What do amorphous phosphates precipitate as in a refrigerated urine sample?

Amorphous phosphates are formed when urine is allowed to cool, especially in refrigerated specimens. In these conditions, excess phosphates can precipitate out of the solution, leading to the formation of a white precipitate. This occurs due to the decreased solubility of phosphates at lower temperatures, which causes them to aggregate and settle out of the urine.

In clinical practice, the presence of a white precipitate in refrigerated urine samples is generally associated with phosphates and is often a normal finding rather than an indicator of pathology. Recognizing this characteristic helps in differentiating normal sedimentation from other pathological crystals or sediments that may appear in urine.