Cervical Cancer Screening
Several agencies have developed guidelines on cervical cancer screening. All agree cytological screening should begin within three years of initiating sexual intercourse or age 21, which ever comes first. The American College of Obstetricians and Gynecologists (ACOG) recommend women under the age of 30 undergo annual screening. The cervix is undergoing a maturation process, increasing a woman’s risk of contracting HPV. Furthermore, high-risk behaviors are more prevalent in this age group. After age 30, women who have had 3 consecutive negative cytological screenings and no history of cervical dysplasia (CIN 2 or CIN 3), and are not immunocompromised, may undergo cytological screening every 2-3 years (56).
The upper age at which cervical cancer screening should be stopped is controversial. The American Cancer Society suggests age 70, the US Preventive Services Task Force recommends stopping at age 65 in a low risk population, but that 65-year-old women with multiple partners or a new partner continue cytological screening. The American College of Obstetricians and Gynecologists recommends individualizing the stopping of cytological screening based on the patient and her risk factors. This is due to women frequently changing health care providers; making a pap history difficult to track. While new onset cases of cervical cancer plateau at age 65, these cases occur in women who are infrequently screened. Given the controversy, it is probably an acceptable practice to stop screening pap smears in women at age 70 who have had three consecutive normal pap smears. All agencies recommend stopping cytological screening in a woman who has undergone a hysterectomy for benign indications and has no history of cervical dysplasia.
It is important to emphasize that decreasing the frequency of cervical cytological screening, or stopping it altogether, does not eliminate the need for other preventive health maintenance accomplished during an annual examination. Therefore, it is still recommended that women undergo frequent examinations, including a pelvic examination (56).
Methods of Cervical Cancer Screening
Conventional pap smears collect the exfoliated cells from the ectocervix and endocervical canal. These cells are transferred to a glass slide and fixed. The sensitivity of this test is reportedly between 50-98% (57). Errors can occur in the collection of the cells and in the laboratory evaluation of the specimen. These errors account for the false negative results obtained in pap screening. It is important patient preparation be emphasized to help optimize the collection of cells, which include the following:
· Cells should be collected before the bimanual exam.
· Avoid contaminating the speciment with lubricant
· STD testing should be done after cervical cytology collection.
· Routine swabbing of the cervical discharge should be discouraged.
The specimen should be transferred to the slide and fixed as quickly as possible. Laboratory error occurs in the interpretation of the specimen and is compounded by the inconsistencies in the cytopathologists. The 1998 Clinical Laboratory Improvement Amendment mandated that a technician could only read 100 specimens in a day and each laboratory should rescreen at least 10% of the negative results.
Newer techniques have been developed to reduce the error in the sampling and in the laboratory evaluation of specimens. Furthermore, with the knowledge that a majority of cervical cancers are precipitated by HPV infection, tests are being developed that can take advantage of this. Currently, the liquid based Pap smear is an improvement over the conventional Pap smear, which decreases the number of unsatisfactory smears taken. It also increases the detection of high-grade lesions and allows for HPV testing, without recollecting cells.
The 2001 Consensus conference readdressed the Bethesda system of nomenclature of Pap smear results, addressed the use of HPV testing, and presented algorithms for the management of abnormal pap smears (59). The current algorithms can be found at www.asccp.org
One of the most important changes in screening was the addition of HPV testing. It is the preferred method of testing for Atypical Squamous Cells – Undetermined Significance (ASC-US).