Blood Uric Acid Flashcards
BUA is a byproduct of _ catabolism.
purine nucleic acid
BUA is produced in the _ and filtered by _.
liver; glomerulus
BUA excreted _% in the proximal tubules.
98-100%
What is the main form of BUA in plasma?
monosodium urate
What are the clinical applications in measures BUA? (5)
- Confirm diagnosis and monitor treatment of gout
- Prevent uric acid nephropathy during chemotherapeutic treatment
- Assess inherited disorders of purine metabolism
- Detect kidney dysfunction
- Assist in the diagnosis of renal calculi
Blood uric acid is a _ (reducing, oxidizing) agent.
reducing agent.
BUA chemical method:
Based on the reduction of phosphotungstic acid in alkaline solution to tungsten blue.
Caraway method
BUA chemical method:
Caraway method is _ (nonspecific, specific) and requires protein removal.
nonspecific
Fill in the blank:
Uric acid + H3PW12O40 + O2 → ___ + tungsten blue + CO2
allantoin
In enzymatic enzyme, what enzyme is use to catalyze oxidation of uric acid to acid?
uricase enzyme
T/F:
Enzymatic methods is more specific and commonly used.
T
BUA enzymatic methods:
It measures the hydrogen peroxide produced as uric acid is converted to allantoin.
- sources of error: reducing agents (bilirubin and ascorbic acid)
Coupled enzyme reaction
BUA enzymatic methods:
The color produced is directly proportional to uric acid concentration.
Coupled enzymatic reaction
BUA enzymatic methods:
What is the source of error in Coupled Enzymatic Reaction?
reducing agents (bilirubin and ascorbic acid)
BUA enzymatic methods:
Product in the first step of Coupled enzymatic reaction:
allantoin from uric acid
BUA enzymatic methods:
Two enzymes used in Coupled enzymatic reaction:
- Uricase
- Peroxidase
BUA enzymatic methods:
What is the enzyme used in this reaction?
Uric acid + O2 + 2 H2O2 → allantoin + CO2 + H2O2
uricase
BUA enzymatic methods:
What is the enzyme used in this reaction?
2 H2O2 + 4-AAP + EHSPT → quinoneimine + HCl + 4 H2
peroxidase
BUA enzymatic methods:
It measures differential absorbance before and after incubation with uricase at 293 nm.
Spectrophotometric assay
BUA enzymatic methods:
The difference is directly proportional to uric acid concentration.
Spectrophotometric assay
BUA enzymatic methods:
What are the sources of error in Spectrophotometric assay?
- Presence of protein
- Hemoglobin
- Xanthine
BUA Determination:
This method typically uses UV detection.
High-performance liquid chromatography (HPLC)
BUA Determination:
A proposed candidate reference method, detects characteristic fragments following ionization, and quantifies uric acid using isotopically labeled compound.
Isotope Dilution Mass Spectrometry (IDMS)
Specific requirements in BUA
What is the sample needed in quick preparation?
serum sample
Specific requirements in BUA
Does the patient requires fasting?
No
Specific requirements in BUA
Three samples that are rejected in BUA:
- Hemolysis
- Lipemia
- Icteric
Specific requirements in BUA
What should we do if the samples are not processed immediately?
refrigerate
Specific requirements in BUA
What are the drugs needed to be avoided to prevent the increase values for uric acid?
- Salicylates
- Thiazides
Specific requirements in BUA
Tubes that should not be used:
- EDTA
- Sodium fluoride
Specific requirements in BUA
The urine sample must be _ (acidic, alkaline)
alkaline
What are the two Uric Acid Reagent Kit?
- Phosphate buffer (EHSPT, Amino-4-antipyrine, Uricase, peroxidase, ferrocyanide, sodium azide
- Standard Uric acid: 6 mg/dL or 0.357 mmol/L (may vary depending on manufacturer)
Assay requirements:
Wavelength
546 nm
Assay requirements:
Optical path
1 cm
Assay requirements:
Temperature
37 C
Calculation:
Concentration of Standard of Serum/Plasma:
6 mg/dL or 0.357 mmol/L
Calculation:
Concentration of Standard of Urine:
88 mg/dL or 5.235 mmol/L
Calculation:
Conversion factor from mg/dL to mmol/L:
0.0595
Reference range of plasma/serum of male (adult):
3.5-7.2 mg/dL
Reference range of plasma/serum of female (adult):
2.6-6.0 mg/dL
Reference range of plasma/serum of a child:
2.0-5.5 mg/dL
Reference range in 24-hour urine:
250/750 mg/day
Clinical significance of Hyperuricemia: (10)
- Gout
- Treatment of myeloproliferative
disease with cytotoxic drugs - Hemolytic and proliferative
processes - Purine-rich diet
- Increased tissue catabolism or
starvation - Toxemia of pregnancy
- Lactic acidosis
- Chronic renal disease
- Drugs and poisons
- Enzyme deficiencies
What are the 4 types of Enzyme Deficiencies in BUA?
- Lesch-nyhan syndrome (hypoxanthine guanine phosphoribosyltransferase deficiency)
- Phosphoribosylpyrophosphate synthetase deficiency
- Glycogen storage disease type 1 (glucose-6-phosphate deficiency)
- Fructose intolerance (fructose-1-phosphate aldolase deficiency)
Clinical significance of Hypouricemia: (4)
- Liver disease
- Defective tubular reabsorption (Fanconi syndrome)
- Chemotherapy with azathioprine or 6-mercaptopurine
- Overtreatment with allopurinol