[2S] UNIT 9.3 Creatinine Flashcards
Formed from creatine and creatine phosphate
Creatinine
Product of muscle catabolism
Creatinine
99% excreted in urine
Creatinine
Creatinine is filtered in?
Glomerulus
3 Factors affecting creatinine level
Muscle Mass
Creatine Turnover
Renal Function
Creatine loses _____ to form a cyclic compound known as creatinine
water
Creatine phosphate loses _______ ____
phosphoric acid
↑ muscle mass _ creatinine level
↑
↑ plasma creatinine _ glomerular filtration rate
↓
CLINICAL APPLICATIONS
T/F: Determine the sufficiency of kidney function
T
CLINICAL APPLICATIONS
T/F: Determine the severity of heart damage
F; kidney damage
CLINICAL APPLICATIONS
T/F: Monitory progression of kidney disease
T
ANALYTICAL METHODS
● Most frequently used method
● First described in 1886
Chemical Methods Based of Jaffe Reaction
ANALYTICAL METHODS
Principle: In alkaline medium: Creatinine + picric acid → Creatinine-picrate complex (orange red)
Chemical Methods Based of Jaffe Reaction
ANALYTICAL METHODS
The intensity of orange red product is directly proportional to amount of creatinine present
Chemical Methods Based of Jaffe Reaction
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
Creatinine in a protein-free filtrate is adsorbed onto
fuller’s earth (aluminum magnesium silicate) or
Lloyd’s reagent (sodium aluminum silicate), then
eluted and reacted with alkaline picrate
Jaffe w/ Adsorbent
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
Non-specific and prone to false positive reactions
with:
○ Ascorbic acid
○ Glucose
○ Glutathione
○ Alpha-keto acids
○ Uric acid
○ Cephalosporins
Folin-Wu Method (w/o Adsorbent)
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
Creatinine in protein-free filtrate reacts with alkaline
picrate to form colored complex
Folin-Wu Method (w/o Adsorbent)
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
Measuring multiple absorbance
Jaffe Kinetic
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
The rate of change in absorbance is measured to
avoid interference of non-creatinine chromogens
Jaffe Kinetic
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
Not routinely used because it is time consuming and
not readily automated
Jaffe w/ Adsorbent
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
False positives
○ Alpha-keto acids
○ cephalosporins
Jaffe Kinetic
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
Routinely performed because
○ Inexpensive
○ Rapid
○ Easy to perform
Jaffe Kinetic
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
Serum is mixed with alkaline picrate
Jaffe Kinetic
ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION
False negatives
○ Bilirubin
○ Hemoglobin
Jaffe Kinetic
ENZYMATIC METHODS
● Adapted for use as dry slide method
● Potential to replace Jaffe reaction
Creatininase - H2O2
ENZYMATIC METHODS
● False positives
○ lidocaine
● False negatives
○ Ascorbic acid - interfere with peroxidase reaction
Creatininase - H2O2
ENZYMATIC METHODS
Uses series of enzymatic catalyzed reaction
Creatininase - H2O2
ENZYMATIC METHODS
○ Conversion of Creatinine to creatine
○ First enzyme used for analysis
Creatininase
ENZYMATIC METHODS
Lacks sensitivity and not used widely
Creatininase-CK
ENZYMATIC METHODS
Creatine to sarcosine and urea
Creatinase
ENZYMATIC METHODS
Sarcosine is oxidized to form formaldehyde,
glycine, and peroxide
Sarcosine oxidase
ENZYMATIC METHODS
○ Measured via peroxidase reaction
○ Peroxidase reaction will produce water and oxygen
Peroxidase
ENZYMATIC METHODS
○ The oxygen released is used to oxidize the indicator (colorless substrate)
○ Once the indicator is oxidized, it will form a
colored product
Peroxidase
ENZYMATIC METHODS
● As NAD+ is produced, it is measured as a decrease in
absorbance
● Reduction in NADH is the one being measured
Creatininase-CK
ENZYMATIC METHODS
Decrease in the absorbance is proportional to the level of creatinine in the sample
Creatininase-CK
● Accepted reference method
● Highly specific
Isotope Dilution Mass Spectrometry