[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
● Detects characteristic fragment following ionization
● Quantifies creatinine using isotopically labeled
compound
Isotope Dilution Mass Spectrometry
Specimens used
plasma, serum, or urine
T/F: Fasting is not required
T
T/F: High protein ingestion may transiently elevate serum concentration, it is significant to increase creatinine level
F; not significant
T/F: Hemolysis, lipemia, and icteric samples should be avoided
T
T/F: If samples cannot be processed immediately, it can be refrigerated
T
T/F: Samples that are not processed for more
than 4 days or within 4 days can be freezed
T
Creatinine Reagent Kit R1
Picric Acid
Creatinine Reagent Kit R2
Sodium hydroxide, disodium phosphate
Standard Creatinine
2 mg/dl or 176.8 mmol/L
Ratio of R1 & R2
1:1
Set up the spectrophotometer at ___ nm
520
ASSAY REQUIREMENTS
● Wavelength:
● Optical path:
● Temperature:
● Read against _______ _____ (the blank used)
520 nm
1 cm
37 C
distilled water
Feed the solution in the machine at __ seconds, read and record absorbance as A1
10
Continue the timer and at exactly ___ seconds, read
and record again the absorbance as A2
120
T/F: With regards to creatinine concentration, it is very dependent by body mass
T
Computed to determine the glomerular filtration rate
Creatinine Clearance
Usually used to estimate the capacity of glomerulus to filter substances in the plasma
Creatinine Clearance
Used to approximate glomerular filtration rate (GFR)
Creatinine Clearance
Things that you should consider for the determination of ___________ is
○ the analyte should be or almost 100% is excreted in the urine
○ it should be endogenously produced by the body
glomerular filtration rate
Among all of our analytes, _______ is the best candidate for approximation of the glomerular filtration rate – called the creatinine clearance
creatinine
Measure of the amount of creatinine eliminated from
the blood by the kidneys
Creatinine Clearance
Male Creatinine Clearance
97-137 mL/min
Creatinine clearance unit
mL/min
Female Creatinine Clearance
88-128 mL/min
CLINICAL SIGNIFICANCE
Impaired renal function
Increased
CLINICAL SIGNIFICANCE
Acute kidney injury
Increased
CLINICAL SIGNIFICANCE
Low muscle mass
Decreased
CLINICAL SIGNIFICANCE
Chronic kidney disease
Increased
Jaffe Plasma Reference Range Female Adult
0.6 - 1.1 mg/dL / 53 - 97
umol/L
CLINICAL SIGNIFICANCE
Undernutrition
Decreased
CLINICAL SIGNIFICANCE
Muscle wasting
Decreased
CLINICAL SIGNIFICANCE
Muscular dystrophies
Decreased
Jaffe Plasma Reference Range Male Adult
0.9 - 1.3 mg/dL / 80 - 115 umol/L
Jaffe Plasma Reference Range Child
0.3 - 0.7 mg/dL / 27 - 62 umol/L
Jaffe 24 h Urine Reference Range Male
800-2000 mg/day / 7.1 - 17.7 mmol/day
Jaffe 24 h Urine Reference Range Female
600 - 1800 mg/day / 5.3 - 15.9 mmol/day
Enzymatic Plasma Reference Range Male Adult
0.67 - 1.1 mg/dL / 53 - 97 umol/L
Enzymatic Plasma Reference Range Female Adult
0.5 - 0.8 mg/dL / 44 - 71 umol/L
Enzymatic Plasma Reference Range Child
0.0 - 0.6 mg/dL / 0 - 53 umol/L
Considered as the best overall indicator of the level of kidney function
GFR
Gauged by measuring excretion of substance that is only minimally reabsorbed and secreted by the renal tubules
GFR
↑ creatine, ↑ urinary creatinine, _ plasma creatinine:
○ Muscle diseases
○ Muscular dystrophy
○ Poliomyelitis,
○ Hyperthyroidism
○ Trauma
N
most widely used marker for GFR, SINCE:
○ Produced at a constant rate
○ Not bound to protein
○ Not reabsorbed by the renal tubules
○ Only small amount is secreted by the tubules
(10%)
Creatinine
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Impaired renal function
Increased Serum Creatinine
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Chronic Nephritis
Increased Serum Creatinine
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Congestive heart failure
Increased Serum Creatinine & Decreased Creatinine Clearance
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
High cardiac output
Increased Creatinine
Clearance
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Decreased muscle mass
Decreased Serum Creatinine
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Advanced and severe liver
disease
Decreased Serum Creatinine
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Pregnancy
Decreased Serum Creatinine & Increased Creatinine
Clearance
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Burns
Increased Creatinine
Clearance
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Carbon monoxide poisoning
Increased Creatinine
Clearance
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Impaired kidney function
Decreased Creatinine Clearance
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Shock, dehydration
Decreased Creatinine Clearance
CLINICAL SIGNIFICANCE: SERUM / CREATININE CLEARANCE
Hemorrhage
Decreased Creatinine Clearance