What is the best method to preserve urine specimens without causing significant changes?

Refrigeration is the best method for preserving urine specimens because it slows down the metabolic processes and the growth of bacteria that can alter the composition of the urine. By cooling the sample, chemical reactions and bacterial proliferation are minimized, thus maintaining the integrity of analytes and reducing the risk of contamination or degradation.

Other methods, such as room temperature storage, could allow for the rapid growth of microorganisms and changes in urine chemistry, leading to inaccurate results when the sample is eventually analyzed. Freezing, while it can halt some processes, can also cause cellular lysis and changes in the concentration of certain solutes due to ice crystal formation. Heat treatment can denature proteins and alter other components of the urine, leading to significant changes in its characteristics. Therefore, refrigeration is the preferred method for preserving urine specimens for accurate analysis.