“Ask Dr. HKSH” - Cervical Screening

Dr. NGAN Yuen Sheung, Hextan

Specialist in Obstetrics and Gynaecology

Q1. Why do I need cervical screening?

In Hong Kong, cervical cancer rates had been declining until the past decade. The recent gradual rise underlines our insufficient effort in prevention. In fact, cervical cancer is preventable mainly through two methods: vaccination and cervical screening, the latter being very important. A cervical smear (Pap smear) is one of the three types of cervical cancer screening. With the Cervical Screening Programme, the government has long been encouraging women aged 25 to 64 to undergo screening once they are sexually active. Women aged over 64 with no prior screening should also get screened.

Q2. Is cervical screening the same as a cervical smear test?

There are three screening options: smear test (Pap smear), HPV test, and a combination of both. What are their differences? In all three tests, a brush is used to collect cells from the cervix, which are then placed in a testing liquid for either smear test or HPV test.  For the third option, half of the sample is used for smear test for pathological diagnosis, while DNA is extracted from the other half for HPV test to detect "high-risk" HPV types. By combing both tests, the third option can provide comprehensive data and reduce the chances of false positive or false negative results but at a higher cost.

Q3. Does an "abnormal" screening result mean I have cancer?

No. A cervical smear (Pap smear) test result may indicate the presence of atypical cells, low-grade lesions, high-grade lesions, or possibly cancer. But a cancer result is not a cancer diagnosis. Further tests are required.

The presence of atypical cells are even less likely to indicate cancer. Atypical cells or low-grade squamous intraepithelial lesions (LSIL) are not cancer. Even high-grade squamous intraepithelial lesions (HSIL) do not necessarily mean cancer. Even if the smear result suggests cancer, it does not confirm a diagnosis, as the smear only collects cells. Further examination, specifically a colposcopy, is required. You may need colposcopy if the smear result shows LSIL or higher grade lesions, two consecutive atypical cell results within six months, or in case of atypical cells, a high-risk HPV result is obtained in an HPV test.

For HPV testing, what does an "abnormal" result mean? Among numerous HPV types, about 14 of them are of high-risk strains. There are two types of HPV tests: the first type detects the presence of one or moreof these 14 strains without specifying each type. The second type identifies whether HPV type 16 and 18, both particularly significant, are present. If HPV type 16 or 18 is detected, a colposcopy is recommended. If high-risk types other than 16 or 18 are found, a smear test may suffice. If the smear result is normal, repeat smear test a year later. If the smear shows abnormalities, even in case of atypical cells, a colposcopy is recommended.

Q4. When is a colposcopy needed? And how is it performed?

A colposcopy is necessary because it is an instrument that can magnify the cervix, and with the use of solutions like acetic acid and iodine, can identify abnormal tissues. A small amount of tissue is then taken from the same area by way of biopsy for pathological examination. Pathologists can examine the sample under a microscope and determine if one’s cervix is affected by HPV, present with low- or high-grade cell changes, or even cancerous. Based on these findings, appropriate treatment can then be planned.

Q5. When is a colposcopy needed? And how is it performed?

Low-grade lesions should be monitored for two years, during which regular smear or HPV tests must be taken. If test results remain normal or consistently show low-grade lesions, treatment may be considered after two years. If everything is normal, treatment may not be necessary. In case of high-grade lesions, treatment is recommended. As a simple, outpatient-based procedure, loop electrosurgical excision procedure (LEEP) is performed under local anaesthesia to remove part of the cervix for detecting low- or high-grade lesions, even cancer cells, withexcision of these abnormal cells, can prevent further cancer development. This is why screening is crucial—it allows early intervention to prevent cervical cancer.

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