Giant cell arteritis: laboratory predictors of a positive temporal artery biopsy.

PURPOSE: To identify laboratory predictors of a positive temporal artery biopsy.

DESIGN: Cross-sectional study using retrospective electronic data base review.

PARTICIPANTS: 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.

MAIN OUTCOME MEASURES: 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.

FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any of the materials discussed in this article.