Validation of a modified plasma-based cell block technique using activated partial thromboplastin time-ellagic acid reagent in body fluid and fine needle aspiration samples in cytology.

Abstract

Despite the availability of different cell block preparation techniques in the literature, there is an unmet need for a technique that meets the needs of a low-tech, low-resource laboratory for diagnostic and ancillary testing. We aimed to develop and validate a modified method of cell block preparation in terms of its efficacy in cellular preservation and its utility in ancillary testing. Cell blocks were prepared using fresh patient plasma and activated partial thromboplastin time-ellagic acid reagent. A prospective study was conducted to assess the performance of this modified plasma-based cell block in terms of (1) cell yield as well as morphologic and architectural preservation and (2) utility of the modified plasma-based cell block in immunohistochemistry in terms of preservation of antigenicity, staining quality, and the presence of background interference. Special stains and molecular testing were performed in select cases. Of the 64 samples we included, 59 met the inclusion criteria. Diagnostic concordance between cell block and smear was 92.6% in body fluids and 43.75% in fine needle aspiration cytologic aspirates. Among fluid sediment modified plasma-based cell blocks, 92.5% were representative, with minimal degeneration and excellent architecture, whereas fine needle aspiration cytologic modified plasma-based cell blocks showed representative material in 75.0%, minimal to moderate degeneration in 81.25%, and excellent architectural preservation in 58.3% of blocks. Immunohistochemistry performed in 9 cases showed strong staining in 90.0% and good clarity in 86.9% of cases, with no background staining. Special stains and selective molecular tests were successfully performed. Modified plasma-based cell block testing improves diagnostic yield and preserves morphology. Compatible with a broad spectrum of ancillary testing, chiefly immunohistochemistry and commonly used molecular tests, it is a feasible and cost-effective alternative.