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ThinPrep Cytologic Test (TCT): Approved by the U.S. FDA for clinical use in 1996. The TCT test uses a liquid-based thin-layer cytology system to test cervical cells and provides a cytological classification diagnosis using TBS (The Bethesda System). It is currently the most advanced cervical cancer cytology examination technology in the world. Compared with traditional cervical smear Pap smear tests, it significantly improves the satisfaction of the specimen and the detection rate of abnormal cervical cells. The TCT cervical cytology test has a 100% detection rate for cervical cancer cells and can also detect precancerous lesions and microbial infections such as fungi, trichomonas, and chlamydia. Currently, many advanced countries such as the United States and the United Kingdom have applied TCT technology to cervical cancer screening for women.
The main method involves washing the exfoliated cervical cells into a vial containing cell preservation solution. The brush used for collecting the sample is swirled in the vial for several seconds. The sample is then filtered through a high-precision membrane to separate impurities from the epithelial cells, which are then spread in a thin layer (20 mm in diameter) on a glass slide. The cells are fixed with 95% alcohol, stained using the Pap staining method, and covered. Cytology experts examine the slides under a microscope and diagnose according to the TBS method. This method increases the diagnostic rate for abnormal cells by 13% and the detection rate for low-grade squamous intraepithelial lesions and above by 65%. However, the equipment can only handle one specimen at a time.
Liquid-Based Cytology Test (LBC): A major advancement in cytopathological diagnosis in recent years. It provides a sensitive, accurate, economical, and convenient method for the screening, follow-up, and early diagnosis of cervical cancer and precancerous lesions. This technology continues the advantages of cytopathological diagnosis, such as convenient sampling, non-invasive procedure, and reproducibility. Compared with traditional Pap cervical smears, the sensitivity and specificity of LBC diagnosis are greatly improved, reducing misdiagnosis and missed diagnosis rates.
There are revolutionary advancements in cell processing and smear preparation methods:
1. Advanced cell collection method: using a conical brush head ensures that cells from critical areas (such as the squamocolumnar junction of the cervix) are collected and transferred to the preservation solution.
2. Fixing cells in liquid avoids degradation caused by air drying, maintaining the original cell morphology.
3. Dissolving excess mucus and red blood cells, removing most white blood cells via centrifugation, maximizes the concentration of diagnostically valuable cells while reducing the obstruction of mucus, red blood cells, and white blood cells.
4. Thin-layer cell technology allows cells to be distributed evenly on the smear, preventing cell overlap and blockage, saving examination time, reducing missed diagnoses, and improving work efficiency.
5. The staining process is fully automated by computer, with each smear stained individually to avoid floating debris or cross-contamination of cells. Reagents are never reused, ensuring vivid cell staining and clear images.
Additionally, LBC uses the TBS classification method for diagnosis, which is consistent with histopathology in grading, enhancing microorganism diagnosis content to make it more comprehensive and clear.
The advent of liquid-based cytology technology represents a significant innovation in smear technology, though it does not change the viewing method (slides must still be examined manually under a microscope by cytology experts). The accuracy of diagnosis is closely related to the examiner's eye fatigue, experience level, and sense of responsibility. Thus, a critical evaluation of this new preparation technology is needed. Furthermore, the equipment requires expensive investment (including the continual purchase of cell preservation solutions), which is beyond the reach of most hospitals in China and is suitable for large hospitals in major cities with the necessary resources to adopt this new technology. Cervical cells screened by CCT and confirmed by cytology experts offer advantages such as being advanced, accurate, swift, economical, and convenient. Combining these two modern cytological techniques, where ultrathin smears are prepared using liquid-based thin-layer cytology technology followed by CCT screening, would achieve higher diagnostic accuracy. It should be noted that TCT technology cannot yet achieve this advanced combination, whereas LBC can, thus it is also known as T-CCT technology.
