From the Guidelines
ASCUS on a Pap smear stands for Atypical Squamous Cells of Undetermined Significance, indicating minor cell changes that don't clearly suggest precancerous changes, and the recommended follow-up is reflex HR-HPV testing, as it reduces the number of patients referred for colposcopy and overall cost of evaluation 1.
Definition and Implications
ASCUS is the most common abnormal Pap test result, comprising approximately 2 million of the 3.5 million abnormal Pap results reported in the United States each year 1. The cumulative risk of CIN II or III is somewhere between 6.4% and 11.9%, and the risk of invasive cancer is between 0.1% to 0.2% (1/1,000–2/1,000) 1.
Follow-up Strategies
The National Cancer Institute’s ASCUS and LSIL Triage Study (ALTS) evaluated three different management strategies for patients with these Pap smears, and found that a single enrollment HPV test identified 92.4% of all women diagnosed with CIN III 1.
- Reflex HR-HPV triage for women with ASC reduces the number of patients referred for colposcopy because the HR-HPV negative patients are returned to routine screening 1.
- HPV dramatically reduced the number of women referred to colposcopy to 55.6% as compared with 67.1% referred with repeat cytology 1.
- Triage also eliminates the delay in diagnosis of CIN III that necessarily occurs in a repeat cytology schema 1.
Recommendations
Based on the ALTS study and other data, reflex HR-HPV testing should be considered in evaluating women with ASC, as it is a more sensitive and cost-effective approach than repeat cytology 1. The alternative is two-repeat cytology every 6 months, but this approach has a lower sensitivity and may delay diagnosis 1.
From the Research
Definition of ASCUS on Pap Test
- ASCUS stands for Atypical Squamous Cells of Undetermined Significance, which is a result of a Pap test that indicates some abnormal cells were found, but they do not appear to be cancerous or pre-cancerous 2, 3, 4, 5.
- ASCUS is a common result, and most women with this result do not have cervical cancer or pre-cancerous cells 2.
Prevalence of ASCUS
- According to a study published in 1999, approximately 5-10% of women with ASCUS harbor serious cervical disease 2.
- Another study published in 2016 found that among 1,219 patients with ASCUS, the rate of detection of cervical intraepithelial neoplasia (CIN) and cancerization was 22.89% 4.
Management of ASCUS
- Human papillomavirus (HPV) DNA testing can help identify women with ASCUS who have underlying high-grade squamous intraepithelial lesions (HSIL) 2, 3, 4, 5.
- A study published in 1998 found that HPV testing alone or in combination with a repeat Pap smear can help detect CIN 2/3 in women with ASCUS 3.
- Another study published in 2019 found that the use of local estrogen therapy in post-menopausal women with ASCUS and HPV positive results can increase the specificity of the HPV test 5.
Clinical Value of HPV Detection in ASCUS
- HPV DNA detection can help categorize and manage ASCUS patients, as it can identify those who are at higher risk of developing cervical cancer or pre-cancerous lesions 4.
- A study published in 2016 found that among 601 patients with ASCUS who underwent HPV testing, 182 were positive for high-risk HPV, and the most common high-risk types were HPV16 and HPV58 4.