How Is a Pap Smear Read and Analyzed

How Is a Pap Smear Read and Analyzed

As soon as your Pap smear has been collected, it will be sent to the laboratory for interpretation (reading).

Since there are many labs in the US alone and each could have its own standard interpretation, a medical terminology system was created at the National Institute of Health (NIH) in Bethesda, Maryland.

The system is called The Bethesda System and allows all labs to analyze Pap smears under the same standard and produce correct results.

Back in 1988, the National Cancer Institute held a workshop to standardize Papanicolau smear results, the result is The Bethesda System. It has been improved in 2001 and now is universally accepted in the US.

Abnormal Pap smear categories

ASC-US – atypical squamous cells (thin, flat cells on the cervical surface) of undetermined significance.

This is the mildest form of cellular abnormality of the spectrum of cells from normal to cancerous. In this case the cells appear abnormal, but are not yet malignant.

One of the main causes for these cells appearing is the human papilloma virus (HPV). In most cases (80-90%) the condition is solved on its own, without treatment.

LSIL – low grade squamous intraepithelial (surface level of the cells) lesion.

Using the term lesion means abnormal tissue is being found. You might have known this as CIN grade I years ago, under the old classification.

If you have such a result on your Papanicolau test, you should consult with your gynecologist and make further investigations. Up to 30% of the women who have this result will find a more serious one once biopsy of the cervix is performed.

The course of treatment is colposcopy (examination of the cervix with a special scope) and also a cervical biopsy, which allows further sampling of the abnormal cells and finding if they are cancerous or not.


This abbreviation stands for high-grade squamous intraepithelial lesion. In the old classification it was known as CIN grade II, CIN grade III or CIS.

This is serious already, even if not cancer in all cases. High-grade squamous intraepithelial lesion means more evaluation and treatment.


It means that atypical cells are present and high-grade squamous intraepithelial lesions cannot be excluded.

Abnormal / inadequate Pap spear reports usually have the following results

Absence of endocervical cells

When your doctor uses the sampling instrument to get the cells from the inside of the cervix, called endocervical cells, it sometimes cannot reach that area. In this case the Pap smear sample won’t include these so the test cannot be properly read.

Unreliable Pap smear due to inflammation

Vaginal irritation or infections can also ruin the Pap smear interpreting.

When inflammation is present, your doctor has to first find the causes and then treat the inflammation. Otherwise it can affect both the women and her sexual partner.

Vaginal irritation can also occur, especially in menopausal women, whose bodies don’t produce estrogen in the ovaries. The vaginal walls become red and irritated and this can also affect their Pap Smear.

After the condition is treated successfully, the Pap smear is repeated.

What’s included in a Pap smear report?

Your Papanicolau test report has to include identification information, patient history and details about the specimen taken:

  • name of the woman
  • name of the pathologist reading the test
  • source of the specimen
  • last menstrual period of the woman
  • if the woman is menopausal or not
  • number of slides
  • details about the sample’s adequacy
  • final diagnosis
  • recommendation for follow-up, whether repeat or routine.

The Pap smear diagnosis takes into account

  • the patient’s history
  • sample adequacy
  • presence or absence of cellular abnormalities.

The final Pap smear diagnosis is based on three determining factors:

What to do next after a Pap smear?

If the results are good and no abnormal cells were found, your gynecologist will advise you to come for routine Pap smears.

If your Pap smear is abnormal, your doctor will come up with a list of more medical exams to be performed and a plan of treatment.