title: Giant cell arteritis: laboratory predictors of a positive temporal artery biopsy.
abstract: OBJECTIVE
  To identify laboratory predictors of a positive temporal artery biopsy.
  
  
  METHODS
  Cross-sectional study using retrospective electronic data base review.
  
  
  METHODS
  There were 3001 patients who had a temporal artery biopsy.
  
  
  METHODS
  The electronic database of a large health maintenance organization was searched for all patients who had a temporal artery biopsy performed from 1997 to 2006.
  
  
  METHODS
  Odds ratios for erythrocyte sedimentation rate, C-reactive protein (CRP), and platelet count values associated with a positive temporal artery biopsy.
  
  
  RESULTS
  Four hundred fifty-nine cases of biopsy-proven giant cell arteritis were identified. The odds of a positive biopsy were 1.5 times greater with an erythrocyte sedimentation rate of 47 to 107 mm/hr, 5.3 times greater with a CRP >2.45 mg/dL, and 4.2 times greater with platelets >400,000/μL.
  
  
  CONCLUSIONS
  In this largest population-based giant cell arteritis study in the United States to date, we reaffirm Hayreh's finding of the significance of a CRP level >2.45 mg/dL in predicting a positive biopsy. Our findings support the literature suggesting that CRP and thrombocytosis may be stronger predictors of positive biopsy than erythrocyte sedimentation rate.
  
  
  BACKGROUND
  The authors have no proprietary or commercial interest in any of the materials discussed in this article.
authors.affiliation: PGY-2 Internal Medicine, University of California San Francisco-Fresno, Fresno, California 93701, USA. mwalvick@gmail.com
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Walvick
authors.forename: Michael P
authors.initials: MP
authors.lastname: Walvick
mesh_terms: D000368:Aged; D001706:Biopsy; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000378:metabolism; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005260:Female; D013700:Giant Cell Arteritis / Q000453:epidemiology / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D015994:Incidence; D008297:Male; D016017:Odds Ratio; D015995:Prevalence; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013699:Temporal Arteries / Q000473:pathology*; D014481:United States / Q000453:epidemiology
chemical_list: D002097:C-Reactive Protein