Virtual microscopy as a tool for proficiency testing in cytopathology: a model using multiple digital images of Papanicolaou tests

Abstract

Background: Modern digital cameras can acquire images from cytologic slides at sufficient resolution to allow for digital enlargement and scrolling on a video monitor, allowing for the simulation of microscopy using a computer.

Objective: The purpose of this study was to develop a tool for proficiency testing in cytopathology using multiple digital images of Papanicolaou tests.

Methods: Nine images were photographed from each of 10 Papanicolaou tests at x100 optical magnification, 3400 x 2300-pixel resolution, using a light microscope and a digital camera. All images from each case were tiled in a single canvas with Photoshop 4.0 software. Two cytopathologists and 3 cytotechnologists interpreted these "virtual slides" using a computer and graded diagnostic codes (PAP program, College of American Pathologists). Subjects were retested a year later using the glass slides from the same cases and routine microscopy. Both test results, by diagnostic code, were compared with the McNemar test of symmetry.

Results: The 5 test subjects provided 42 and 50 correct diagnostic codes by "virtual microscopy" and light microscopy, respectively. No significant asymmetry in results obtained by virtual microscopy and light microscopy was encountered with the McNemar test of symmetry. All test answers were correctly classified by selection series, using both virtual microscopy and light microscopy, and the responses would have been graded as 100% by current PAP program scoring guidelines. This suggests that virtual microscopy could be used for proficiency testing purposes.

Conclusions: A simple virtual microscopy method designed to challenge participants to locate and diagnose cells of interest was effective for the administration of standardized proficiency tests. Virtual microscopy methods that rely on single-plane images to locate and diagnose cells of interest could provide effective proficiency testing tools prior to the development of more computationally intensive systems that represent an entire Papanicolaou test at multiple focal planes.