An inconclusive Pap smear means the lab found cells that look slightly unusual but can’t determine whether the changes are meaningful. The medical term for this result is ASC-US, which stands for atypical squamous cells of undetermined significance. It’s the most common abnormal finding on a Pap test, showing up in roughly 2% of all routine screenings. In most cases, the cell changes turn out to be caused by something harmless.
Why Cells Can Look Abnormal
A Pap smear works by collecting cells from the surface of your cervix and examining them under a microscope. When those cells don’t look completely normal but also don’t look clearly precancerous, the result lands in this gray zone. Several everyday conditions can make cervical cells appear irregular without anything worrisome going on.
Common causes include vaginal yeast infections, general irritation or inflammation, and benign growths like polyps or cysts. Hormonal shifts play a big role too. Pregnancy, menopause, and low estrogen levels can all change the way cervical cells look under a microscope. For menopausal women whose HPV test comes back negative, a doctor may prescribe estrogen cream to see if the cell changes resolve once hormone levels stabilize.
Infection with certain strains of HPV (human papillomavirus) is another possibility, and it’s the one your doctor will want to rule out. HPV is the primary driver of cervical cancer, which is why the next step after an inconclusive result almost always involves HPV testing.
What Happens Next: HPV Testing
Most labs now perform what’s called reflex HPV testing. This means they automatically run an HPV test on the same sample they already collected, so you don’t need to come back for a second appointment. The lab specifically checks for high-risk HPV strains, including types 16, 18, and 45, which are responsible for the majority of cervical cancers.
Your HPV result is the single most important factor in determining what comes next. It splits the path into two very different tracks.
If Your HPV Test Is Negative
This is the outcome most people get, and it’s reassuring. When you have an inconclusive Pap but no high-risk HPV, the risk of having a serious precancerous change is very low, less than 2%. That’s essentially the same risk as someone whose Pap came back completely normal. In this scenario, you return to routine screening on a normal schedule, typically retesting in three to five years depending on your age and screening history.
If Your HPV Test Is Positive
A positive HPV result doesn’t mean you have cancer. Most HPV infections clear on their own within a year or two, especially in younger women. But it does mean closer monitoring is warranted. Current guidelines from the American College of Obstetricians and Gynecologists recommend repeating HPV testing or co-testing (HPV plus Pap) in one year for patients with minor abnormalities and a low estimated risk of precancerous changes.
If the repeat test a year later still shows HPV or abnormal cells, or if the initial results suggest a higher level of concern, the next step is a colposcopy. This is a closer examination of the cervix using a magnifying instrument, and it allows a doctor to identify specific areas that may need a small tissue sample (biopsy) for a definitive answer.
How Risk Levels Guide Your Timeline
Doctors now use a risk-based framework to decide how often you need follow-up. Rather than treating every abnormal result the same way, the system estimates your individual likelihood of having a serious precancerous change and matches it to a management plan.
- Risk below 0.15%: Return to routine screening every five years.
- Risk between 0.15% and 0.55%: Repeat testing in three years.
- Risk between 0.55% and 4%: Repeat testing in one year.
- Risk above 4%: Colposcopy is recommended.
Your risk estimate depends on your current results, your HPV status, and your screening history. Someone with an inconclusive Pap and no HPV falls into the lowest categories. Someone with an inconclusive Pap, a positive HPV test, and a previous abnormal result moves into a higher tier that calls for closer follow-up.
Inconclusive Results During Pregnancy
Getting an inconclusive Pap while pregnant is managed slightly differently. The cell changes themselves aren’t treated during pregnancy, and any further evaluation is typically postponed. In studies of pregnant patients with ASC-US results, repeat Pap smears were scheduled for three months after delivery. For results that showed more significant changes, colposcopy was deferred until at least six weeks postpartum. Pregnancy hormones commonly alter the appearance of cervical cells, making inconclusive results even less likely to signal a real problem.
Why This Result Is So Common
If you’re feeling anxious about an inconclusive result, it helps to know just how frequently this happens. ASC-US accounts for more than half of all abnormal Pap findings. In screening studies, about 3% to 6% of all Pap smears come back with some type of abnormality, and ASC-US makes up the majority of those. Most of these cases resolve without any intervention.
The Pap test is designed to be sensitive, meaning it’s built to flag anything that looks even slightly off rather than risk missing something. That sensitivity is what makes it effective at preventing cervical cancer, but it also means it catches a lot of harmless changes along the way. An inconclusive result is the screening system working as intended, casting a wide net and then using HPV testing to sort out who actually needs closer attention.