What Can Cause Abnormal Pap Smear Results?

Receiving an abnormal pap smear test result can understandably stir up concern, but it's important to remember that such findings don't necessarily point to a serious health issue such as cervical cancer. As part of Cervical Health Awareness Month, we sit down with Gregory Root, D.O., an obstetrician and gynecologist (OBGYN) at INTEGRIS Health Canadian Valley Hospital to explain what abnormal results mean, shed light on the various causes behind them and guide you through the steps to take.

"Early detection is key to preventing cervical cancer,” Root says. “Although it remains the fourth most common cancer in women globally, cervical cancer does not rank among the top 10 new cancer cases in the United States, thanks to the widespread implementation of pap smear screening. This simple, effective tool has played a critical role in saving lives. When combined with the HPV vaccination, we have the potential to reduce the incidence of cervical cancer even further. By prioritizing regular screenings and vaccination, we can make cervical cancer a preventable disease for future generations."

What does a pap smear test?

What to know: A pap smear is a test to screen for cervical cancer in women. It involves collecting cells from the cervix (the lower, narrow end of the uterus that opens into the vagina). 

The primary purpose of a pap smear is to detect precancerous or cancerous cells in the cervix. 

• The test identifies abnormal changes in cervical cells that might develop into cancer if left untreated.
• A pap smear is often combined with a test for human papillomavirus (HPV), a common sexually transmitted infection that can cause cervical cancer.

During the procedure, your OBGYN uses a speculum to gently open the vagina and access the cervix.

• A small brush or spatula is then used to collect a sample of cervical cells.
• The cells are sent to a laboratory to be examined under a microscope for abnormalities.

Women should begin pap smears at age 21 and continue every three years if results are normal.

• After age 30, women may choose to have a pap smear combined with HPV testing every five years.

Learn more: Watch this video about cervical cancer screening and guidelines.

Causes of abnormal pap smear results

At a glance: An abnormal pap smear doesn’t always indicate cancer. In fact, there are several potential causes for abnormal results, ranging from infections to precancerous changes.

Precancerous changes suggest the abnormal cells have a chance of developing into cancer.

• Atypical squamous cells of undetermined significance (ASC-US) is the most common abnormal test result and indicates some cells are not normal, but it's unclear if they're due to infection, inflammation or precancerous conditions.
• Atypical squamous cells that cannot exclude high-grade squamous intraepithelial lesion (ASC-H), indicate the cells are more abnormal and there is a possibility of high-grade squamous intraepithelial lesions.
• Atypical glandular cells (AGC) indicate abnormal growths in the glandular tissue of the cervix and uterus.
• Adenocarcinoma in situ (AIS) indicates advanced lesions have been found in the glandular tissue of the cervix. 

Human papillomavirus (HPV) infection is the most common cause of changes in cervical cells that can lead to cancer.

• High-risk types such as HPV 16 and HPV 18 are most commonly associated with cancerous changes.
• Low-risk HPV types such as HPV 6 and HPV 11 can cause mild changes in cervical cells, often leading to genital warts rather than cancer.

Various infections can cause inflammation that leads to abnormal results.

• Bacterial or yeast infections cause the vaginal and cervical tissues to become inflamed and irritated, which can lead to changes in the appearance of cervical cells.
• Trichomoniasis is a sexually transmitted infection that can cause inflammation and changes in cervical cells.

Cervical dysplasia refers to the presence of abnormal cells on the surface of the cervix. 

• Low-grade squamous intraepithelial lesion (LSIL) indicates mild abnormalities and is usually considered low risk for developing into cancer.
• High-grade squamous intraepithelial lesion (HSIL) indicates more severe abnormalities that have a higher risk of progressing to cancer if untreated.

Cancerous cells may be present, especially if high-grade lesions are detected.

• Squamous cell carcinoma develops in squamous cells (the flat, thin cells lining the outer part of the cervix) and accounts for 80 to 90 percent of cervical cancer cases.
• Adenocarcinoma is less common and develops from the glandular cells (cells that line the cervical canal).

Menopause and sexual activity can also cause changes in cervical cells.

• Postmenopausal women can experience thinning of the cervical lining due to decreased estrogen.
• Sexual intercourse can sometimes cause temporary changes in cervical cells.

What to do after receiving abnormal results

Key points: If abnormal cervical cells are found on a pap smear, the next steps typically involve further evaluation to determine the cause and appropriate treatment. Your OBGYN may order a repeat pap smear, recommend HPV testing (if you haven’t already done so) or explore the abnormal cells further via a colposcopy.

A repeat pap smear is often recommended in a few months to ensure accurate diagnosis and appropriate follow up. 

• A repeat test helps confirm the presence of abnormal cells, as initial results can sometimes be affected by factors like inflammation or infection.
• It allows your doctor to monitor whether the abnormal cells persist, progress or regress over time.
• The initial sample might have been inadequate or contaminated, so a follow-up test can rule out errors.

HPV testing can provide additional information about the potential risk and appropriate management.

• HPV testing identifies the presence of high-risk HPV types, particularly types 16 and 18, which are most commonly associated with cervical cancer. 
• Without high-risk HPV, mild abnormalities often resolve naturally, reducing the need for invasive procedures.

Colposcopy is a procedure that uses a special magnifying instrument to more closely examine the cervix, vagina and vulva for signs of disease.

• During a colposcopy, a biopsy may be taken from any areas that look abnormal to determine the extent and nature of the cell changes.

Next steps: In the event of minor changes, your doctor will likely recommend regular monitoring with pap smears and HPV testing. Precancerous changes may include procedures to remove or destroy the abnormal cells, such as cryotherapy, laser therapy or a loop electrosurgical excision procedure (LEEP). If cancerous cells are detected, further evaluation and treatment recommendations by an oncologist will be necessary.

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