Pap Smear — Purpose, Procedure & Normal Values | MyMedicPlus

A Pap smear (Papanicolaou test, also called a cervical smear or cervical cytology test) is a routine screening procedure that collects and examines cells from the cervix — the narrow lower portion of the uterus that opens into the vagina — to detect abnormal cellular changes that may indicate pre-cancerous conditions or cervical cancer. Named after Dr George Papanicolaou, who developed the technique in the 1940s, the Pap smear has dramatically reduced cervical cancer mortality in countries where organised screening programmes exist. Cervical cancer is almost entirely caused by persistent infection with high-risk strains of human papillomavirus (HPV), particularly HPV types 16 and 18. Most modern screening programmes now combine the Pap smear with HPV primary testing — a strategy called co-testing — which significantly increases sensitivity and allows the screening interval to be safely extended to five years in women with negative results. Liquid-based cytology (LBC), in which the brush sample is rinsed into a preservative solution, has replaced conventional glass-slide smears in most countries, providing better cell preservation and enabling HPV reflex testing from the same sample.

A Pap smear is ordered as part of routine organised cervical cancer screening for all women aged 21–65 (exact age range varies by national guideline). Screening begins at age 21 in the United States regardless of sexual activity history and at age 25 in the United Kingdom. The test is also ordered diagnostically to investigate abnormal vaginal bleeding including intermenstrual bleeding, postcoital bleeding, and postmenopausal bleeding, unusual vaginal discharge, chronic pelvic pain, or a visually abnormal-appearing cervix on examination. HPV co-testing extends the recommended screening interval to 5 years for women aged 30–65 who test negative for both abnormal cervical cells and high-risk HPV. In some national programmes, HPV primary testing alone (without cytology) is now the first-line screening method. It is important to note that women who have received HPV vaccination still require regular cervical screening, as current vaccines protect against the most common but not all cancer-causing HPV strains. Women who have had a total hysterectomy for a non-cancerous indication can generally discontinue cervical screening.

Avoid scheduling the Pap smear during your menstrual period — the presence of blood and menstrual cells can obscure cervical cells and impair test accuracy, potentially producing an unsatisfactory sample requiring a repeat. For 48 hours before the test, refrain from vaginal intercourse, using tampons, douching, or applying vaginal creams, gels, lubricants, or medicines — these can wash away or obscure cervical cells. Empty your bladder before the appointment to make the examination more comfortable and allow proper positioning. You may bring a sanitary pad as light spotting can occasionally occur immediately after the procedure. Inform your doctor or nurse if you are pregnant (Pap smears are safe throughout pregnancy), have previously had abnormal smear results, have had a hysterectomy, are approaching or have entered the menopause, are on hormone therapy, or have a condition affecting the immune system such as HIV. No special dietary restrictions are needed.

You lie on your back on a gynaecological examination table with your knees bent and feet supported in stirrups (lithotomy position). The clinician — a doctor, nurse, or trained nurse practitioner — inserts a speculum, a smooth duck-billed instrument available in plastic or metal and several sizes, into the vagina. The speculum is gently opened to separate the vaginal walls and bring the cervix into view. Using a small soft nylon brush and an extended-tip spatula, or a single combined Cervex-Brush (cytobrush), the clinician collects cells from the transformation zone, which is the critical junctional area between the columnar and squamous epithelium where pre-cancerous changes almost invariably develop, and from the endocervical canal. For liquid-based cytology, the brush head is detached directly into a vial of preservative liquid. The entire cell collection procedure takes only 1–2 minutes. Mild, short-lived cramping similar to period pain is common. Light spotting for a few hours afterwards is normal. The speculum is gently removed and the appointment concludes.

Results are reported using the Bethesda System, an internationally standardised cervical cytology classification: NILM (Negative for Intraepithelial Lesion or Malignancy) — normal result, no abnormal cells detected; Unsatisfactory — insufficient cells for evaluation, repeat smear required; ASCUS (Atypical Squamous Cells of Undetermined Significance) — mildly abnormal cells, significance unclear; ASC-H (Atypical Squamous Cells — cannot exclude HSIL) — colposcopy recommended; LSIL (Low-Grade Squamous Intraepithelial Lesion) — HPV-related cellular changes, usually managed with colposcopy or repeat cytology; HSIL (High-Grade Squamous Intraepithelial Lesion) — significant pre-cancerous changes (CIN 2–3), colposcopy and biopsy required urgently; AGC (Atypical Glandular Cells) — glandular cell abnormality, requires colposcopy and endocervical sampling; Squamous Cell Carcinoma or Adenocarcinoma — cancer cells present, urgent referral for specialist treatment. Normal results are communicated within 1–2 weeks. Positive HPV co-test results are reported alongside the cytology result.

A Pap smear is a very safe procedure with an excellent safety profile. You may experience mild spotting or light bleeding and transient cramping for 1–2 days after the test — this is normal and resolves without treatment. Heavy bleeding, severe pain, or signs of infection (fever, offensive discharge) after a smear are uncommon and should prompt medical review. The main limitation of cervical cytology is its false negative rate — a well-performed Pap smear misses approximately 10–20% of significant pre-cancerous lesions (CIN 2+), usually because of sampling errors, poor cell preservation, or early lesions with minimal cellular change. HPV co-testing substantially improves sensitivity to over 95% for detecting CIN 3. Conversely, a false positive cytology result — abnormal cells on smear without underlying disease — causes unnecessary anxiety and may lead to further investigations including colposcopy and biopsy. Regular adherence to the recommended screening interval is critical, even following multiple normal results, as HPV infection can occur at any time.