Biochemical Measurements in Renal Disease Flashcards
What characteristics make for an ideal marker of GFR?
- Constant rate of appearance
- Freely filtered at glomerulus
- Not reabsorbed from renal tubule
- Not secreted into renal tubule
- Doesn’t undergo extra-renal elimination
- Easy to measure
- Endogenous
Why does urea concentration flucuate?
It is produced from protein breakdown so is higher after meals
Creatinine is a product of what?
Muscle protein breakdown
In which way is creatinine not a practical marker for GFR?
It is secreted, to a minor degree, into the renal tubule
This means the full amount cannot be determined
It is used as a marker
As creatinine _______ GFR _______
As creatinine rises GFR falls
In which instance is creatinine not sensitive to changes in GFR?
When GFR is not significantly reduced?
(it rises exponentially with reducing GFR)
What is meant by the term clearance?
Volume of plasma theoretically cleared of a substance per minute
Which factors can influence normal creatinine level?
Muscle mass
Diet
Age
Sex
Ethnicity
Why does eGFR compensate for the innaccuracies associated with a serum creatinine clearance?
Takes into account age, sex and ethnicity
Why is eGFR not perfect?
It becomes inaccurate as kindey fucntion (and GFR) improves
What is the most accurate way to measure GFR?
51Cr-EDTA clearance
In which three ways can proteinuria be measured?
- 24-hour collection
- Protein/creatinine ratio (spot sample)
- Urinalysis (dipstick) - least accurate
What is the gold standard of proteinuria?
24 hour collection
What is microalbuminaemia?
Excretion of albumin in abnormal quantities which are not significant enough to be pircked up on dipstick
Significant glomerular damage can be identified at urine protein production above which levels?
>150mg/day
