Findings to Date From the ASCUS-LSIL Triage Study (ALTS)

Abstract Controversy exists in the United States regarding the proper evaluation and management of low-grade squamous intraepithelial lesion (LSIL) and equivocal (atypical squamous cells of undetermined significance [ASCUS, now ASC-US]) cervical cytologic interpretations. To address this issue, the National Cancer Institute initiated the ASCUS-LSIL Triage Study (ALTS). ALTS is a multicenter, randomized clinical trial designed to evaluate 3 alternative methods of management, namely, immediate colposcopy, cytologic follow-up, and triage by human papillomavirus (HPV) DNA testing. This article summarizes the major findings of ALTS that have been published to date. Patients with ASCUS (n = 3488) or LSIL (n = 1572) were randomly assigned to research arms between November 1996 and December 1998, and were monitored for 2 years. The disease outcome was histologic cervical intraepithelial neoplasia (CIN) 3/cancer. The prevalence of oncogenic HPV was too high to permit effective triage of LSIL using HPV DNA testing by Hybrid Capture 2. However, for the women referred with a cytologic interpretation of ASCUS, HPV triage proved useful, with sensitivity equivalent to immediate colposcopy and a halving of colposcopic referrals. Among older women with ASCUS, HPV testing remained sensitive for detecting CIN 3 and cancer, but the referral percentage was dramatically lower compared to younger women. ALTS yielded insight into the performance of cytology and histopathology; experienced pathologists differed significantly in their interpretations of cervical abnormalities, especially histologic CIN 1 and cytologic ASCUS. Nonetheless, it was possible to distinguish a relatively uncommon type of ASCUS, equivocal for high-grade squamous intraepithelial lesion, that has a high positive predictive value for identifying women with underlying high-grade CIN. Many additional analyses are underway.