Background: To determine the reliability of repeat cervical smears (Papanicolaou smears) in patients who have had an abnormal initial smear, prospective data were collected on patients being followed up for a previously abnormal cervical smear.
Methods: All 428 patients who were referred for colposcopy because of abnormal cervical smears underwent simultaneous cervical smears and coloposcopy with directed biopsy. Patients with colposcopic evidence of invasive carcinoma or a history of prior colposcopy were excluded. Cervical smear results were compared with the histologic findings on colposcopically directed biopsy. The ability of cervical smears to identify cervical intraepithelial neoplasia (CIN) and high-grade lesions (CIN 2 and 3) were also calculated for the repeat cervical smear.
Results: The sensitivity of repeat Papanicolau screening for CIN was 48%. When differentiating high-grade lesions from low-grade and benign biopsies, the sensitivity of the repeat cervical smear was only 25%. Of 110 patients with biopsy-proven high-grade lesions, 68% had low-grade initial cervical smears and 73% had low-grade or benign repeat cervical smear cytology.
Conclusions: This study demonstrates that repeated Pap smears often fail to identify high-grade lesions and that the sensitivity of a repeat cervical smear is very low in patients with low-grade abnormalities found on routine screening examinations. Using follow-up cervical smears to monitor patients who have low-grade squamous intraepithelial lesions (LGSIL) carries unacceptable risks. A more reliable diagnostic test such as colposcopy is indicated.