Pathology tests database

Sample and container requirements

Serum EDTA Plasma Lithium Heparin Plasma (paediatrics only)

Minimum volume required

40 µL serum/plasma

Special requirements

None

Patient preparation

None

Sample viability

Turnaround time

This assay is run throughout the day and night. The in-lab turnaround time is normally less than 24 hours. The test can be ordered as an urgent request.

Reference range

Serum creatinine: Females: 49 – 90 µmol/L Males: 64 – 104 µmol/L (Source : Abbott Diagnostics) As individuals age they usually lose muscle mass which means that if their renal function remains unaffected creatine concentration in serum should fall as we age. Conventional population based reference intervals have not usually been age stratified. The impact of this is that individuals can have creatinine concentrations within the conventional population reference range while having significant renal impairment.

Clinical guidance

Creatinine is a non-protein waste product of creatine phosphate metabolism by skeletal muscle tissue. Creatinine production is continuous and is proportional to muscle mass. The measurement is used in the estimation of glomerular filtration rate which is a sensitive indicator of chronic kidney disease. Circulating concentration will relate to the muscle mass of the individual, the volume of distribution of the creatinine, and the glomerular filtration rate (GFR). It follows that concentrations will be higher in men than women who have the same GFR as males have a larger muscle mass. It also follows that some ethnic groups will have higher or lower creatines depending on the average muscle mass within the population. Serum creatinine concentrations are used in the determination of creatinine clearance (an indicator of GFR) and estimation of the GFR utilising the 4 variable MDRD equation. Each of these derived figures can then be used to both identify and monitor chronic kidney disease. Estimation of GFR by formula is now recommended by the Department of Health in support of the Renal National Service Frame work. Creatinine clearance requires measurement of creatinine in serum and in urine.

Notes