PAP TEST or PAP SMEAR

Pap test

Cytological specimen (ThinPrep) from a patient who was later diagnosed with cervical adenocarcinoma in situ. There is at least one mitosis.

The Papanicolaou test (also called Pap smear, Pap test, cervical smear, or smear test) is a screening test used in gynecology to detect premalignant and malignant (cancerous) processes in the ectocervix. Significant changes can be treated, thus preventing cervical cancer. An anal Pap smear is an adaptation of the procedure to screen and detect anal cancers.

The test aims to detect potentially pre-cancerous changes (called cervical intraepithelial neoplasia (CIN) or cervical dysplasia), which are usually caused by sexually transmitted human papillomaviruses (HPVs). The test remains an effective, widely used method for early detection of pre-cancer and cervical cancer. The test may also detect infections and abnormalities in the endocervix and endometrium.

It is generally recommended that females who have had sex seek regular Pap smear testing. The patient may also be referred for HPV DNA testing, which can serve as an adjunct to Pap testing.

Results

In the United States, most Pap results are normal, however about 2-3 million abnormal Pap smear results are found each year. Most abnormal results are mildly abnormal (ASC-US (typically 2-5% of Pap results) or LSIL (about 2% of results)), indicating HPV infection.

Typically about 0.5% of Pap results are HSIL, and less than 0.5% of results indicate cancer; typically 0.2 to 0.8% of results indicate ASCUS.

• Atypical glandular cells (AGC)
• Atypical squamous cells of undetermined significance (ASCUS)
• Atypical squamous cells of undetermined significance (ASCUS)
• Atypical squamous cells - cannot exclude HSIL (ASC-H)
• Low grade squamous intraepithelial lesion (LGSIL or LSIL)
• High grade squamous intraepithelial lesion (HGSIL or HSIL)
• Squamous cell carcinoma

Effectiveness

Prior to the introduction of the Pap test, carcinoma of the cervix was a leading cause of death in women.

Failure of prevention of cancer by the Pap test can occur for many reasons, including not getting regular screening, lack of appropriate follow up of abnormal results, and sampling and interpretation errors. Adenocarcinoma of the cervix has not been shown to be prevented by Pap tests. In the UK, which has a Pap smear screening program, Adenocarcinoma accounts for about 15% of all cervical cancers

A medical practitioner performing 200 tests each year would prevent a death once in 38 years, while seeing 152 women with abnormal results, referring 79 for investigation, obtaining 53 abnormal biopsy results, and seeing 17 persisting abnormalities lasting longer than two years. At least one woman during the 38 years would die from cervical cancer despite being screened.

Technical aspects

Unstained cells cannot be visualized with light microscopy.

The sample is then screened by a specially trained and qualified cytotechnologist using a light microscope.

• sensitivity 72%

• specificity 94%

Liquid based monolayer cytology

Once placed into the vial, the sample is processed at the laboratory into a cell thin-layer, stained, and examined by light microscopy. The liquid sample has the advantage of being suitable for low and high risk HPV testing and reduced unsatisfactory specimens from 4.1% to 2.6%. Proper sample acquisition is crucial to the accuracy of the test; clearly, a cell that is not in the sample cannot be evaluated.

Studies of the accuracy of liquid based monolayer cytology report:

• sensitivity 61% to 66%
• specificity 82% to 91%

Some, but not all studies, report increased sensitivity from the liquid based smears.

Human papillomavirus testing

Studies of the accuracy of HPV testing report:

• sensitivity 88% to 91% (for detecting CIN 3 or higher) to 97% (for detecting CIN2+)
• specificity 73% to 79% (for detecting CIN 3 or higher) to 93% (for detecting CIN2+)

By adding the more sensitive HPV Test, the specificity may decline. Due to the liquid based pap smears having a false negative rate of 15-35%, the American College of Obstetricians and Gynecologists and American Society for Colposcopy and Cervical Pathology have recommended the use of HPV testing in addition to the pap smear in all women over the age of 30.

Regarding the role of HPV testing, randomized controlled trials have compared HPV to colposcopy. HPV testing appears as sensitive as immediate colposcopy while reducing the number of colposcopies needed. Randomized controlled trial have suggested that HPV testing could follow abnormal cytology or could precede cervical cytology examination.

"A statistically significant decline in the HPV positivity rate correlated with the lifetime number of Pap smears received."

Practical aspects

The physician or operator collecting a sample for the test inserts a speculum into the patient's vagina, to obtain a cell sample from the cervix. Pap smears can be performed during a woman's menstrual period, especially if the physician is using a liquid-based test; if bleeding is extremely heavy, endometrial cells can obscure cervical cells, and it is therefore inadvisable to have a pap smear if bleeding is excessive. As abnormal endocervical cells may be sampled, those examining them are taught to recognize them.

The endometrium is not directly sampled with the device used to sample the ectocervix. Cells may exfoliate onto the cervix and be collected from there, so as with endocervical cells, abnormal cells can be recognised if present but the Pap Test should not be used as a screening tool for endometrial malignancy.

Gallery

pap test normal

pap test atropy




pap test endocervical cells




pap test citolysis




pap test trichomonas

pap test abnormal