A revalidation and critique of assumptions about urinary sample collection methods, specimen quality and contamination.

We found little evidence for contamination with the four methods. Natural void was the best method for harvesting shed urothelial cells and white blood cells. It provides a richer sample of the inflammatory exudate, including parasitised urothelial cells and the microbial substrate. However, if the midstream sample is believed to be important, the MSU collection device is advantageous.