A contaminated urine sample contains foreign materials (bacteria, skin cells, or secretions) that were not present in the urinary tract itself. This contamination typically occurs during collection, introducing external elements from the surrounding genital area or hands into the specimen. The presence of these elements can lead to inaccurate test results, potentially causing a false-positive diagnosis, especially for a urinary tract infection (UTI). Ensuring the sample is accurate is important because misdiagnosis can result in inappropriate antibiotic treatment, delayed care, or unnecessary medical interventions.
Preparation Before Sample Collection
Before collection, thoroughly wash your hands with soap and water to minimize the transfer of bacteria to the collection kit. Handle the collection cup carefully, ensuring you do not touch the inside rim or the inner surface of the container or its cap. Since the container is sterile, contact with any non-sterile surface introduces a high risk of contamination.
The next step involves cleansing the genital area using the provided antiseptic wipes, a process that differs slightly based on anatomy. For females, the labia should be separated with one hand and the area wiped from front to back, using a fresh wipe for each side and then the center. This front-to-back motion is designed specifically to prevent the transfer of fecal bacteria into the collection area.
For males, the tip of the penis should be cleansed with a wipe, moving in a single motion away from the urethral opening. If uncircumcised, the foreskin must be retracted before wiping and held back throughout the entire collection procedure. This careful preparatory cleaning removes surface microorganisms that could otherwise wash into the sample and compromise the test results.
Mastering the Midstream Clean Catch Technique
The “midstream clean catch” method collects urine representing what is inside the bladder, bypassing bacteria near the urethral opening. Begin by urinating directly into the toilet. This initial flow flushes out residual organisms or cellular debris from the first part of the urethra, which is a common source of contamination.
After allowing a small amount of urine to pass, the stream should be momentarily paused or slowed. While maintaining the flow, carefully place the sterile collection cup into the stream to catch the middle portion of the void. Collect enough urine to fill the container about halfway. Avoid overfilling the cup, which increases the risk of spillage and contact with your hands.
Collect the urine that comes out after the initial flush and before the stream is finished. Throughout the collection, avoid letting the rim of the cup touch the genital area, skin, or hands. Once the required amount is collected, remove the container from the stream, and pass the remaining urine into the toilet. This technique ensures the specimen is primarily composed of urine from the bladder, free from external contaminants.
Handling and Storage After Collection
Immediately after collection, seal the cup tightly by screwing the cap on securely to prevent leakage or external contamination. Label the container clearly with your full name, the date, and the time of collection. Accurate labeling ensures the sample can be correctly tracked and processed by the laboratory.
The integrity of the sample depends on handling between collection and lab analysis, especially for a urine culture. Bacterial growth multiplies rapidly at room temperature, potentially leading to a false-positive result. Ideally, the sample should be delivered to the testing facility and processed within one hour of collection if kept at ambient temperature.
If immediate transport is not possible, the sample must be refrigerated at a temperature between 32°F and 39°F (0°C–4°C). Refrigeration significantly slows down bacterial growth, maintaining the sample’s integrity for a longer period. When stored in a refrigerator, a urine sample typically remains suitable for culture testing for up to 24 hours.