Effects of the Storage Solution Type and Prolonged Storage on the Immunoreactivity of Cells

Our plain-English summary of Effects of the Storage Solution Type and Prolonged Storage on the Immunoreactivity of Cells, by K. Ikeda, S. Sato, H. Chigira, et al (Acta Cytologica, 2020).

The study

• Authors: K. Ikeda, S. Sato, H. Chigira, Y. Shibuki, N. Hiraoka
• Journal: Acta Cytologica
• Published: 2020;64(4):352-359
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: In effusion cytology, immunocytochemistry is a useful staining approach to provide important information for diagnosis. Effusion cytology is performed not only for pleural effusions and ascites but also for peritoneal and needle washing from fine needle aspirations or instruments. Although various solutions are used for washing cytology, the effect of the solution type on immunocytochemical reactivity is not fully understood. In this study, we examined the immunocytochemical reactivity of cytological samples after storage in various solutions.

Methods: Cell block specimens were obtained from ascites of patients with peritoneal cancer and pleural effusions of patients with diffuse malignant mesothelioma. Various solutions, including physiological saline (PS), Ringer solution, a low-molecular-weight dextran L injection, Voluven 6% solution, Mixid L injection, RPMI-1640 medium, and horse serum were added to the sediment layers of aliquots. All samples were kept at 4°C, and aliquots were subsequently processed at specific time points (0, 1, 2, 4, 7, and 14 days). Formalin-fixed, paraffin-embedded, cell block samples were prepared for immunocytochemical staining. Immunocytochemical results were analyzed for differences in the percentages of positive cells, using the effusion sample stored for 1 h as standard (100%).

Results: For all solutions other than PS, the median and central 50% of values were <100% (with respect to the effusion sample as a standard) after 1 h of storage. Immunoreactivity decreased for most solutions as time progressed.

Conclusion: Of note, immunocytochemistry results obtained using a washing solution are different from those using an effusion sample. For cytology, when a washing solution was used or when a sample was stored for a long time, the accuracy of the immunocytochemical results was low.

© 2019 S. Karger AG, Basel.

In plain English

This was a laboratory study of how the liquid a cell sample is stored in, and how long it is stored, affects immunocytochemical staining, a test used to identify cancer cells in body fluids. It did not study asbestos exposure. The authors used fluid from two patients: ascites (abdominal fluid) from one patient with peritoneal cancer, and pleural effusion from one patient with diffuse malignant mesothelioma. Portions were kept at 4 degrees C either as plain fluid or in one of seven solutions, including physiological saline, RPMI-1640 and horse serum. They were processed at times from 1 hour to 14 days. Results were compared with the plain fluid sample stored for 1 hour. After 1 hour, the median and middle half of values were below 100% for every solution except saline. The markers D2-40 and calretinin, used on the mesothelioma sample, had medians of 53.7% and 46.1%. Staining declined over time for nearly all solutions, and least for RPMI-1640. The authors concluded that staining results were unreliable when a washing solution was used or a sample was stored for a long time. They noted that only two patient samples were studied.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory experiment on stored cytology (body-fluid cell) samples
• Who was studied: Fluid samples from 2 patients: ascites from one patient with peritoneal cancer and pleural effusion from one patient with diffuse malignant mesothelioma. Ethics approval came from the National Cancer Center Hospital, Japan, and the International University of Health and Welfare. No dates are given.
• Exposure: Not an asbestos exposure. The samples were stored at 4 degrees C either as untreated effusion or in one of seven solutions: physiological saline, Ringer solution, low-molecular-weight dextran L injection, Voluven 6% solution, Mixid L injection, RPMI-1640 and horse serum. They were fixed in formalin after 1 hour, 24 hours, and 2, 4, 7 and 14 days.
• Main results:
  • After 1 hour of storage, the median and central 50% of values were below 100% of the effusion standard for all solutions except physiological saline.
  • After 1 hour, the central 50% of values ranged from 41.0% to 98.2% for samples in Voluven 6% solution, and from 93.2% to 109.4% for samples in physiological saline.
  • After 1 hour, the median values across solutions were 53.7% for D2-40 and 46.1% for calretinin. These two markers were used on the mesothelioma sample.
  • Comparing 1 hour with 14 days of storage, 8 of 9 antibodies showed significant differences in dextran L, Voluven, Mixid L and horse serum. Seven did in the untreated effusion, saline and Ringer solution, and 3 did in RPMI-1640.
  • PAX8 and calretinin were the markers most affected by prolonged storage, and CK5/6 was the least affected.
  • After 1 hour of storage, nuclear antigens showed minimal decline (93.8%), while cell membrane antigens showed a significant decrease (68.1%). Both declined over time.
  • In RPMI-1640, the effect of prolonged storage was minimal, but staining fell during 1 hour of storage (median 82.9%).
• The authors' conclusion: The authors concluded that when a washing solution was used, or a sample was stored for a long time, the immunocytochemical profile was unreliable.
• Limitations the authors state:
  • Only two patient samples were studied.
  • The differences between solutions in the 1-hour comparison were not statistically significant because few solutions were examined.
  • Staining intensity was not examined, and the amount of antigen cannot be quantified by immunostaining.

Topics

Medical terms in this study, explained in our Lexicon: Cytology, Pleural Effusion, Ascites, Cell Block, Malignant Mesothelioma.

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