Creatinine (F)

Question 1

What is creatinine?

Answer 1

1) It is the final product of creatine phosphate in muscles (muscle metabolism)
2) It is the index of overall renal function
3) It is solely a waste product

Question 2

What are the characteristics of creatinine?

Answer 2

1) Produced from 3 AAs: methionine, arginine, and lysine
2) Partially secreted by PCT
3) Sp but not sensitive to renal disorders
4) Not affected by protein diet

Question 3

What are the 3 AAs that are the origin of production of crea?

Answer 3

1) Methionine
2) Arginine
3) Lysine

Question 4

What are the sx considerations for creatinine testing?

Answer 4

1) Non-fasting
2) Hemolyzed sxs should be avoided
3) Cephalosporin: false increase / elevation

Question 5

What is the result of creatinine lvls if the pt is taking cephalosporin?

Answer 5

False increase / elevation

Question 6

What is the method that can be used for crea testing?

Answer 6

Chemical method (Jaffe method)

Question 7

What is the principle of chemical method (Jaffe method) for crea testing?

Answer 7

A yellow-orange tautomer of creatinine picrate is formed when crea is mixed w/ alkaline picrate

Question 8

What is the principle of rxn of chemical method (for crea testing)?

Answer 8

Creatinine + Sodium Picrate (under the presence of alkali) -> creatinine - picrate complex (yellow-orange)

Question 9

What is the working rgnt for crea testing?

Answer 9

Sodium picrate

Question 10

What is the amt of working rgnt that is used for crea testing?

Answer 10

1,000 uL

Question 11

How to create the working rgnt used in crea testing?

Answer 11

1) Combine equal volumes of creatinine picric acid rgnt and creatinine sodium hydroxide
2) Mix well

Question 12

What is the shelf life of the combined (working) rgnt?

Answer 12

It is stable for up to 1 mo

Question 13

What is the procedure (or steps) of crea testing if the principle of spectrophotometry is used?

Answer 13

1) Prepare creatinine working rgnt accdg to instructions
2) Pipette 1,000 uL working rgnt into tubes labeled “standard”, “control”, “patient”
3) Add 50 uL of sx and mix
4) After exactly 30 secs, read and record A (A1). At exactly 60 secs after reading (A1), read and record A (A2)
5) Calculate change in A (ΔA= A2 − A1) per min

Question 14

What is the procedure (or steps) of crea testing if machine is used?

Answer 14

1) Prepare creatinine working rgnt accdg to instructions
2) Pipette 1,000 uL working rgnt into tubes labeled “standard”, “control”, “patient”
3) Add 50 uL of sx and mix
4) Incubate for 2 mins
5) Feed onto your machine

Question 15

What are the reference ranges (for crea testing) for male and female?

Answer 15

Male: 0.9 - 1.50 mg/dL
Female: 0.7 - 1.37 mg/dL

Question 16

What are the causes of increased crea?

Answer 16

1) Impaired renal function
2) Chronic nephritis
3) Congestive heart failure

Question 17

What are the causes of decreased crea?

Answer 17

1) Decreased muscle mass
2) Advanced severe liver disease
3) Pregnancy
4) Inadequate protein diet