / Q000032:analysis*; D001327:Autoimmune Diseases / Q000175:diagnosis*; D001424:Bacterial Infections / Q000175:diagnosis*; D015415:Biomarkers / Q000097:blood*; D001708:Biopterins / Q000031:analogs & derivatives / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D003404:Creatinine / Q000097:blood; D003937:Diagnosis, Differential; D006023:Glycoproteins / Q000097:blood*; D014890:Granulomatosis with Polyangiitis / Q000175:diagnosis*; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D008180:Lupus Erythematosus, Systemic / Q000175:diagnosis*; D019798:Neopterin; D011498:Protein Precursors / Q000097:blood*; D014657:Vasculitis / Q000175:diagnosis*
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers; C000606589:CALCA protein, human; D006023:Glycoproteins; D015850:Interleukin-6; D011498:Protein Precursors; D001708:Biopterins; D019798:Neopterin; D002116:Calcitonin; D002097:C-Reactive Protein; D003404:Creatinine; D015740:Calcitonin Gene-Related Peptide