BLOOD URIC ACID, BUA LABORATORY DETERMINATIONS (TOPIC 3 NON-PROTEINS) Flashcards
Waste product of purine (nucleic acids) catabolism.
Blood uric acid (BUA)
Uric acids are _____ in the blood and ____ in acidic urine.
monosodium urates
uric acid crystals
Excreted in the urine but ___ are reabsorbed.
90 %
When accumulated in the blood it is deposited in the tissues and joints as crystals.
Blood uric acid (BUA)
Purines are also present in foods like
liver,
dried beans,
peas and
Beer.
Matabolism of Blood Uric Acid
Purines (Guanine monophosphates)(Adenosine Monophosphates)
[Deamination and phosphorylation to form hypoxanthine]
–> Hypoxanthine or Xanthine
[Xanthine oxidase converts hypoxanthine to uric acid]
–> Uric Acid (water insoluble excreted in the urine)
[In some mammals presence of uricase enzyme converts uric acid to allantoin which is water solluble]
BUA is mainly synthesized in the
Liver
Intestines
Muscles
Kidney
Majority of BUA are reabsorbed from the kidney due to its;
Antioxidant property
Anti-neurodegenerative property
Anti-helminth activity
Uric acid can be measured in
serum, urine and plasma.
anticoagulant of choice
Avoid what anticoagulant?
and Specimen considerations
Heparin
Potassium Oxalate
Hemolysed
Lipemic
BUA determination (chemical method)
Caraway Method
Reduction of uric acid to tungsten blue by PTA
Uric Acid –(up arrow)Phosphotungstic acid,(down arrow)reduction–> allantoin + CO2+ tungsten blue
NaCO3 is added to improve specificity
Requires protein removal
BUA determination (enzymatic method)
Uricase method
Oxidation of uric acid by uricase and addition of H2O2
Uric acid –(Uricase)–> allantoin + CO2 + H2O2
BUA determination (enzymatic method)
Coupled enzyme I method
Uric Acid –(Uricase)–> allantoin + CO2 + H2O2
H2O2 + phenol + 4-aminoantipyrine –(Peroxidase)–> quinoneimine dye
Interferences : bilirubin and ascorbic acid
Used in automated machines
BUA determination (enzymatic method)
Coupled enzyme II method
Urice Acid –(Uricase)–> allantoin + CO2 + H2O2
H2O2 + ethanol –(catalse)–> H2O + acetaldehyde
Acetaldehyde + NAD –> Acetate + NADH + H+ (340 nm)
BUA determination METHOD
Sample diluted with known amount of labeled uric acid, record ratio of 2 isotope
Isotope dilution/mass spectrophotometry
BUA determination method that is highly specific
HPLC
BUA determination method Measurement of decrease absorbance at 290-293 nm due to destruction of uric acid.
Spectrophotometric
BUA normal vallues
Children
Female
Male
Conversion Factor
2-5 mg/dl
2-6
3-7
x 0.059
Clinical significance of high level of BUA
Hyperuricemia
Overproduction of uric acid and over consumption of food rich in purine, drugs and alcohol.
GOUT
Uric acid precipitates as monosodium urates crystals in joints causing pain and inflammation.
GOUT
Clinical Significance Predominant in men 40-50 years of age.
GOUT
It has been hypothesized that BUA accumulation is cause of enhance reabsorption of uric acid in the kidney and inhibits tubular secretion.
What disease?
von Gierk’s disease
Patient under chemotherapy
Due to increase breakdown of cells releasing purines
What are these?
Leukemia
Lymphoma
Multiple Myeloma
Plycythemia vera
Megaloblastic anemia
Inherited X-linked disorder.
Absence of hypoxanthine–guanine phosphoribosyl transferase.
Lesch-Nyhan syndrome (inborn error of purine metabolism).
have a high risk of developing gout.
T2DM
less common
Found in Liver disease
and Fanconi syndrome - renal type aminoaciduria
Hypouricemia
