Urine Squamous Epithelial Test

When your urine is examined under a microscope, one of the first things the lab checks for is squamous epithelial cells. These are flat, scale-like cells shed from the skin around the genitals and the very end of the urinary tract. Finding a lot of them in your sample is not a sign that something is wrong with your kidneys or bladder. It is a sign that skin cells got mixed in during collection, which can make every other result on your urinalysis less trustworthy.

That distinction matters more than most people realize. If your sample is heavily contaminated with these cells, a positive test for bacteria or white blood cells might not mean you have an infection. And a reading that shows blood in your urine might just be an artifact of a poorly collected specimen. Knowing your squamous epithelial cell count helps you and your provider decide whether to act on the rest of the urinalysis or repeat it with a cleaner sample.

What These Cells Actually Tell You

Squamous epithelial cells (often abbreviated SECs on lab reports) line the surfaces of your external genitalia and the outermost portion of your urethra (the tube that carries urine out of your body). They are constantly shedding, just like skin cells everywhere on your body. When you collect a midstream urine sample, some of these cells can wash into the cup, especially if the collection technique is not precise.

The presence of these cells does not reflect kidney health, bladder function, or infection. It reflects how much contact the urine stream had with surrounding skin on its way into the collection container. A study of over 19,000 emergency department urine samples found that squamous epithelial cells are a poor standalone predictor of whether a urine culture will come back contaminated, with diagnostic accuracy only modestly above chance (an AUC of about 0.68, where 1.0 would be perfect and 0.5 is random chance).

Why a High Count Undermines Other Results

The real clinical impact of squamous epithelial cells is indirect. When many of these cells are present, the accuracy of the other markers on your urinalysis drops. In a study of over 6,400 emergency department patients, the presence of squamous epithelial cells reduced how well standard urinalysis markers could predict a positive urine culture for infection.

A large study of nearly 19,400 urine samples quantified this effect. When fewer than 8 squamous epithelial cells appeared per low power field (a standard microscopy view), urinalysis markers like white blood cells and bacteria had a positive likelihood ratio (a measure of how much a positive result raises the odds of true infection) of about 5 to 6 for predicting true bacterial infection. When more than 8 cells were present, that number dropped to about 2.3 to 2.4, meaning the same positive findings were far less reliable.

What this means for you: if your lab report shows a high squamous epithelial cell count alongside abnormal findings like bacteria or white blood cells, those abnormal findings may not be real. Before starting antibiotics or undergoing further testing, a repeat sample collected more carefully can save you from unnecessary treatment.

Hematuria Screening in Women

This marker has a specific role in evaluating microscopic hematuria (small amounts of blood in the urine that you cannot see with the naked eye). In women being evaluated for hematuria, a study comparing voided midstream samples with catheter-collected samples (where a thin tube is inserted into the bladder to collect urine directly) found that catheter specimens had essentially no squamous epithelial cells above 2 per high power field (a higher-magnification microscopy view). Using a cutoff of 2 or fewer cells per high power field as the definition of a properly collected sample improved how accurately the urinalysis detected true hematuria.

If you are a woman whose urinalysis shows both blood and a high squamous epithelial cell count, repeating the test with improved collection technique (or, in a clinical setting, with catheterization) can help determine whether the blood is genuinely coming from your urinary tract or is simply contamination from surrounding tissue. This can prevent an unnecessary workup that might include imaging or cystoscopy (a procedure where a small camera is inserted into the bladder to look for abnormalities).

Reference Ranges

Squamous epithelial cells do not have health-based reference ranges in the way that cholesterol or blood sugar do. There is no "optimal" number that predicts better long-term health. The numbers reported on your lab result are operational cutoffs that help judge sample quality, not your biology. Different labs may use slightly different thresholds depending on whether they use traditional microscopy or automated flow cytometry (a technology that uses a laser to rapidly count and classify cells).

These thresholds come from studies of emergency department and hospital populations and vary by sex and analytic method. Your lab may report results in different units or use slightly different cutoffs. The key principle is the same everywhere: the more squamous epithelial cells present, the less you should trust the rest of that urinalysis.

Sex Differences

Women consistently have higher squamous epithelial cell counts than men on voided urine samples. This is an anatomical fact, not a health concern. The shorter female urethra and proximity to the vaginal and vulvar epithelium mean more skin cells enter the urine stream during collection. Flow cytometry research from a study of over 2,500 samples confirmed this, establishing sex-specific thresholds: roughly 21 cells per microliter for women and 5 cells per microliter for men as indicators of probable contamination.

Older patients and those with lower body mass tend to have fewer squamous epithelial cells in their samples, based on data from a study of over 19,000 specimens. These demographic patterns do not change the clinical meaning of the result. They simply reflect how much skin contact occurs during collection.

When Results Can Be Misleading

Because this marker is fundamentally about collection quality, the biggest confounder is collection technique itself. A rushed or careless midstream catch will almost always show more squamous epithelial cells, regardless of your health status. Other factors that can inflate the count include:

• Not cleaning the genital area before collection, which allows more skin cells and bacteria to wash into the sample.
• Collecting the initial part of the urine stream rather than the midstream portion. The first few seconds of urination flush cells from the urethra and surrounding skin.
• Vaginal discharge mixing with the urine sample in women, which can introduce both squamous cells and bacteria that mimic infection on lab markers.
• Delay between collection and analysis. If the sample sits at room temperature for hours, cells can degrade or bacteria can multiply, further distorting the results.

Tracking Your Results Over Time

Unlike biomarkers that reflect ongoing health processes, squamous epithelial cells do not have a meaningful trend to track over months or years. A high count today and a low count next month does not mean your health changed. It means you collected the second sample more carefully.

That said, if you are monitoring another urine marker over time, such as protein, blood, or white blood cells for a kidney or bladder condition, consistently checking that your squamous epithelial cell count is low on each sample gives you confidence that your trend data is real. If one sample in a series suddenly shows high squamous cells alongside a jump in protein or blood, the simplest explanation is a collection issue, not disease progression. Repeat that sample before reacting.

What to Do With an Abnormal Result

A high squamous epithelial cell count is not a diagnosis. It is a flag that says "this sample may not be trustworthy." Your next steps depend on what the rest of the urinalysis shows.

• If you have a high SEC count with no other abnormalities: no action is needed. The sample was a bit contaminated but there is nothing concerning to follow up on.
• If you have a high SEC count with positive white blood cells, bacteria, or leukocyte esterase (an enzyme released by white blood cells): repeat the urine collection with meticulous midstream technique before assuming you have a urinary tract infection. Those positive findings may be artifacts of contamination.
• If you have a high SEC count with blood detected: especially if you are a woman being evaluated for microscopic hematuria, repeat with careful collection. One study found that using a threshold of 2 or fewer squamous cells per high power field as the definition of a clean sample improved the accuracy of hematuria screening.
• If repeated clean samples still show abnormalities: at that point the findings are more likely real, and further investigation, such as a urine culture, imaging, or referral to a urologist (urinary tract specialist) or nephrologist (kidney specialist), is warranted.