You should use the same unit for plasma uric acid and urinary uric acid, and the same unit for plasma and urine creatinine.
The excreted fraction of uric acid is used in the exploration of hyper and hypouricemia, and certain nephropathies.
Formula: It is calculated by dividing the product (urinary uric acid x serum creatinine ) by the product (blood uric acid x urinary creatinine ) and multiplying the result by 100%. Normal values are less than 10%.
Uric acid constitutes the final product of the metabolism of purine bases originating from the catabolism of nucleic acids, but also from an endogenous synthesis or from food. At physiological pH, uric acid is almost completely ionized and is present in plasma as sodium urate. Uric acid and urate are relatively insoluble molecules that easily precipitate in aqueous solutions such as urine or synovial fluid, which can cause lithiasis or arthritis.
Distribution in the body, the total pool of uric acid is distributed 80% in the extracellular fluid and 20% in the plasma.
In plasma, uric acid is more widely present in the free state, in the form of urate due to the blood pH ˃ to the value of the PKa of uric acid.
Renal elimination in 70% and 30% of digestive tract via intestinal uricolysis by intestinal bacteria Urates
unbound circulating fluids are freely filtered is eliminated in a complex way by the kidney according to 4 successive stages:
almost total glomerular filtration, proximal tubular reabsorption, proximal tubular secretion than a new distal tubular reabsorption. The fraction of uric acid excreted in the urine corresponds to 10% of the filtered load.
The processes of reabsorption and secretion are conditioned by unidirectional membrane transporters.