Liquid-based cytology method

Basics of cytologic screening

The main objective of cervical cytology is the timely detection of cervical intraepithelial neoplasia (CIN). This screening has a high level of recommendation validity (A, LER 2) and is regulated by clinical guidelines for the management of patients with CIN, cervical erosion, and ectropion.

Basic rules for screening:

• Age range: the target group includes women aged 21 to 65 years. However, if a patient has been sexually active for more than three years, the test may be prescribed at an earlier age (under 21).
• Frequency: the standard interval between screenings is once every 3 years. The specific schedule also depends on age, HPV infection status, and past test results.
• Sampling rules: for the specimen to be informative, it must be taken strictly from two zones—the surface of the exocervix and the endocervical canal (provided there is no cervical canal atresia).

Comparison of conventional and liquid-based cytology

In clinical practice, two main methods of preparing cervical smear slides are used: traditional cytology and liquid-based cytology. When evaluating their efficacy for detecting high-grade lesions (CIN II and above), significant differences emerge.

Traditional cytology The classical method has extremely high specificity (96.6%), but its sensitivity is only 62.5%. The main drawback of the traditional approach is the high proportion of inadequate smears—about 10%. This is most often due to technical errors during sample collection or transfer to the glass slide.

Liquid-based cytology This method demonstrates higher sensitivity at 72.9%, although specificity is slightly lower (90.3%). The main advantage of liquid-based cytology is the dramatic reduction in the number of inadequate (non-informative) smears. As a result, the method is recognized as more effective for detecting low-grade (LSIL) and high-grade (HSIL) squamous intraepithelial lesions.

Algorithm of actions based on cytology results

Patient management tactics depend directly on the Pap test conclusion and human papillomavirus (HPV) carrier status. Today, co-testing—the simultaneous performance of cytology (or liquid-based cytology) and an HPV test—is considered the preferred screening option.

1. NILM result

Negative for Intraepithelial Lesion or Malignancy is a variant of normal.

• If cytology alone was performed, the repeat test is scheduled in 3 years.
• If co-testing was performed and the HPV test result is negative, the next co-testing can be postponed for 5 years.

2. ASC-US result and more severe lesions

Atypical Squamous Cells of Undetermined Significance requires further clarification. When ASC-US is detected, the patient is strictly indicated for HPV testing.

Further management for ASC-US depends on the presence of the virus:

• If the HPV test is negative: repeat co-testing is recommended in 3 years.
• If the HPV test is positive: the patient is referred for colposcopy, during which a cervical biopsy may be performed for histological confirmation of the diagnosis.

Management of abnormal smears

An important nuance of clinical practice relates to the physician's actions when pathological changes are detected in a cytologic specimen.

There is often an urge to quickly retake the test, but repeat smears taken within a short period of time (1.5–2 months) after the initial examination have very low reproducibility. Due to epithelial regeneration processes, a repeat result may be false-negative.

Clinical recommendation: if there are doubts or a need to clarify the diagnosis, it is advisable to request a review of the initial abnormal smears at the laboratory rather than scheduling a repeat sample collection in a short timeframe.

Class and exam questions

What else to study on this topic

• Quality criteria for sample collection from the exocervix and endocervix
• Detailed classification of lesions according to the Bethesda system (LSIL, HSIL)
• The role of HPV in the development of cervical intraepithelial neoplasia (CIN)
• Indications for colposcopy and cervical biopsy in abnormal cytology
• Principles of co-testing: advantages of simultaneous Pap test and HPV test

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