Prospective study comparing scrape cytology with frozen section in the intraoperative identification of parathyroid tissue.

Objective: Intraoperative identification of parathyroid tissue is crucial during parathyroid surgery. Frozen section is the most common tool, but is time-consuming and expensive. Scrape cytology is a modification of imprint cytology that provides rapid and cheap intraoperative identification of parathyroid tissue, but its reliability remains controversial. We assessed the sensitivity and specificity of scrape cytology in the intraoperative identification of parathyroid tissue.

Methods: Scrape cytology samples from parathyroid tissue (n=29), adipose tissue (n=3) and thyroid tissue (n=2) were prepared intraoperatively using May-Grünwald-Giemsa and Papanicolaou staining and subsequently sent for routine frozen section and standard paraffin section. A single pathologist reading the scrape cytology was blinded to the results of the frozen and standard paraffin sections.

Results: Scrape cytology identified 25 of 29 parathyroid tissues, all three adipose tissues and one of two thyroid tissues. The remaining samples, four parathyroid tissues and one thyroid tissue, were not identified due to insufficient sample for diagnosis. The result translated to give a diagnostic accuracy of 88.2%, sensitivity of 86%, and specificity of 100%. All tissues were accurately identified by frozen section.

Conclusion: Scrape cytology is a rapid, economical test with acceptable sensitivity and high specificity. It can be used as an adjunct to frozen section and may be used as a tool in helping surgeons to identify parathyroid tissue.