Which Infections Can the Pap Test Detect? Everything You Need to Know
Which infections does the Pap test detect?
This is a crucial question for all women who care about their gynecological health. The Pap test is a simple, quick, and painless screening exam that can literally save lives by significantly reducing mortality from cervical cancer.
During a routine gynecological visit, this important test not only shows what the Pap test reveals in terms of cellular changes, but also what the Pap test can detect beyond cancer. In fact, it can identify several infections, including HPV (the main cause of cervical cancer), bacterial infections, fungal infections such as Candida, and even non-specific inflammatory conditions.
It is also important to understand how the Pap test is performed so you can be well prepared for your appointment. Current guidelines recommend starting screening at age 25 and repeating it every 3 years, or every 5 years when combined with HPV DNA testing for women aged 30 to 64.
In this article, we will explore all the infections that the Pap test can detect, how the exam is performed, and what to do in case of a positive result. Although results are usually available within 3 weeks, it is essential to understand that a positive outcome simply indicates the presence of abnormal cells that may require further investigation—not necessarily cancer.
Which Infections Can the Pap Test Detect?
The Pap test is a screening exam that goes beyond detecting cervical cancer. Let’s look at which infections it can reveal through cytological analysis.
HPV Infections (Human Papillomavirus)
HPV is the primary cause of cervical cancer. During the Pap test, abnormal cells caused by HPV infection can be detected. There are more than 100 HPV types, but only certain high-risk strains—especially HPV 16 and 18—significantly increase cancer risk.
The Pap test detects cellular changes caused by HPV, while the HPV test directly identifies viral DNA. HPV-related abnormalities may appear as low-grade (LSIL) or high-grade (HSIL) squamous intraepithelial lesions.
Bacterial Infections (e.g. Gardnerella vaginalis)
Gardnerella vaginalis causes bacterial vaginosis (BV), the most common vaginal infection among women of reproductive age, affecting 20–60%. On Pap testing, it is identified through clue cells—epithelial cells covered with bacteria.
Fungal Infections (e.g. Candida)
Candida albicans can be detected through Pap test staining. About 75% of women experience a Candida infection at least once. Although sensitivity varies, fungal structures can be identified and may cause cellular changes unrelated to cancer.
Non-HPV Viral Infections (e.g. Herpes Simplex Virus)
Herpes simplex virus (HSV) can sometimes be identified cytologically. Infected cells show characteristic features such as multinucleation, glassy nuclei, and Cowdry inclusions. HSV may mimic cervical cancer in rare cases, even in immunocompetent patients.
Non-Specific Inflammation
The Pap test can reveal cervical inflammation, indicated by white blood cells. Persistent inflammation may require further evaluation, as studies show an increased incidence of cervical intraepithelial neoplasia (CIN) in some cases.
How the Pap Test Is Performed and What It Shows
1. Preparation for the Test
To ensure accurate results:
- Schedule the test about 2 weeks after the start of your last period
- Avoid sexual intercourse for 24–48 hours beforehand
- Avoid vaginal douches, creams, medications, or tampons
Fasting is not required, and the test can be done during breastfeeding.
2. Sample Collection
During the exam, the gynecologist inserts a speculum to visualize the cervix. A spatula or cervical brush is rotated 360° to collect cells. The procedure takes only a few minutes and causes minimal discomfort.
3. Laboratory Analysis
Cells are fixed, stained using the Papanicolaou technique, and examined under a microscope. Results are reported using the Bethesda System.
4. Conventional vs. Liquid-Based Pap Test
- Conventional Pap test: Cells are smeared directly on a slide
- Liquid-based cytology (LBC): Cells are suspended in a preservative solution, producing cleaner, more accurate samples
LBC has higher detection rates for squamous and glandular lesions.
5. Normal and Abnormal Findings
Abnormal results may include:
- ASC-US (atypical squamous cells of undetermined significance)
- LSIL (low-grade lesions, often HPV-related)
- HSIL (high-grade lesions with cancer potential)
- AGC (atypical glandular cells)
Regular screening makes cancer detection at this stage rare.
Pap Test, HPV Test, and NIPT: Key Differences
Pap Test vs. HPV Test
- Pap test: Detects abnormal cellular changes
- HPV test: Detects viral DNA
HPV testing has higher sensitivity (94.6%) compared to Pap testing (55.4%).
When to Use Each Test
- Ages 21–24: Pap test every 3 years
- Ages 25–65: Primary HPV test every 5 years, co-testing every 5 years, or Pap test every 3 years
Vaccinated women should still follow screening guidelines.
Co-Testing
Combining Pap and HPV tests reduces false negatives and improves detection of glandular lesions.
What Is the NIPT?
The Non-Invasive Prenatal Test (NIPT) analyzes fetal DNA in maternal blood to assess the risk of chromosomal abnormalities such as:
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 13 (Patau syndrome)
It is a prenatal screening test and unrelated to gynecological cancer screening.
What to Do If Your Pap Test Is Positive
Understanding the Bethesda System
Abnormal results include:
- ASC-US
- LSIL
- ASC-H
- HSIL
- AGC
Most abnormalities are not cancer.
When Colposcopy Is Needed
Colposcopy is recommended for:
- HSIL or ASC-H
- HPV-positive ASC-US
- Persistent abnormalities
- AGC
A biopsy may be performed if necessary.
Follow-Up and Treatment
- Mild lesions (CIN 1): often monitored
- Moderate/severe lesions (CIN 2–3): treated with procedures such as LEEP, conization, cryotherapy, or laser therapy
Long-term follow-up (up to 25 years) is recommended.
Conclusion
The Pap test is a fundamental tool for women’s health, detecting not only cervical cancer but also infections such as HPV, Gardnerella, Candida, and HSV.
Understanding the difference between Pap testing, HPV testing, and prenatal screening (NIPT) empowers women to make informed decisions. Most importantly, a positive Pap test rarely means cancer—it usually signals the need for monitoring or preventive treatment.
Following screening guidelines allows early intervention and effective protection of cervical health.
