Nonprotein Nitrogen Compounds

• Urea

  • NPN present in highest concentration
• Conversion factor of BUN to Urea: 2.14
• Reference Method for NPN: IDMS
• Urea

  Major product of protein metabolism
• Urea reacts with diacetyl to form a yellow colored compound
• Urea is 45-50% of the NPN
• Creatinine is 5% of the NPN
• Jaffe Reaction

  • Creatinine react with Alkaline picrate to produce a red-orange tautomer
• Llyods Reagent: Sodium aluminum silicate

  Fuller's Reagent: Aluminum magnesium silicate
• BUN/Creatinine Ratio: 10-20:1
• Uric acid is 10-20% of NPN
• Uric Acid

  • Product of purine catabolism
• Ammonia is 0.2% of NPN
• Ammonia

  • Produced from the catabolism or deamination of amino acids