The influence of sectional interval on the reliability of temporal arterial biopsies in polymyalgia rheumatica.

Temporal arterial biopsies from 27 patients with a clinical diagnosis of pure polymyalgia rheumatica (PMR) were examined using light microscopy on paraffin and plastic sections. The primary routine examination of the paraffin-embedded parts of the biopsies (biopsy length: 12.7 +/- 4.5 mm, sub-segments: 4.9 +/- 1.2 mm) revealed 4 positive cases, whereas the primary examination of the smaller plastic-embedded parts showed inflammation in 6 cases (biopsy length: 2.7 +/- 1.2 mm, sub-segments: 0.7 +/- 0.3 mm). Serial sectioning with a 50 microns interval of arteries which were negative primarily revealed three new positive cases in the paraffin-embedded material (total length: 174.0 mm), whereas sectioning the plastic-embedded material (total length: 52.8 mm) produced one more positive artery. All the new cases displayed a focal inflammatory process in atrophic, calcified arterial segments. The high yield of positive biopsies in the present material (11 of 27; 40.7%) demonstrates the diagnostic value of temporal arterial biopsy in PMR and the importance of a careful histologic examination. The results also indicate the influence of biopsy length on the yield of positive biopsies. The division of fixed temporal arterial biopsies into approximately 1-mm-long sub-segments before the embedding and the further serial sectioning of those negative biopsies which are atrophic and/or calcified is recommended in cases of pure PMR.