title: The usefulness of neutrophil CD64 expression in the diagnosis of local infection in patients with rheumatoid arthritis in daily practice.
abstract: BACKGROUND
  The diagnosis of local infection in patients with rheumatoid arthritis (RA) is frequently difficult because clinical signs and symptoms and laboratory test results of local infection are also observed in arthritis of active RA. The need for a specific marker of infection is high in RA patients. The usefulness of neutrophil CD64 expression (CD64) to diagnose local musculoskeletal infection (local infection) and discriminate local infection from RA-related inflammation in RA patients was examined.
  
  
  METHODS
  CD64 was measured by a quantitative method using flow cytometry in 61 RA patients in whom local infection was suspected, and the usefulness of CD64 was examined by comparing the findings with clinical results.
  
  
  RESULTS
  There were 25 patients with local infection and 36 patients without infection. The median CD64 value the patients with local infection was 3148 molecules/cell (interquartile range [IQR], 2140-6231) and that of the patients without infection was 1106 molecules/cell (IQR, 804-1464) with a statistically significant difference (P < 0.0001). In contrast, no significant difference between the groups was observed in C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell (WBC) count. The area under the curve of CD64 calculated by receiver operating characteristic curve analysis was larger than that of CRP, ESR, or WBC count, suggesting that CD64 has superior ability to discriminate of infection compared to these other markers. When the cutoff value of CD64 was set at 2000 molecules/cell, the sensitivity and specificity of CD64 for the detection of local infection in RA patients were 76.0% and 94.4%, respectively.
  
  
  CONCLUSIONS
  CD64 is a useful marker in RA patients to discriminate local infection from RA-related inflammation.
authors: Nishino Clinic Orthopedics and Rheumatology, 2-9-15 Nishigaoka, Kita-ku, Tokyo 115-0056, Japan.
authors: Jinju
authors: J
authors: Nishino
authors: Sakae
authors: S
authors: Tanaka
authors: Yuho
authors: Y
authors: Kadono
authors: Toshihiro
authors: T
authors: Matsui
authors: Akiko
authors: A
authors: Komiya
authors: Keita
authors: K
authors: Nishimura
authors: Shigeto
authors: S
authors: Tohma
mesh_terms: D000368:Aged; D001170:Arthritis, Infectious / Q000175:diagnosis* / Q000378:metabolism*; D001172:Arthritis, Rheumatoid / Q000150:complications*; D016022:Case-Control Studies; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000378:metabolism*; D012372:ROC Curve; D017452:Receptors, IgG / Q000378:metabolism*
chemical_list: D017452:Receptors, IgG