(FINAL) CC1 LAB L2

2/3

Blood Uric Acid

• Approximately ____ is excreted by the kidneys and —— by the gastrointestinal tract, where uricase-producing bacteria degrade it

1/3

Blood Uric Acid

• Approximately —— is excreted by the kidneys and ____ by the gastrointestinal tract, where uricase-producing bacteria degrade it

7.4

Blood Uric Acid

• In plasma, uric acid exists mainly as monosodium urate at physiologic pH (~____)

Purine

Blood Uric Acid

• Uric acid is the major end product of __________ metabolism in humans

Allantoin

Blood Uric Acid

• Humans lack the enzyme uricase, so uric acid is not further broken down into _________ (unlike in most other mammals)

Gout

___________ is caused by excess uric acid in the blood (hyperuricemia), which leads to crystal formation in joints

Hyperuricemia

Step-by-step mechanism of gout

1. Increased uric acid (__________)

• due to:

  • ↑ production (high purine diet, cell breakdown)

  • ↓ excretion (kidney impairment, most common cause)

Urate crystals

Step-by-step mechanism of gout

2. Crystal formation

• uric acid in blood → forms monosodium __________

• happens when levels exceed solubility

Big toe

Step-by-step mechanism of gout

3. Crystal deposition in joints

• crystals settle in joints (commonly the ________)

• cooler temperatures in extremities favor deposition

WBCs (especially neutrophils)

Step-by-step mechanism of gout

4. Inflammatory response

• immune system detects crystals as “foreign”

• __________ attack → release inflammatory mediators

Acute gout attack

Step-by-step mechanism of gout

5. __________

• sudden severe pain, redness, swelling, warmth

Chronic gout

Step-by-step mechanism of gout

6. __________ (if untreated)

• repeated attacks → permanent joint damage

• formation of tophi (visible urate deposits under skin)

3.5–7.2

Reference Intervals for BUA

• Plasma or Serum:

  • male: ______ mg/dL

  • female: ——— mg/dL

  • child: ——— mg/dL

• Urine (24 hours):

  • adult: ——— mg/day

2.6–6.0

Reference Intervals for BUA

• Plasma or Serum:

  • male: ——— mg/dL

  • female: ______ mg/dL

  • child: ——— mg/dL

• Urine (24 hours):

  • adult: ——— mg/day

2.0–5.5

Reference Intervals for BUA

• Plasma or Serum:

  • male: ——— mg/dL

  • female: ——— mg/dL

  • child: ______ mg/dL

• Urine (24 hours):

  • adult: ——— mg/day

250-750

Reference Intervals for BUA

• Plasma or Serum:

  • male: ——— mg/dL

  • female: ——— mg/dL

  • child: ——— mg/dL

• Urine (24 hours):

  • adult: ______ mg/day

Hyperuricemia

__________:

• Increased uric acid in blood

• Causes:

  • Overproduction of uric acid

  • Decreased renal excretion (most common)

  • HGPRT deficiency (Lesch–Nyhan syndrome)

  • Renal disease or impaired kidney function

  • High purine intake or increased cell turnover (e.g., malignancy, chemotherapy)

Renal excretion

Hyperuricemia:

• Increased uric acid in blood

• Causes:

  • Overproduction of uric acid

  • Decreased ________ (most common)

  • HGPRT deficiency (Lesch–Nyhan syndrome)

  • Renal disease or impaired kidney function

  • High purine intake or increased cell turnover (e.g., malignancy, chemotherapy)

Lesch–Nyhan syndrome

Hyperuricemia:

• Increased uric acid in blood

• Causes:

  • Overproduction of uric acid

  • Decreased renal excretion (most common)

  • HGPRT deficiency (__________)

  • Renal disease or impaired kidney function

  • High purine intake or increased cell turnover (e.g., malignancy, chemotherapy)

Chemotherapy

Hyperuricemia:

• Increased uric acid in blood

• Causes:

  • Overproduction of uric acid

  • Decreased renal excretion (most common)

  • HGPRT deficiency (Lesch–Nyhan syndrome)

  • Renal disease or impaired kidney function

  • High purine intake or increased cell turnover (e.g., malignancy, __________)

Hypouricemia

__________ (rare)

• Decreased uric acid in blood

• Causes:

  • Severe liver disease (↓ production of uric acid)

  • Defective renal tubular reabsorption (e.g., Fanconi syndrome)

  • Xanthinuria (xanthine oxidase deficiency)

  • Drug-induced: allopurinol, uricosuric drugs

Severe liver disease

Hypouricemia (rare)

• Decreased uric acid in blood

• Causes:

  • __________ (↓ production of uric acid)

  • Defective renal tubular reabsorption (e.g., Fanconi syndrome)

  • Xanthinuria (xanthine oxidase deficiency)

  • Drug-induced: allopurinol, uricosuric drugs

Renal tubular reabsorption

Hypouricemia (rare)

• Decreased uric acid in blood

• Causes:

  • Severe liver disease (↓ production of uric acid)

  • Defective __________ (e.g., Fanconi syndrome)

  • Xanthinuria (xanthine oxidase deficiency)

  • Drug-induced: allopurinol, uricosuric drugs

Xanthinuria

Hypouricemia (rare)

• Decreased uric acid in blood

• Causes:

  • Severe liver disease (↓ production of uric acid)

  • Defective renal tubular reabsorption (e.g., Fanconi syndrome)

  • __________ (xanthine oxidase deficiency)

  • Drug-induced: allopurinol, uricosuric drugs

Uricase

Enzymatic __________ Method (Preferred/Reference Method)

• uric acid + O₂ + H₂O —(__________)→ allantoin + CO₂ + H₂O₂

• __________ oxidizes uric acid to form allantoin and hydrogen peroxide (H₂O₂)

• The amount of H₂O₂ produced is proportional to the uric acid concentration

Catalase

Coupled enzyme reactions:

• __________ method:

  • H₂O₂ + reagent —(__________)→ colored compound

• Peroxidase method (more commonly used):

  • H₂O₂ + chromogen (indicator dye) —(peroxidase)→ colored compound

• The intensity of the color formed is directly proportional to the uric acid concentration

• Measured spectrophotometrically

Peroxidase

Coupled enzyme reactions:

• Catalase method:

  • H₂O₂ + reagent —(catalase)→ colored compound

• __________ method (more commonly used):

  • H₂O₂ + chromogen (indicator dye) —(__________)→ colored compound

• The intensity of the color formed is directly proportional to the uric acid concentration

• Measured spectrophotometrically

Phosphotungstic Acid

__________ Reduction Method (Caraway Method)  – This is a non-specific method

• Uric acid reduces __________ in an alkaline medium to form tungsten blue

• Reaction:

  • uric acid + __________ —(alkaline medium)→ allantoin + tungsten blue

• The intensity of the blue color formed is directly proportional to the uric acid concentration

• Measured spectrophotometrically (usually around 700 nm)

• Other reducing substances (e.g., glucose, ascorbic acid, bilirubin) may interfere → falsely increased results

• Largely replaced by the enzymatic uricase method (more specific)

700

Phosphotungstic Acid Reduction Method (Caraway Method)  – This is a non-specific method

• Uric acid reduces phosphotungstic acid in an alkaline medium to form tungsten blue

• Reaction:

  • uric acid + phosphotungstic acid —(alkaline medium)→ allantoin + tungsten blue

• The intensity of the blue color formed is directly proportional to the uric acid concentration

• Measured spectrophotometrically (usually around ____ nm)

• Other reducing substances (e.g., glucose, ascorbic acid, bilirubin) may interfere → falsely increased results

• Largely replaced by the enzymatic uricase method (more specific)

Enzymatic uricase method

Phosphotungstic Acid Reduction Method (Caraway Method)  – This is a non-specific method

• Uric acid reduces phosphotungstic acid in an alkaline medium to form tungsten blue

• Reaction:

  • uric acid + phosphotungstic acid —(alkaline medium)→ allantoin + tungsten blue

• The intensity of the blue color formed is directly proportional to the uric acid concentration

• Measured spectrophotometrically (usually around 700 nm)

• Other reducing substances (e.g., glucose, ascorbic acid, bilirubin) may interfere → falsely increased results

• Largely replaced by the __________ (more specific)

3–5, 2–8

Specimen Requirements

• Specimen: serum or plasma (heparin is acceptable anticoagulant)

• Avoid hemolysis

• Avoid gross lipemia

• High bilirubin concentration may interfere with results

• Stable for ____ days at ____ °C

• Recent intake of purine-rich foods may increase uric acid levels

Heparin

Specimen Requirements

• Specimen: serum or plasma (__________ is acceptable anticoagulant)

• Avoid hemolysis

• Avoid gross lipemia

• High bilirubin concentration may interfere with results

• Stable for 3–5 days at 2–8 °C

• Recent intake of purine-rich foods may increase uric acid levels

Purine-rich foods

Specimen Requirements

• Specimen: serum or plasma (heparin is acceptable anticoagulant)

• Avoid hemolysis

• Avoid gross lipemia

• High bilirubin concentration may interfere with results

• Stable for 3–5 days at 2–8 °C

• Recent intake of __________ may increase uric acid levels

C = (Cₛ × A_sample) / A_standard [mg/dL]

Calculation of BUA

• Formula:

____________________

• C = concentration of uric acid in the sample

• Cₛ = concentration of the standard

• A_sample = absorbance of the sample

• A_standard = absorbance of the standard

Normal and abnormal controls

Quality Control Reminder

• Always check if the result is within control limits before releasing

• Ensure both __________ fall within the acceptable range

• If controls are out of range → do not report results; troubleshoot and repeat the test

Isotope dilution mass spectrometry

Detection of characteristic fragments following ionization; quantification using an isotopically labeled compound

Proposed reference method!