When should a patient with an Atypical Squamous Cells of Undetermined Significance (ASCUS) Pap smear result get their next Pap smear?

Management of ASCUS Pap Smear Results

For patients with Atypical Squamous Cells of Undetermined Significance (ASCUS) Pap smear results, the next Pap smear should be performed in 12 months if HPV testing is not available, or colposcopy should be performed if HPV testing is positive for high-risk types. 1, 2

Management Algorithm Based on Age and HPV Testing

For Women Under 21 Years

• Repeat cervical cytology at 12 months 1
• If negative after this repeat test, perform another repeat test at 24 months
• If both tests are negative (over this 3-year period), resume routine screening
• If any repeat cytology shows ASC-US or worse, proceed to colposcopy

For Women 21-29 Years

• Option 1 (Preferred): HPV DNA testing (reflex testing) 1, 2

  • If HPV-positive: Refer for colposcopy
  • If HPV-negative: Repeat cytology in 12 months

• Option 2 (If HPV testing unavailable): Repeat cervical cytology at 6-month intervals 1, 2

  • Continue repeating every 4-6 months for 2 years until 3 consecutive negative results
  • If any repeat shows persistent ASC-US or worse: Refer for colposcopy

For Women 30 Years and Older

• Option 1 (Preferred): HPV DNA testing 1, 2

  • If HPV-positive: Refer for colposcopy
  • If HPV-negative: Return to routine screening with cotesting in 3 years

• Option 2 (If HPV testing unavailable): Repeat cervical cytology at 6-month intervals 1

  • Continue repeating every 4-6 months for 2 years until 3 consecutive negative results
  • If any repeat shows persistent ASC-US or worse: Refer for colposcopy

Rationale and Evidence

HPV triage is the preferred management strategy for ASCUS results as it is at least as sensitive as immediate colposcopy for detecting CIN grade III while referring approximately half as many women to colposcopy 1, 3. The ASCUS-LSIL Triage Study (ALTS) demonstrated this effectiveness, making HPV testing the most efficient approach 1.

For women with ASCUS who are HPV-positive, the risk of having or developing CIN II/III is approximately 15-20%, justifying colposcopy 2. Conversely, women with ASCUS who are HPV-negative have a very low risk of high-grade disease, allowing for less intensive follow-up 1.

Special Considerations

HPV 16/18 Genotyping

• If HPV genotyping is available and positive specifically for types 16 or 18, immediate colposcopy is recommended due to higher risk of progression 2
• For other high-risk HPV types, follow standard HPV-positive protocol

Pregnant Women

• Same management as non-pregnant women, but colposcopy can be deferred until after delivery unless high-grade disease is suspected

Postmenopausal Women

• Women who reach 65 years with an HPV-negative ASCUS result should be retested in 3 years and continue surveillance until they have 2 consecutive negative cotests or 3 consecutive negative Pap tests 1

Common Pitfalls to Avoid

1. Underestimating ASCUS: Despite being an equivocal finding, ASCUS can represent underlying high-grade disease in 5-10% of cases 3, 4

2. Over-management: Immediate colposcopy for all ASCUS results leads to unnecessary procedures; HPV triage is more efficient 1, 3

3. Inadequate follow-up: Loss to follow-up is a major limitation in ASCUS management, with rates as high as 27-48% reported 5

4. Documentation errors: All test results, follow-up appointments, and management decisions must be clearly documented 1, 2

5. Patient misconceptions: Many women believe they have had a Pap smear when they actually have not; clear communication about testing is essential 1

By following these evidence-based guidelines, clinicians can effectively manage patients with ASCUS Pap smear results, ensuring appropriate follow-up while avoiding unnecessary procedures.