Introduction: The aim of this retrospective study was to evaluate the preservation of biomarkers immunoreactivity on cytospins protected with polyethylene glycol (PEG).
Methods: In two independent cytopathology laboratories, immunocytochemical reactions were retrospectively evaluated on methanol-fixed and PEG-protected cytospins stored at room temperature (RT) for different time periods and compared with immunocytochemical reactions on corresponding baseline methanol-fixed cytospins. Semi-quantitatively assessed immunoreactivity, using scores from 0 to 3, was considered reduced if two sequential scores were lowered by at least one point.
Results: Immunocytochemical reactions for 40 biomarkers with membrane (10), cytoplasmic (22) and nuclear (8) localisation were performed on 921 slides prepared from 183 cytological samples. For the majority of biomarkers (29/37, 78%), immunoreactivity on PEG-protected cytospins stored at RT remained unchanged in the first 12 months. Immunoreactivity for GFAP, p40 and hepatocyte antigen was monitored and remained unchanged for 1, 8 and 7 months, respectively. Partial or complete loss of immunoreactivity on PEG-protected cytospins stored for less than 12 months was found on a single sample out of the total evaluated for CD3 (1/7), CD30 (1/4), CD45 (1/10), CK5/6 (1/7), MelanA (1/7) and vimentin (1/7), while more frequent changes of immunoreactivity were found for Ki67 (4/7) and p63 (2/7).
Conclusion: Immunoreactivity on cytospins protected with PEG and stored at RT is well-preserved for at least 12 months for the majority of biomarkers.
Keywords: biomarkers; immunocytochemistry; immunoreactivity; polyethylene glycol; preservation.
© 2020 John Wiley & Sons Ltd.