Contamination
What is Contamination?
Urine sample contamination occurs when substances that are not part of your urine mix into the sample during collection. These substances can include skin cells, vaginal secretions, bacteria from external sources, or other materials from the genital area. Contamination is not a disease or medical condition itself. It is a technical issue that can affect the accuracy of your lab test results.
When a urine sample contains large numbers of squamous epithelial cells, it often signals contamination. Squamous epithelial cells are flat skin cells that line the urethra and genital area. A few of these cells in urine is normal. However, high numbers suggest the sample picked up cells from the skin or vaginal area during collection. This can make it harder for your doctor to interpret other test results accurately.
Contaminated samples can lead to false positive results for bacteria or white blood cells. This may cause unnecessary worry or treatment. Understanding proper collection technique helps you get clean samples and accurate results. Most contamination issues can be prevented with the right approach to sample collection.
Symptoms
Contamination itself does not cause symptoms because it is not a medical condition. However, a contaminated urine sample may show the following signs during laboratory analysis:
- High levels of squamous epithelial cells in the urine sample
- Presence of bacteria that may not actually be in the bladder
- Elevated white blood cell counts that do not reflect true infection
- Unclear or inconsistent test results that do not match your symptoms
- Cloudy or murky appearance of the urine sample
These findings appear only in lab results, not as physical symptoms you would feel. If your doctor mentions your sample was contaminated, they may ask you to provide another sample using proper collection technique.
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Causes and risk factors
Urine contamination happens during the collection process, not inside your body. The most common cause is improper collection technique. When you do not clean the genital area before collecting a sample, skin cells and bacteria can wash into the collection cup. For women, vaginal secretions can easily mix with urine if the sample is not collected using the midstream method. For men, bacteria or cells from the foreskin or tip of the penis can contaminate the sample.
Risk factors for contamination include not following clean catch instructions, using a non-sterile collection container, menstruation at the time of collection, and rushing through the collection process. Poor hand hygiene before collection can also introduce contaminants. Anyone can have a contaminated sample, but proper technique significantly reduces this risk. Understanding the correct collection method is the best way to prevent contamination and ensure your test results are accurate.
How it's diagnosed
Contamination is identified through urinalysis, a standard urine test that examines the physical and chemical properties of your urine. During microscopic examination, the lab technician counts the number of squamous epithelial cells present. Low numbers are normal, but high counts indicate the sample likely picked up cells from the skin or genital area. The technician may note the sample as contaminated in the lab report.
Rite Aid offers testing through our flagship panel at Quest Diagnostics locations nationwide. If your sample shows signs of contamination, your healthcare provider will typically ask you to provide a new sample using proper clean catch technique. This second sample usually provides clear, accurate results that can guide your care. Getting tested helps ensure your health information is reliable and actionable.
Treatment options
Since contamination is a collection issue rather than a medical condition, the solution is to collect a new sample correctly. Treatment focuses on prevention through proper technique:
- Clean the genital area thoroughly before collecting the sample
- Use the midstream collection method, letting the first part of urine go into the toilet
- Use a sterile collection cup provided by the lab or healthcare facility
- Follow all collection instructions carefully and do not rush
- Wash your hands before beginning the collection process
- For women, consider collecting when not menstruating if possible
- Ask your healthcare provider for detailed clean catch instructions if unsure
No medications or lifestyle changes are needed because contamination is not a health problem. If you repeatedly have contaminated samples despite following instructions, talk to your healthcare provider about alternative collection methods or assistance with the process.
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Frequently asked questions
A contaminated urine sample means that substances from outside your urinary tract mixed into the sample during collection. This usually includes skin cells from the genital area or vaginal secretions. Contamination does not mean you have a health problem. It simply means the lab results may not be accurate and you likely need to provide a new sample.
Your healthcare provider or lab will notify you if your sample shows signs of contamination. The lab report may indicate high levels of squamous epithelial cells, which are skin cells from the genital area. Your provider will typically ask you to collect another sample using the clean catch method. You cannot tell if a sample is contaminated just by looking at it.
Squamous epithelial cells are flat skin cells that line the urethra and genital area. A few of these cells in urine is completely normal. However, large numbers suggest the sample was contaminated during collection by skin cells or vaginal secretions. High squamous epithelial cell counts tell your doctor the sample may not give accurate information about what is happening inside your bladder.
Use the clean catch midstream method to prevent contamination. Clean your genital area with a wipe before collecting. Start urinating into the toilet, then catch the middle part of your urine stream in the sterile cup. Avoid touching the inside of the collection cup. Following these steps carefully reduces the chance of contamination significantly.
Yes, contaminated samples can show bacteria or white blood cells that are not actually in your bladder. This can suggest an infection when none exists. That is why proper collection technique matters so much. If your doctor suspects contamination, they will ask for a new sample before prescribing antibiotics or other treatments.
The clean catch method involves cleaning the genital area first, then urinating a small amount into the toilet before collecting your sample. This washes away skin cells and bacteria that could contaminate the sample. After the initial stream, you collect the middle portion of urine in a sterile cup. This gives the most accurate representation of what is in your bladder.
Most of the time, yes. Your healthcare provider needs a clean sample to make accurate decisions about your care. A contaminated sample cannot reliably show whether you have an infection, kidney problems, or other conditions. Providing a new sample using proper technique ensures your test results are trustworthy and your treatment plan is based on accurate information.
Yes, menstrual blood can contaminate a urine sample and affect test results. If possible, schedule urine testing when you are not menstruating. If you must provide a sample during your period, use a tampon or menstrual cup and follow the clean catch method carefully. Let your healthcare provider know you are menstruating when providing the sample.
No, contamination is not dangerous and does not indicate disease. It is simply a technical issue with how the sample was collected. Contamination happens outside your body during the collection process. It does not mean anything is wrong with your health. The main concern is that contaminated samples can make test results harder to interpret accurately.
You can get urine testing at Rite Aid through our testing service at Quest Diagnostics locations nationwide. We have access to around 2,000 locations for convenient testing. If your initial sample was contaminated, your provider can order a new test. Our team can help ensure you understand proper collection technique for accurate results.