title: Cost-effectiveness of MR imaging in evaluating polymyositis.
abstract: OBJECTIVE
  Polymyositis is an inflammatory disorder of muscle that is often difficult to diagnose. The purpose of this study was to assess the usefulness and cost-effectiveness of MR imaging as a biopsy guide in patients with suspected polymyositis as an alternative to a blind biopsy.
  
  
  METHODS
  Our subjects were 25 patients with clinically suspected and ultimately confirmed polymyositis, 14 of whom had preoperative MR imaging at 1.5 T (including axial T1-weighted, axial T2-weighted [fat saturated], coronal T1-weighted, and coronal fast short-T1 inversion recovery images of both entire extremities). Images were prospectively interpreted for a specific location for a biopsy that showed the most muscle edema with the least atrophy. Surgical results and the estimated true cost of medical care (cost-accounting method) were compared between patients with preoperative MR images and patients whose biopsy site was selected on the basis of clinical criteria.
  
  
  RESULTS
  Among the 14 patients whose biopsy site was selected on the basis of MR findings, only one biopsy result was false-negative. Patients without imaging had five biopsies with false-negative results. Patients with preoperative MR images averaged actual medical costs of $14,000 compared with $20,000 for those without MR images. Hospitalization time averaged 12 days for patients with MR images for guidance compared with 14 days for those without MR images. The average daily cost was $1,150 for the patients with MR images compared with $1,390 for those without.
  
  
  CONCLUSIONS
  We conclude that MR imaging not only can aid in surgical planning but also can decrease the costs of patient care for patients with suspected polymyositis.
mesh_terms: D000328:Adult; D001706:Biopsy / Q000191:economics; D003362:Cost-Benefit Analysis; D005188:False Negative Reactions; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000191:economics* / Q000295:instrumentation / Q000379:methods; D008875:Middle Aged; D009132:Muscles / Q000473:pathology; D017285:Polymyositis / Q000175:diagnosis* / Q000191:economics; D011446:Prospective Studies