title: Procalcitonin is a specific marker for detecting bacterial infection in patients with rheumatoid arthritis.
abstract: OBJECTIVE
  Rheumatoid arthritis (RA) is a chronic inflammatory disease accompanied by many complications, and serious infections are associated with many of the advanced therapeutics used to treat it. We assessed serum procalcitonin (PCT) levels to distinguish bacterial infection from other complications in patients with RA.
  
  
  METHODS
  One hundred eighteen patients experiencing an RA flare, noninfectious complication of RA or its treatment, nonbacterial infection, or bacterial infection were studied. Serum PCT concentrations were determined with a chemiluminescent enzyme immunoassay.
  
  
  RESULTS
  All patients experiencing an RA flare showed negative PCT levels (≤ 0.1 ng/ml; n = 18). The PCT level was higher in the bacterial infection group (25.8% had levels ≥ 0.5 ng/ml) than in the other 3 groups (0.0-4.3% had levels ≥ 0.5 ng/ml) and the difference was significant among groups (p = 0.003). Conversely, no statistically significant difference was observed among the groups with C-reactive protein (CRP) concentration ≥ 0.3 mg/dl (p = 0.513), white blood cell (WBC) count > 8500/mm(3) (p = 0.053), or erythrocyte sedimentation rate (ESR) > 15 mm/h (p = 0.328). The OR of high PCT level (≥ 0.5 ng/ml) for detection of bacterial infection was 19.13 (95% CI 2.44-149.78, p = 0.005). Specificity and positive likelihood ratio of PCT ≥ 0.5 ng/ml were highest (98.2% and 14.33, respectively) for detection of bacterial infection, although the sensitivity was low (25.8%).
  
  
  CONCLUSIONS
  Serum PCT level is a more specific marker for detection of bacterial infection than either CRP, ESR, or WBC count in patients with RA. High PCT levels (≥ 0.5 ng/ml) strongly suggest bacterial infection. However, PCT < 0.5 ng/ml, even if < 0.2 ng/ml, does not rule out bacterial infection and physicians should treat appropriately.
authors: Department of Rheumatology, Niigata Rheumatic Center, Shibata City, Niigata, Japan. hiroe-212@umin.ac.jp
authors: Hiroe
authors: H
authors: Sato
authors: Naohito
authors: N
authors: Tanabe
authors: Akira
authors: A
authors: Murasawa
authors: Yasuhiro
authors: Y
authors: Otaki
authors: Takehito
authors: T
authors: Sakai
authors: Toshiaki
authors: T
authors: Sugaya
authors: Satoshi
authors: S
authors: Ito
authors: Hiroshi
authors: H
authors: Otani
authors: Asami
authors: A
authors: Abe
authors: Hajime
authors: H
authors: Ishikawa
authors: Kiyoshi
authors: K
authors: Nakazono
authors: Takeshi
authors: T
authors: Kuroda
authors: Masaaki
authors: M
authors: Nakano
authors: Ichiei
authors: I
authors: Narita
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000150:complications*; D001424:Bacterial Infections / Q000097:blood / Q000150:complications / Q000175:diagnosis*; D015415:Biomarkers / Q000097:blood; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000378:metabolism; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D008297:Male; D008875:Middle Aged; D011498:Protein Precursors / Q000097:blood*; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D002097:C-Reactive Protein; D015740:Calcitonin Gene-Related Peptide