Visual estimates of nucleus-to-nucleus ratios: can we trust our eyes to use the Bethesda ASCUS and LSIL size criteria?

BACKGROUND

Apart from several subjective criteria, ASCUS and LSIL are defined by nuclear enlargement of 2.5x to 3x and > or = 3x the area of a normal intermediate squamous cell nucleus, respectively. The aim of this study was to assess the ability of observers with various degrees of experience to estimate nuclear area ratios.

METHODS

Forty-five participants (5 anatomic pathologists, 5 cytopathologists, 2 cytopathology fellows, 16 pathology residents, 8 cytotechnologists, 6 medical students, and 3 cytopreparatory staff members) judged the area ratios of pairs of squamous cell nuclei imaged at x100 objective magnification. For Test 1 (T1), participants chose between 5 preset area ratios (1.0x to 1.4x, 1.5x to 1.9x, 2.0x to 2.4x, 2.5x to 2.9x, 3.0x to 3.4x) for 15 pairs of cells with ratios falling in the middle of these intervals. One week after T1, an instructional tutorial was given and T1 was repeated in different order of cell pairs as Test 2 (T2).

RESULTS

The kappa values for all participants were 0.30 for T1 and 0.39 for T2. Accurate responses were given in 50.5% in T1 and 53.5% in T2. Both T1 and T2 responses failed to differentiate between area ratios corresponding to ASCUS and LSIL. There were no differences in accuracy according to sex, experience, or expertise in cytopathology.

CONCLUSIONS

The overall accuracy of participants in estimating nuclear area ratios was low, especially for ratios in the range of ASCUS versus LSIL, with only minimal improvement after an instructional tutorial. Nuclear area ratio estimation may, therefore, contribute to the well-known substantial variability in ASCUS rates and ASC/squamous intraepithelial lesion ratios.