Quality-assurance study of simultaneously sampled, non-correlating cervical cytology and biopsies.

As part of a quality assurance study, we reviewed 223 cases of simultaneously sampled cervical smears and biopsies that showed a significant lack of correlation for squamous dysplasia or carcinoma. In 153 of the 223 cases (68.6%), the cytology was negative and the biopsy positive. After review of the specimens, errors in this group were found to be of the following types: sampling 64%, interpretive 29%, and combined sampling and interpretive 7%. In the remaining 70 cases (31.4%), the biopsy was negative and the Papanicolaou smear positive. In these cases, the following types of errors occurred: sampling 54%, interpretive 33%, and combination 13%. Twenty-nine of these 70 patients showed dysplasia on follow-up material. These findings indicate there are a significant number of false-negative Papanicolaou smears, mostly because of sampling problems. There are few false-positives. In cases of positive Papanicolaou and negative biopsy, dysplasia is likely to be present in subsequent samples.