<qa>  What is the bronze standard benchmark?Ammonia is an important molecule relevant to numerous diseases, especially to the millions of patients with cirrhosis worldwide. Venous blood ammonia via limb phlebotomy, can at best roughly estimate whole body ammonia, but says little or nothing about intestinal production, and cannot source ammonia to any particular organ or body compartment. Unfortunately, there are no presently available better tests. Therefore, despite these acknowledged limitations, venous ammonia the bronze standard benchmark by which new metrics are assessed. 