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Why is a clean-catch midstream urine sample used to test for urinary tract infection?

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The most common cause of urinary tract infection is invasion into the urethra of Escherichia coli, a type of bacterium that normally inhabits the bowel. — urinary tract infection The most common cause of urinary tract infection is invasion into the urethra of *Escherichia coli*, a type of bacterium that normally inhabits the bowel.

A clean-catch midstream urine sample is used to test for a urinary tract infection to ensure the accuracy of the laboratory analysis.

The primary purpose of this collection technique is to eliminate or prevent contamination of the specimen with bacteria or other microorganisms that may be present at the opening of the urethra, on the skin, or in vaginal secretions. By collecting the urine midstream, the initial flow of urine—which is most likely to contain these external contaminants—is bypassed, allowing for a more reliable assessment of the actual contents of the urinary tract.12