02 URIC ACID Flashcards
Uric acid is the product of catabolism of ___ bases like ___ and ___
purine
adenine & guanine
___% of uric acid is reabsorbed in the proximal tubules
98-100
___% of uric acid is excreted in the distal tubules
<1
Among the excreted uric acid, ___% is excreted renally while ___% is excreted via GI tract
70
30
T/F: uric acid is soluble in plasma
F (insoluble)
Uric acid exists as monosodium urate at pH ___
7
At concentrations ___mg/dL, plasma is saturated and urate crystals may form in the tissues
> 6.8 mg/dL
At pH ___, uric acid crystals may form
< 5.75
High concentrations of uric acid may cause joints and tissue inflammation, causing ___
gouty arthritis
Level of uric acid in hyperuricemia
> 6.0 mg/dL
Deposits of crystalline uric acid, causing deformities
Tophi forms
Gout appears in male between __ and __ years old and in female after ___
30 & 50
menopausal
Treatment for increased nuclear breakdown that inhibits xanthine oxidase
allopurinol (Zytoprim)
Hemolytic anemia or megaloblastic anemia causes ___ (increase/decrease) in uric acid concentration
increase
If uric acid levels are already high, ___ may be used which oxidizes uric acid
Rasburicase
Preeclampsia and lactic acidosis causes ___ (increase/decrease) in uric acid concentration
increase
Chronic renal disease causes ___ (increase/decrease) in uric acid concentration
increase
T/F: uric acid is not a good indicator of renal function
T
X-linked genetic disorder that is caused by the complete deficiency of hypoxanthine-guanine phosphoribosyltransferase
Lesch-Nyhan syndrome
Lesch-Nyhan syndrome causes ___ (increase/decrease) in uric acid concentration
increase
In Lesch-Nyhan syndrome, lack of this enzyme prevents the reutilization of purine bases in the nucleotide salvage pathway
Hypoxanthine-guanine phosphoribosyltransferase
Fanconi syndrome causes ___ (increase/decrease) in uric acid concentration
decrease
Chemotherapy with 6-mercaptopurine or azathiopurine causes ___ (increase/decrease) in uric acid concentration
decrease
Disorder of reabsorption in the proximal convoluted tubules of the kidney
Fanconi syndrome
A nonspecific, chemical method of uric acid determination that requires protein removal
Phosphotungstic acid method
Direct redox method of uric acid determination
Caraway method/Henry’s method
A method of uric acid determination based on oxidation of uric acid in a protein-free filtrate, with subsequent reduction of phosphotungstic acid in alkaline solution
Caraway/Henry’s method
Interferences that causes a false increase in Caraway method
turbidity
aspirin and metabolites
acetaminophen
caffeine
theophylline
In iron reduction method of uric acid determination, the ___ is measured
chromophore
In the uricase method of uric acid determination, the measurement of the differential absorption of uric acid and allantoin is at what wavelength?
290-293 nm
In the uricase method of uric acid determination, Hb and xanthine would cause false ___ (increase/decrease)
decrease
T/F: one of the disadvantages of the uricase method is that it requires UV spectrophotometer
T
In the coupled enzymatic method of uric acid determination, bilirubin and ascorbate would cause false ___ (increase/decrease)
decrease
Samples allowed in uric acid determination
Heparinized plasma
Serum
Urine
T/F: diet may affect uric acid concentration
T
Interferences in uric acid determination that may falsely increase the value
Salicylate and thiazides
Additives for blood collection that are not allowed for uric acid determination
EDTA
Fluoride
pH level for urine specimen in uric acid determination
8
Normal level of uric acid in males
3.5-7.2 mg/dL
Normal level of uric acid in females
2.6-6.0 mg/dL
Normal level of uric acid in children
2.0-5.5 mg/dL
Normal level of uric acid in adult for 24h urine
250-750 mg/d
A chemical method of uric acid determination based on reduction of phosphotungstic acid in alkaline solution to tungsten blue
Caraway method
The more specific and more commonly used method of uric acid determination
Enzymatic method
An enzymatic method of uric acid determination that measures the h2o2 produced as uric acid that is converted to allantoin
Coupled enzymatic reaction
In the coupled enzymatic reaction of uric acid determination, the color produced is ___ proportional to uric acid concentration
directly
Uric acid determination:
False increase/decrease
Hemolysis =
decrease
Conversion factor of uric acid from conventional to SI unit
0.0595
