Both conventional and ThinPrep Papanicolaou smears with high-grade squamous intraepithelial lesions that are frequently missed are known to have relatively few abnormal cells. Whether this is also true of cases of low-grade squamous intraepithelial lesion is not known.
To compare the cytologic features of cases of low-grade squamous intraepithelial lesion that perform poorly with the features of cases that perform well.
The cytologic features of 10 ThinPrep Pap Test and conventional smear cases of low-grade squamous intraepithelial lesion that performed poorly in the College of American Pathologists Interlaboratory Comparison Program were compared with 46 ThinPrep Pap Test and conventional smear cases that performed extremely well. The numbers of abnormal cells were categorized into less than 50, 51 to 100, 101 to 250, 251 to 500, and more than 500.
The median number of abnormal cells for cases that performed poorly was less than 50, whereas the median number of abnormal cells for cases that performed well was between 101 and 250. Overall, cases that performed poorly were significantly more likely to have less than 50, less than 100, and less than 250 abnormal cells than cases that performed well (P < .001, P < .001, and P = .009, respectively). A minority of cases performed well even with very few abnormal cells and groups. The same findings were present when conventional smears and ThinPrep specimens were analyzed separately.
ThinPrep Pap Test cases and conventional smears with a diagnosis of low-grade squamous intraepithelial lesion that perform poorly in this program have significantly fewer abnormal cells than those that perform well. The median number of abnormal cells in cases that performed well is lower than that of comparable high-grade cases in the program.