699 Accounting for Fixation Shrinkage in Temporal Artery Biopsy

Abstract

Abstract Aim Ascertain the length shrinkage of Temporal Artery Biopsy (TAB) following fixation to inform current practice and ensure samples taken are in keeping with the British Society of Rheumatology Recommendations. The British Society of Rheumatology (2020) recommends a sample size of at least 1cm post fixation to be of diagnostic value for Giant Cell Arteritis (GCA). Formalin has been shown to cause 20–30% volume shrinkage of histopathological specimens. Shrinkage relating to length, specifically with TABs was shown to be approximately 8% based on a sample size of 13 patients. Method A consecutive sample of patients undergoing TAB between January-December 2021 were analysed. Those with measurements documented in the op note were compared to the post fixation measurement documented in the histopathology report. Statistical analysis included demographic data as well p values calculated for the differences in length. Results Forty Seven patients were treated for TAB, M:F (1:1.26), Mean Age=73.06 (47–94). Mean pre-fixation length = 26.84mm (SD-8.38), Mean post-fixation length = 20.27mm (SD-8.72). Overall shrinkage was calculated at 25% with a p value of 0.0046, confirming a significant difference between the two sample groups. Conclusion This sample demonstrates there to be a clear difference between the two measurements, with a significant percentage shrinkage. Appreciation of shrinkage is vital in obtaining a suitable sample to ensure diagnostic value and appropriate patient care. Further evaluation, both prospective and retrospective is underway with the results pending.