title: Cytidine deaminase may be a useful marker in differentiating elderly onset rheumatoid arthritis from polymyalgia rheumatica/giant cell arteritis.
abstract: OBJECTIVE
  PMR/GCA is a relatively common inflammatory disease in the elderly population. Clinical differentiation from a polymyalgic onset of RA in the elderly can be difficult. We have examined in a preliminary study the hypothesis that serum cytidine deaminase (CD) may be valuable in the differential diagnosis of these disorders.
  
  
  METHODS
  CD was assayed by a spectrophotometric method in 20 patients with active PMR/GCA, both before and after treatment with prednisolone, and was compared with serum CD levels in 20 patients with active RA.
  
  
  RESULTS
  CD levels were within the normal range (< 10 units/ml) in 36 of the 40 samples from patients with PMR/GCA: The mean CD in pre-treatment samples was 8.64 units/ml (SD 7.09), and after treatment 7.20 units/ml (SD 3.53). The mean serum CD in the RA patients was 21.33 units/ml (SD 8.94), significantly higher than in PMR/GCA (p < 0.0001).
  
  
  CONCLUSIONS
  Serum CD levels were significantly different when proven PMR was compared with established, long-standing RA. Therefore, serum CD could be a useful diagnostic marker for differentiating PMR/GCA from active RA in older patients.
authors.affiliation: Rheumatology Unit, Bristol Royal Infirmary, University of Bristol, UK.
authors.forename: D
authors.initials: D
authors.lastname: Kassimos
authors.forename: J R
authors.initials: JR
authors.lastname: Kirwan
authors.forename: V
authors.initials: V
authors.lastname: Kyle
authors.forename: B
authors.initials: B
authors.lastname: Hazleman
authors.forename: P
authors.initials: P
authors.lastname: Dieppe
mesh_terms: D017668:Age of Onset; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000201:enzymology; D004796:Clinical Enzyme Tests; D003564:Cytidine Deaminase / Q000097:blood*; D003937:Diagnosis, Differential; D005260:Female; D013700:Giant Cell Arteritis / Q000175:diagnosis* / Q000201:enzymology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011111:Polymyalgia Rheumatica / Q000175:diagnosis* / Q000201:enzymology; D013053:Spectrophotometry
chemical_list: D003564:Cytidine Deaminase