title: Periarticular osteoporosis: a useful feature in the diagnosis of early rheumatoid arthritis? Reliability and validity in a cross-sectional diagnostic study using dual-energy X-ray absorptiometry.
abstract: OBJECTIVE
  To identify regions of interest (ROIs) relevant to periarticular osteoporosis in RA with low precision error and sufficient inter-rater reliability and to test diagnostic validity for RA.
  
  
  METHODS
  Periarticular BMD was measured using dual-energy X-ray absorptiometry (DXA). Five ROIs were defined around MCP and/or PIP joints II-V, II-IV and mid-metacarpal to mid-phalangeal. They were evaluated for precision using the root mean square coefficient of variation (RMS-CV) and the intra-class correlation coefficient (ICC) for inter-reader reliability. To test validity, established RA patients (n = 25) and early arthritis patients (n = 25) were compared with healthy controls (n  = 37) matched on sex, age and menopausal status using paired t-tests, ROC curves and scatterplots.
  
  
  RESULTS
  The RMS-CV was 0.45-1.07%. The ICC was 0.99. Mean BMDs of the five ROIs ranged from 0.321 to 0.372 g/cm(2) in established RA, from 0.321 to 0.382 g/cm(2) in early arthritis and from 0.342 to 0.401 g/cm(2) in healthy controls. Mean differences ranged from 0.012 to 0.032 g/cm(2) for established RA and from 0.023 to 0.033 g/cm(2) for early arthritis patients compared with matched controls, with P < 0.05 for ROIs 1-5 in early arthritis and the whole hand in established RA. ROC curves indicated low discriminative power, with an area under the curve (AUC) of 0.61-0.64, and scatterplots showed great overlap between BMD values of patients and controls.
  
  
  CONCLUSIONS
  Periarticular BMD measured with DXA seems not to be a useful diagnostic feature due to strong overlap of BMD values between healthy controls, established RA patients and early arthritis patients.
authors: Department of Rheumatology, Erasmus MC, University Medical Center Rotterdam, CA Rotterdam, The Netherlands. c.alves@erasmusmc.nl
authors: Celina
authors: C
authors: Alves
authors: Edgar M
authors: EM
authors: Colin
authors: Wouter J
authors: WJ
authors: van Oort
authors: Johanna P
authors: JP
authors: Sluimer
authors: Johanna M W
authors: JM
authors: Hazes
authors: Jolanda J
authors: JJ
authors: Luime
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015519:Bone Density / Q000502:physiology; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D042241:Early Diagnosis; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010024:Osteoporosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011446:Prospective Studies