Creatinine Prt. 2 Flashcards
Creatinine (MW 113 Da) is the cyclic anhydride of creatine that is produced as the final product of decomposition of________.
It is excreted in the urine; measurements of ______ and its renal clearance are used as diagnostic indicators of kidney function.
phosphocreatine
plasma creatine
Creatine is synthesized in the (3)
(1) kidneys
(2) liver
(3) pancreas
Interconversion of phosphocreatine and creatine is a particular feature of the metabolic processes of______
muscle contraction
A proportion of the free creatine in muscle (thought to be between 1% and 2% per day) spontaneously and irreversibly converts to its anhydride waste product-______.
creatinine
Thus, the amount of creatinine produced each day is relatively constant end is related to the______
muscle mass
In health, the concentration of creatinine in the bloodstream also is relatively constant.
However, depending on the inclividual’s_____ intake, diet may influence the value.
meat
Creatinine is present in all body fluids and secretions, and is freely filtered by the glomerulus.
Creatinine production also decreases as the circulating level of creatinine increases;
several mechanisms for this have been proposed, including (3)
(1) feedback inhibition of production of creatine
(2) reconversion of creatinine to
(3) conversion to other metabolites
The methods most frequently used to measure creatinine are based on the_______ first described in 1886.
In this reaction, creatinine reacts with ______ in_____ solution to form a________.
Jaffe reaction
picric acid
alkaline
red-orange chromogen
Jaffe reaction was adopted for the measurement of blood creatinine by_______ in 1919.
Folin and Wu
Jaffe reaction
The reaction is nonspecific and subject to positive interference by a large number of compounds, including; AAAGP
acetoacetate
acetone
ascorbate
glucose
pyruvate
More accurate results are obtained when creatinine in a protein-free filtrate is adsorbed into______ (aluminum magnesium silicate) or_____ (sodium alurninum silicate) then eluted and reacted with alkaline picrate.
Because this method is time consuming and not readily automated, it is not used routinely.
Fuller’s earth
Lloyd’s reagent
Because this method is time consuming and not readily automated, it is not used routinely.
Fuller’s Earth
Lloyd’s reagent
Fuller’s earth
(aluminum magnesium silicate)
Lloyd’s reagent
(sodium alurninum silicate)
Two approaches have been developed to increase the specificity of assay methods for creatinine:
a kinetic Jaffe method and reaction with various enzymes.
In the________, serum is mixed with alkaline picrate and the rate of change in absorbarice is measured.
Although this method eliminates some of the nonspecific reactants, it is subject to interference by -keto (2-oxo) acids and cephalosporins.
kinetic Jaffe method
Bilirubin and hemoglobin may cause a negative bias, probably a result of their destruction in the strong base used.
The_______ is used despite these problems because it is rapid, inexpensive, and easy to perform.
kinetic Jaffe method
In kinetic Jaffe method
(2) may cause a negative bias, probably a result of their destruction in the strong base used.
Bilirubin
hemoglobin
In an effort to enhance the specificity of the Jaffe reaction, several coupled enzymatic methods have been developed.
The method using _____
was adapted for use on a dry slide analyzer.
Creatinase
Sarcosine oxidase
Peroxidase
is now used as a reference method.
Isotope Dilution Mass Spectrometry
Creatinine may be measured in
plasma, serum, or urine
____ and _____samples should be avoided, particularly if a Jaffe method is used.
Hemolyzed and icteric
_______ may yield erroneous results in some methods.
A______ is not required, although high protein ingestion may transiently elevate serum concentrations.
Lipemic samples
fasting sample
Urine should be______ after collection or
frozen if longer storage than____ days is required.
Refrigerated
4days
(4) may increase creatinine concentration measured by the Jaffe reaction, especially at temperatures above 30°C.
This interference is significantly decreased when_____ measurement is applied.
AGKU
Ascorbate
glucose
ketoacids
uric acid
kinetic
Depending on the concentration of reactants and measuring time, interference from____ may persist in kinetic Jaffe methods.
Some of these substances interfere in enzymatic methods for creatinine measurement.
ketoacids
causes a negative bias in both Jaffe and enzymatic methods.
Bilirubin
will interfere in enzymatic methods that use peroxidase as a reagent.
Ascorbate
Patients taking_____ antibiotics may have falsely increased results when the Jaffe reaction is used.
cephalosporin
______particular, is known to affect both Jaffe and enzymatic methods.
_____ causes a positive bias in some enzymatic: methods.
Dopamine
Lidocaine
