title: Introduction of a metabolic joint asymmetry score derived from conventional bone scintigraphy. A new tool to differentiate psoriatic from rheumatoid arthritis.
abstract: OBJECTIVE
  Clinical differentiation of psoriatic arthritis (PsA) and rheumatoid arthritis (rA) based on the pattern of joint involvement can be difficult; the frequent form of PsA with polyarthritis of the peripheral joints may sometime resemble rA. We investigated a metabolic joint asymmetry score (MJAS), reflecting the overall asymmetric joint involvement on conventional bone scintigraphy, for differentiating PsA from rA in patients presenting with peripheral polyarthritis.
  
  
  METHODS
  106 patients (n = 61, PsA; n = 45, rA) with peripheral polyarthritis (≥ 5 joints) as well as 26 control subjects with no history of chronic joint disorders were analyzed. The intensity of articular 99mTc-MDP uptake in 40 peripheral joint pairs was scored regarding the bilateral difference of each joint based on a scale of 0-2 (no significant, moderate, and marked asymmetry, respectively). The patient's MJAS was defined as the sum of uptake difference scores of all joint pairs. The association of MJAS with the underlying condition (Psoriasis criteria, Revised Criteria of the ACR) was examined.
  
  
  RESULTS
  5280 peripheral joint pairs were investigated. There was no significant difference in the total number of involved joints in PsA 15.0 ± 8.2 versus rA 17.5 ± 8.8 patients (p = 0.132), but significantly less involvement in the control group (6.7 ± 5.0, p < 0.001). MJAS was markedly higher in PsA (17.0 ± 9.6) than in rA (4.8 ± 3.9, p < 0.001), and correlated with the total number of involved joints in PsA (r = 0.516, p < 0.001), but not in rA (r = 0.078, p = 0.380). The MJAS disparity between PsA and rA persisted after exclusion of the DIP joints (14.4 ± 7.7 vs. 4.4 ± 3.3; p<0.001).
  
  
  CONCLUSIONS
  The new reproducible semi-quantification method for the asymmetry of metabolic joint involvement permits differentiation of psoriatic from rheumatoid peripheral arthritis with MJAS being markedly higher in patients with PsA as compared to rA patients. The score may offer an effective complementary tool for characterizing patients with peripheral polyarthritis.
authors: Samer Ezziddin, MD, PhD Department of Nuclear Medicine, Saarland University, Kirrberger Str. / Geb 50, 66421 Homburg, Germany, Tel. +49/(0)6841/162 - 22 01, Fax -46 92, E-mail: samer.ezziddin@uks.eu.
authors: S
authors: S
authors: Ezziddin
authors: F
authors: F
authors: Khalaf
authors: M
authors: M
authors: Seidel
authors: A
authors: A
authors: Al Zreiqat
authors: D
authors: D
authors: Wilsmann-Theis
authors: B
authors: B
authors: Simon
authors: H-J
authors: HJ
authors: Biersack
authors: A
authors: A
authors: Sabet
mesh_terms: D000328:Adult; D000368:Aged; D015535:Arthritis, Psoriatic / Q000000981:diagnostic imaging* / Q000378:metabolism*; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging* / Q000378:metabolism*; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000378:metabolism; D003198:Computer Simulation; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012984:Software; D013669:Technetium Tc 99m Medronate / Q000493:pharmacokinetics*
chemical_list: D019275:Radiopharmaceuticals; D013669:Technetium Tc 99m Medronate
keywords: Psoriatic arthritis; bone scintigraphy; rheumatoid arthritis