Initiation of glucocorticoid therapy: before or after temporal artery biopsy?

To identify clinical findings in patients with suspected giant cell arteritis (GCA) that may help clinicians decide when to initiate glucocorticoid therapy.

Medical diagnostic codes and surgical indexing were used to identify all patients who had temporal artery biopsy at the Mayo Clinic in Rochester, Minn, between January 1, 1988, and December 31, 1997. Patient medical records were abstracted for pertinent clinical data, glucocorticoid use, and final diagnoses. Sensitivities, specificities, predictive values, and likelihood ratios were calculated for the association of the various clinical findings and the presence of a positive biopsy result. Graphic and arithmetic models were constructed to predict positive temporal artery biopsy results.

During the 10-year interval, 1113 patients had temporal artery biopsy. The results were positive for GCA in 373 patients (33.5%) and negative in 740 (665%). Twenty percent of all patients were taking glucocorticoids at the time of biopsy. The presence of jaw claudication had a positive predictive value of 78. Combinations of jaw claudication with new headache, scalp tenderness, and decreased vision had still higher values. Positive likelihood ratios in patients with these combinations and in those with diplopia were greater than 3. A normal erythrocyte sedi-mentation rate in patients not taking corticosteroids provided a high negative likelihood ratio of 40. An arithmetic equation provided the probability of a positive biopsy result on a continuous scale using 6 variables identified by logistic regression. Patients with a greater than 80% chance of a positive biopsy result and those with less than a 10% chance were identified.

Positive predictive values, likelihood ratios, and an arithmetic formula identify patients who have an increased or decreased chance of a positive temporal artery biopsy result. Use of these methods to determine early initiation of glucocorticoid therapy before temporal artery biopsy or deferral until after biopsy may help reduce both vascular complications of GCA and adverse effects of corticosteroids.