False positive cervicovaginal cytology. A follow-up study

To determine what percentage of cervical cytologic diagnoses initially classified as false positives (based on a negative cervical biopsy within three months of the cervical cytologic smear) are recategorized as histologic false negatives when subsequent studies reveal abnormalities.

A three-year review of 1,242 cervicovaginal biopsies with corresponding cytology in the preceding three months revealed 68 cases (5.5%) where the cytology was positive for a squamous intraepithelial lesion but the biopsy was within normal limits or showed benign cellular changes. Follow-up cytologic and/or histologic diagnoses were obtained for 53 of the 68 cases from the patients' hospital and physician office records.

Of the 53 cases with follow-up, 24 (45%) were found to have a subsequent squamous intraepithelial lesion (indicating a sampling error at the time of the initial biopsy), and 9 showed atypical squamous cells of undetermined significance. In addition, 9 of the 20 patients (45%) who had negative follow-up studies had benign abnormalities on the initial, noncorrelating biopsy that may have contributed to the discrepancy.

This study emphasized the importance of diligent follow-up of patients with noncorrelating studies since they represent a population at high risk for the subsequent detection of premalignant conditions.