Impact of digital image manipulation in cytology

Digital images have become an important component of cytology practice. They are used in telecytology, automated screening, educational material, and Web sites and have potential for use in proficiency testing. However, there has been no formal evaluation to date to determine if digital image manipulation (intentional or unintentional) can affect their interpretation.

To investigate whether alteration of digital cytology images affects diagnosis.

Acquired digital images of ThinPrep Papanicolaou test slides were manipulated (rotated 90 degrees and brightness, contrast, red-green-blue color, and luminosity adjusted) using Photoshop. A test composed of these altered images, along with their original (unaltered) image and exact duplicates was given to 22 cytologists (13 cytotechnologists, 8 cytopathologists, and 1 fellow). All images were rated as negative, atypical (atypical squamous cells of undetermined significance), low-grade squamous intraepithelial lesion, high-grade squamous intraepithelial lesion, or positive for cancer. Weighted kappa and heterogeneity chi(2) statistics were used to measure levels of agreement and assess concordance between groups.

The level of agreement for identical duplicate images was excellent (kappa = 0.81), compared with the poor agreement for manipulated image pairs (kappa = 0.21), a statistically significant difference (P < .001). For all altered image types agreement was poor. There was no significant difference between cytotechnologists and cytopathologists in level of agreement (P = .56).

Manipulation of a Papanicolaou test digital image, irrespective of the specific category of cytologic material photographed, significantly affects its interpretation by both cytotechnologists and cytopathologists. This suggests that care needs to be taken when digital cytology images are used, to specifically ensure that their alteration does not affect diagnosis.