Basics of screening and sample collection
The main goal of cytological screening is the timely detection of CIN. The evidence level for these recommendations is extremely high: A (LE 2).
The standard examination interval is 3 years for the target group (women aged 21 to 65 years). However, the test may be prescribed to patients under 21 if they have been sexually active for more than three years.
To obtain an adequate result, the material must be collected strictly from two sites:
- Exocervix (vaginal part of the cervix).
- Endocervix (cervical canal, provided there is no atresia).
Co-testing—a combination of cytological examination (traditional or liquid-based) and a human papillomavirus (HPV) test—is currently recognized as the most preferred screening format.
Comparison of methods: traditional and liquid-based cytology
Both methods are used to detect CIN II+, but they have different analytical characteristics.
| Characteristic | Traditional cytology | Liquid-based cytology |
|---|---|---|
| Sensitivity | 62,5% | 72,9% |
| Specificity | 96,6% | 90,3% |
| Main disadvantage | About 10% of smears are inadequate due to sampling or preparation errors | Requires special equipment |
| Main advantage | High specificity | Drastic reduction in the number of inadequate smears |
Due precisely to high-quality sample preparation, liquid-based cytology demonstrates higher efficacy in detecting low-grade (LSIL) and high-grade (HSIL) lesions.
Action algorithms based on PAP test results
Patient management tactics depend on the cytological conclusion and HPV status.
1. NILM result
NILM (Negative for Intraepithelial Lesion or Malignancy) indicates the absence of intraepithelial lesions or malignancy.
- Isolated PAP test: repeat the examination in 3 years.
- Co-testing (PAP test NILM + negative HPV): repeat co-testing is indicated in 5 years.
2. ASCUS result
ASCUS (Atypical Squamous Cells of Undetermined Significance). For this result, as well as for more severe lesions, HPV testing is strictly indicated.
Further management for ASCUS:
- Negative (-) HPV test: repeat co-testing is scheduled in 3 years.
- Positive (+) HPV test: the patient is referred for colposcopy with possible cervical biopsy.
Management of abnormal smears
In clinical practice, there is often a desire to quickly retake a "bad" analysis. However, repeat smears taken within 1.5–2 months after the initial examination have very low reproducibility.
Clinical recommendation: if it is necessary to clarify the diagnosis, it is advisable to have the initial abnormal glass slides re-evaluated in the laboratory rather than re-collecting material in a short timeframe. This helps avoid false results associated with traumatized epithelium.
The "3–5–3" interval rule: normal PAP test — follow-up in 3 years; normal co-test — in 5 years; ASCUS without HPV — follow-up in 3 years.
Class and exam questions
Why is liquid-based cytology considered preferable to traditional cytology?
It drastically reduces the percentage of inadequate (uninformative) smears. This increases the sensitivity of the method and makes it more effective for detecting precancerous changes (LSIL and HSIL).
What should a gynecologist do when receiving an ASCUS result?
It is necessary to assess the patient's HPV status. If HPV is detected, colposcopy is indicated (possibly with a biopsy). If there is no HPV, routine co-testing is scheduled in 3 years.
Can a PAP test be repeated a month after detecting atypia?
No, this is inadvisable. Smears taken after 1.5–2 months have low reproducibility. It is recommended to request a re-evaluation of the primary specimen in the laboratory.
At what age should cytological screening begin?
The target group starts at age 21. However, screening can begin earlier if the patient has been sexually active for more than 3 years.
What else to study on this topic
- Management of patients with detected LSIL and HSIL
- Indications and technique for colposcopy
- Features of sample collection in cervical canal atresia
- Criteria for cytological smear adequacy
- Interpretation of HPV testing results
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