Department of Technology, Faculty of Health and Technology, University College Copenhagen, Copenhagen, Denmark
Lisbon School of Health Technology, Polytechnic Institute of Lisbon, Lisbon, Portugal.
J Clin Pathol. 2021 Mar;74(3):149-156. doi: 10.1136/jclinpath-2020-206612. Epub 2020 Jul 15.
Though formalin remains to be the gold standard fixative in pathology departments, analytical challenges persist for nucleic acid evaluations. In our laboratory, formalin fixation of skin samples in particular impairs diagnostic accuracy and demands repetition of biopsies and analytical procedures. PAXgene Tissue Systems may be an alternative; however, according to manufacturer specifications it only allows fixation for 48 hours before having to add a stabiliser. This may be a challenge in laboratories, which are closed in weekends and bank holidays. Our aim was to validate this alternative fixative for dermatological samples with prolonged fixation times using standard laboratory protocols developed for formalin-fixed specimens. We compared the results with gold standard formalin fixation.
Skin specimens were formalin or PAXgene fixed for either 2 hours, 24 hours, 3 days or 7 days, paraffin-embedded, analysed and scored by observers.
Generally, formalin outperformed PAXgene fixation in H&E stains and fluorescence in situ hybridisation (FISH), but both seem usable for diagnostics. Time of PAXgene fixation did not have an impact on alcian blue-Van Gieson (ABVG), H&E (p=0.48), nor immunohistochemistry (p=0.74). There was a tendency towards best PAXgene performance at 24 hours of fixation for FISH, and for DNA integrity analysis 24 hours or 3 days.
Prolonging PAXgene fixation time to 3 days before adding stabiliser does not seem to have major impact on performance of general diagnostic analysis, but our preliminary results show optimisation of internal protocols are needed. PAXgene is an expensive alternative and may be confined to some dermatological samples.
尽管福尔马林仍然是病理科的金标准固定剂，但核酸评估仍存在分析挑战。在我们的实验室中，福尔马林固定皮肤样本特别会影响诊断准确性，并需要重复活检和分析程序。PAXgene Tissue Systems 可能是一种替代方法；然而，根据制造商的规格，它只能在固定 48 小时之前添加稳定剂。这在周末和银行假日关闭的实验室可能是一个挑战。我们的目的是使用为福尔马林固定标本开发的标准实验室方案来验证这种替代固定剂在延长固定时间的皮肤科样本中的有效性。我们将结果与金标准福尔马林固定进行了比较。
皮肤标本分别用福尔马林或 PAXgene 固定 2 小时、24 小时、3 天或 7 天，石蜡包埋，由观察者进行分析和评分。
一般来说，福尔马林在 H&E 染色和荧光原位杂交（FISH）中优于 PAXgene 固定，但两者似乎都可用于诊断。PAXgene 固定时间对阿尔辛蓝-Van Gieson（ABVG）、H&E（p=0.48）和免疫组织化学（p=0.74）均无影响。在 FISH 中，24 小时固定时 PAXgene 的性能最佳，而在 DNA 完整性分析中，24 小时或 3 天固定时 PAXgene 的性能最佳。
在添加稳定剂之前将 PAXgene 固定时间延长至 3 天似乎不会对一般诊断分析的性能产生重大影响，但我们的初步结果表明需要优化内部方案。PAXgene 是一种昂贵的替代品，可能仅限于某些皮肤科样本。
