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Quality assurance in cytology. Rescreening of previously negative smears from high grade squamous intraepithelial
S Howell1, M Theodor, N F Pacey
1Institute of Clinical Pathology and Medical Research, Westmead Hospital, Sydney, Australia.
Objective:
To determine the problem areas in the cytologic diagnosis of high grade squamous intraepithelial lesion (HSIL) (cervical intraepithelial neoplasia [CIN] 3).
Study Design:
Previously negative smears from cases with histologically proven CIN 3 in 1988 and 1992 were reviewed for any discrepancies between the original and reviewed diagnoses. Such features as the presence of excessive inflammation, blood or bacteria, and atypical and dysplastic cellular changes were assessed. Original and reviewed reports for both years were compared, and the false negative rate was calculated.
Results:
In the 1992 study, small numbers of abnormal cells, abnormal cells masked by inflammation and pale-staining HSIL were the common patterns when the diagnosis of HSIL was initially overlooked. In the 1988 study, the abnormal cells were overlooked mainly because of suboptimal smears.
Conclusion:
Determining cytologic patterns that pose problems in the diagnosis of HSIL is a valuable quality assurance procedure used in our laboratory. In performing these studies, we are able to pinpoint problem areas and educate our staff so as to minimize the number of false negative smears.