CC1 NPN

• one of these test is being carried out in clinical chemistry that would refer to the measurement of renal function test - urea
• the NPN compound present in the highest concentration in the blood is urea
• urea is the major excretory product of protein metabolism; it is formed in the liver from amino groups and free ammonia generated during protein catabolism
• protein metabolism produces amino acids that can be oxidized to produce energy or stored as fat and glycogen.
• during protein metabolism nitrogen is released converted to urea and excreted as a waste product
• the measurement of urea is not only to define renal function, but also give an idea about the hydration state of the patient; their nitrogen balance. It also aids the adequacy of the patient undergo dialysis
• when a patient is undergoing dialysis the urea level is undeniably high
• the most common method couples the urease reaction with glutamate dehydrogenase where the conversion of nicotinamide adenine dinucleotide at 340 nm is measured
• kinetic method urea is made to react with glutamine dehydrogenase. it is a couples reaction wherein urea will yield ammonium carbonate then the ammonia will be coupled with oxoglutarate and NADH with glutarate dehydrogenase, it will result in glutamate + NAD + hydrogen
• chemical method diacetyl monoxime is made to react with water resulting in hydroxylamine and diacetyl. The diacetyl in an acidified area will yield a yellow diazine derivative that would represent the concentration of urea in blood
• specimen requirements that could be used for urea could be plasma, serum or urine
• in urine, urea is susceptible to bacteria decomposition so specimens particularly urine should be refrigerated if not tested immediately
• fasting is not usually required in case of urea
• elevated concentration of urea in the blood - azotemia
• now very high plasma plasma urea concentration is accompanied by renal problems and renal failures the term used is uremic syndrome or urea syndrome. Uremic syndrome or urea syndrome is not treated with dialysis and kidney transplant is very fatal and can lead to death
• condition resulting in increased plasma urea concentration are classified into three main categories according to cause: prerenal, renal and postrenal
• prerenal stage is accompanied by a slightly increasing level of urea. Prerenal disorders contribute to are congestive heart failure, hemorrhage, dehydration, increased protein catabolism, high protein concentration
• renal stage; when it becomes acute and chronic renal problems, there is already renal disease. Then this is so-called glomerulonephritis, tubular necrosis, which are case that are encountered in actual renal disorders
• in the renal stage, decreased renal function causes an increased plasma urea concentration as a result of compromised urea excretion
• creatinine is a waste product of muscle concentration that is formed from phophocreatine, a high- energy compound
• creatinine levels are regulated by kidney excretion
• creatinine level are not changed by diet or rate of urine flow and not reabsorbed by renal tubules
• the sufficiency of creatinine measurement determines the severity of kidney damage. It also can be used to monitor the progression of kidney disease and the severity of kidney malfunction after medication; if the creatinine level continues to rise the medication given is not effective
• creatinine level are regulated by kidney excretion just like the blood urea nitrogen . this concept make it very useful tool in checking kidney function because creatinine levels should be excreted in the kidney
• uric acid is the final product of catabolism of purine nucleic acids
• uric acids relatively insoluble in plasma and high concentration can be deposited in the joints and tissue causing painful inflammation
• uric acid is primarily formed in the liver as the end product of purine metabolism, either through the breakdown of dietary nucleic acid or from cellular turnover
• uric acid is usually measured to confirm diagnosis and monitor treatment of gout, an arthritic condition characterized by precipitation of uric acid crystal deposition in joints and tissues
• uric acid is readily oxidized to allantoin and therefore can function as reducing agent in chemical reaction
• the most common method of this type is the caraway method, which is based on the oxidation of uric acid in a protein-free filtrate with subsequent reduction of phosphotungstic acid in alkaline solution to tungsten blue
• coupled enzymatic method measure uric acid levels by measuring the hydrogen peroxide produces as uric acid converted to allantonin
• decrease in absorbance at 293 nm measured - spectrophotometric
• uric acid may be measured in heparinized plasma, serum or urine. serum should be removed from the cells as quickly as possible to prevent dilution by intracellular contents
• uric acid is stable in plasma or serum after RBC have been removed. Serum samples may be stored refrigerated for 3 to 5 days
• an abnormal increase in plasma uric acid concentration. It is accompanied by pain and inflammation of the joints - gout
• overproduction of uric acid - hyperuricemia
• lesch-nyhan syndrome a condition that occurs almost exclusively in males, it is characterized by neurological and behavioral abnormalities and the overproduction of uric acid
• chemical methods are used to detect uric acid in samples
• creatinine is synthesized primarily in the liver from arginine, glycine and methionine
• creatinine phosphate undergoes the spontaneous loss of phosphoric acid while creatinine loses water, each independently forming the cyclic compound creatinine, which diffuses into the plasma and excreted in the urine