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Biopsy of the temporal artery can be used to confirm giant cell arteritis (GCA) well after corticosteroid treatment has started, according to a small prospective study. The findings will need to be verified by a larger study, but it now seems that treatment need not be delayed for a biopsy for fear of compromising the histological picture. Usually, a biopsy is performed within two weeks of starting treatment.
Temporal artery biopsy specimens from nine of the 11 patients in the study showed features of GCA—that is, giant cells in the intima and media, lymphocytes and histiocytes in the media, reduplication or fragmentation of the internal elastic lamina, and thickening of the intima. In two of the nine the appearance indicated healed GCA. Three of four specimens (75%) were positive within two weeks after starting corticosteroid treatment and six of seven (86%) after 4–6 weeks.
The patients received a standardised regimen of high dose corticosteroids according to whether they had visual loss on referral or not. At entry to the study they were randomised to receive biopsy before treatment; within in week after treatment started; at 2–3 weeks; and at 4–6 weeks. Patients were receiving at least 40 mg prednisolone when undergoing biopsy. Each paraffin block of biopsy material was cut at 4–5 μm thickness in at least three levels for staining and histological examination.
Previously there has been controversy about whether corticosteroid treatment obscures the pathological features of biopsy material, but this has been based on retrospective studies.