Final answer:
A clean-catch / midstream specimen is urine collected in the middle of the stream to minimize contamination, providing a better representation for analysis. Blood in urine is usually abnormal, except for menstrual contamination.
Step-by-step explanation:
A clean-catch / midstream specimen refers to a method of collecting urine where the initial flow of urine is not collected, but the urine collected in the middle of the stream is captured for testing. This technique helps to minimize contamination from the skin and external genitals, providing a sample for analysis that better represents the urine's contents from the bladder. Firstly you need to urinate a small amount into the toilet to clear any contaminants in the urethra, then you collect the urine in the middle of the stream, and then finish urinating into the toilet. When collecting a urine sample, the presence of blood in urine is usually considered abnormal, unless it is due to menstrual contamination. The collection and excretion of urine involve the transport and storage system, which eliminates urine safely while preventing damage from its variable pH and osmolarity.