[2S] UNIT 9.3 Creatinine

Formed from creatine and creatine phosphate

Product of muscle catabolism

99% excreted in urine

Creatinine is filtered in?

3 Factors affecting creatinine level

Creatine loses _____ to form a cyclic compound known as creatinine

Creatine phosphate loses _______ ____

↑ muscle mass _ creatinine level

↑ plasma creatinine _ glomerular filtration rate

CLINICAL APPLICATIONS T/F: Determine the sufficiency of kidney function

CLINICAL APPLICATIONS T/F: Determine the severity of heart damage

CLINICAL APPLICATIONS T/F: Monitory progression of kidney disease

ANALYTICAL METHODS ● Most frequently used method ● First described in 1886

ANALYTICAL METHODS Principle: In alkaline medium: Creatinine + picric acid → Creatinine-picrate complex (orange red)

ANALYTICAL METHODS The intensity of orange red product is directly proportional to amount of creatinine present

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

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

ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION Creatinine in protein-free filtrate reacts with alkaline picrate to form colored complex

ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION Measuring multiple absorbance

ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION The rate of change in absorbance is measured to avoid interference of non-creatinine chromogens

ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION Not routinely used because it is time consuming and not readily automated

ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION False positives ○ Alpha-keto acids ○ cephalosporins

ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION Routinely performed because ○ Inexpensive ○ Rapid ○ Easy to perform

ANALYTICAL METHODS: CHEMICAL METHODS BASED OF JAFFE REACTION Serum is mixed with alkaline picrate