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Standardization of conjunctival impression cytology
A J Martinez1, M B Mills, K B Jaceldo
1Center for Sight, Georgetown University Hospital, USA.
Abstract:
Lack of standardization limits the potential of conjunctival impression cytology as a clinical and research tool. This may be attributed to the variety of filter paper currently used. MF Millipore membrane filters of pore sizes 8.0, 3.0, 0.45, 0.22, and 0.025 micron were tested. Samples obtained from 30 eyes of rabbits were randomized and scored by four masked observers for cellularity and morphologic preservation. Cellularity was significantly greater with pore sizes 8.0, 3.0, and 0.45 micron versus 0.22 and 0.025 micron (p < or = 0.001), with an 83% correlation among four scorers. In contrast, morphology was better preserved in the smaller pore size papers (0.22 and 0.025 micron) when compared with larger pore sizes (p = 0.048). Using the best two filter papers (0.22 and 0.025 micron) and an ophthalmodynamometer, either 40, 60, or 80 g of pressure was applied for 3 s to each pore size paper to see whether cellularity could be increased. Cellularity was greater with pore size 0.22 than 0.025 micron (42.3 +/- 19.8 versus 8.7 +/- 6.4). Regardless of the pore size of the filter paper, cellularity was significantly improved at 60 g when compared with either 80 or 40 g. The results show that to maximize cell acquisition, a paper with medium pore size (0.22 micron) and a pressure of 60 g may be the best choice.
Insights
Standardizing conjunctival impression cytology requires optimal filter paper. A 0.22-micron pore size filter with 60g pressure maximizes cell acquisition for this clinical tool.
Area of Science:
- Ophthalmology
- Cell Biology
- Biomaterials Science
Background:
- Conjunctival impression cytology is a valuable clinical and research tool.
- Lack of standardization, particularly in filter paper selection, hinders its potential.
- Variability in filter paper types affects sample quality and reproducibility.
Purpose of the Study:
- To evaluate the impact of different filter paper pore sizes on conjunctival impression cytology.
- To determine optimal pressure application for maximizing cell yield.
- To identify the best filter paper and pressure combination for improved standardization.
Main Methods:
- MF Millipore membrane filters with pore sizes ranging from 0.025 to 8.0 microns were tested.
- Samples from rabbit eyes were scored by masked observers for cellularity and morphology.
- An ophthalmodynamometer was used to apply pressures of 40, 60, and 80g to filter papers.
Main Results:
- Higher cellularity was observed with larger pore sizes (8.0, 3.0, 0.45 micron) compared to smaller ones (0.22, 0.025 micron).
- Better morphologic preservation was achieved with smaller pore size filters (0.22 and 0.025 micron).
- A pressure of 60g significantly improved cellularity compared to 40g or 80g, especially with the 0.22-micron filter.
Conclusions:
- A filter paper with a medium pore size (0.22 micron) offers a balance between cellularity and morphology.
- Applying 60g of pressure is optimal for maximizing cell acquisition in conjunctival impression cytology.
- These findings provide a basis for standardizing filter paper selection and pressure application.