Biological variation of major gut-derived uremic toxins in the serum of healthy adult cats.

Population-based reference intervals with reference to the subject-based interval can be used to monitor serum pCS and TMAO concentrations. For IS, a subject-based and a population-based reference interval is best for short-term and medium-term monitoring, respectively. To compare serial measurements, it would be prudent to collect samples at the same time of day and consistently in either a fed or nonfed state.