What Can Cause an Abnormal Pap Smear?

Millions of individuals get Pap smears or Pap tests every year to screen for cervical cancer. (The cervix is the lower part of the uterus, which leads into the vagina.) This simple procedure is part of a regular visit to a gynecologist. A Pap smear consists of swabbing cells off of your cervix and sending them to a lab where a specialist looks at them under a microscope to determine if they look normal or abnormal.

Pap tests can be a bit uncomfortable and sometimes a little awkward. Still, most Pap test results come back normal. However, some 2% to 5% of people who have a Pap test—named after the originator of the exam, George Papanicolaou—will have an abnormal result, Adi Davidov, MD, director of gynecology and robotic surgery at Staten Island University Hospital, told Health.

If you're one of those individuals, you're probably more than a little nervous about what "abnormal" really means. Here's what you need to know.

What Conditions Result in an Abnormal Pap Smear?

Human Papillomavirus (HPV)

For starters, abnormal cells on Pap test results do not necessarily mean you have cancer. "There can be many different reasons why a Pap smear may be abnormal," Nazia Munir, MD, a family physician at Henry Ford Health System in Detroit, told Health. "The most common is the human papillomavirus."

HPV is responsible for almost all cases of cervical cancer. But testing positive for the virus does not mean you actually have cancer. Around 90% of the time, the virus, which is sexually transmitted, clears on its own, leaving no evidence in its wake. "A lot of times patients have HPV and are completely asymptomatic," said Dr. Munir. Some people may have mild symptoms but still recover completely.

When HPV does lead to pre-cancerous or cancerous changes in cervical cells, those abnormally growing cells will be categorized as mild, moderate, or severe, Leslie McCloskey, MD, associate professor of obstetrics, gynecology, and women's health at Saint Louis University, told Health. If this happens, your healthcare provider will help you determine the best course of treatment.

Infections

Certain vaginal infections can be a potential cause of abnormal Pap smears. In a 2021 study published in the Europasian Journal of Medical Sciences, 14.39% of patients with abnormal smears experienced cervical-vaginal infections.

In a July 2020 study in the Indian Journal of Sexually Transmitted Diseases and AIDS, researchers found that 96% of the Pap smears in 50 patients were abnormal and included indications of sexually transmitted infections (STIs) such as chlamydia, gonorrhea, and trichomoniasis, among other issues.

Yeast infections, medically known as candidiasis, can also cause changes in cervical cells, resulting in an abnormal result on your Pap smear. Fortunately, all of these infections can be treated.

Other Causes of Abnormal Pap Tests

In rare instances, even inflammation—perhaps from having sex recently—can lead to an abnormal Pap test result. Additionally, menopause can produce changes in cervical cells because of dwindling estrogen levels. "When there's not that much estrogen, cells can look funny and mimic precancerous conditions," said Dr. Davidov.

What Happens if You've Had an Abnormal Pap Smear?

If your Pap results come back abnormal, your healthcare provider will want to follow up to find out what, if anything, is going on.

If you haven't had one already, your provider may order a second test that looks for HPV DNA. This will tell you if HPV is a likely cause of the abnormal results. It can even tell you if you have one of the specific strains (often HPV 16 or 18) that cause cervical cancer, though it won't say if you have the disease.

The next step is a colposcopy. Per Medline Plus, a colposcopy is when a provider looks closely at the cervix with a microscope-like device called a colposcope. A diluted vinegar solution is often applied to the cervix to temporarily change the color of any abnormal areas, making them easier for your healthcare provider to see.

Not every abnormal Pap test warrants a colposcopy, especially in younger females, Dr. McCloskey said. "Their risk of having [cervical cancer] is so low, on occasion we may just elect to repeat a Pap test in six months or a year"—to see if the results are still abnormal.

If anything looks more than mildly wrong in a colposcopy, healthcare providers will do a biopsy, which is the removal of a small sample of tissue or cells to test further in the lab, according to MedlinePlus. A biopsy will tell you specifically if you have cancer or precancerous changes. "If the biopsy result confirms that there is a precancerous condition, the patient usually requires treatment that removes the precancerous condition," said Dr. Davidov.

What Else To Know About Pap Smears

In general, people under 30 should get a Pap test every three years starting at age 21, provided their Pap smear results are normal according to MedlinePlus. From 30 to 65, individuals with normal Pap smear results should have one every three years plus an HPV test every five years with a normal test. Healthcare providers may determine that people over 65 may no longer need to have Pap smears if they've had normal Pap smears across several years or had a hysterectomy or surgical removal of their cervix due to a non-cancerous condition.

These guidelines remain true whether or not you've been vaccinated against HPV. The vaccines don't protect against all strains of HPV per the National Cancer Institute (NCI). Additionally, you may need to be screened more frequently than every three to five years or after age 65 if you are at a higher risk of cervical cancer. Per MedlinePlus, past abnormal Pap smears, an HIV diagnosis, a weakened immune system, or exposure to Diethylstilbestrol (DES)—a medicine that was prescribed for miscarriage prevention between 1940 and 1971—before you were born can all increase your cervical cancer risk.

If you happen to be pregnant when it's time for your Pap smear, the test can still be done as usual. Healthcare providers can even follow up on abnormal Pap results with a colposcopy if needed.

A Quick Review

A Pap test can tell you something might be wrong—but it can't tell you what the problem is. According to the Centers for Disease Control and Prevention, every year, nearly 12,000 women are diagnosed with cervical cancer and around 4,000 die from the disease. But most are preventable, Dr. McCloskey said, "if patients come for Paps and for the appropriate follow-up."