Creatinine

Keywords: Creat

Specimen:

5 mL blood in lithium heparin or plain tube.

Method:

Spectrophotometry.

Reference Interval:

Dependent on age, see Table 6.

Application:

Detection of decreased glomerular filtration. Glomerular filtration rate can be estimated (eGFR) using the CKD-EPI Algorithm.

An approximate assessment of creatinine clearance can be calculated directly from plasma creatinine using a formula (eg, Cockcroft-Gault).

See Creatinine clearance.

Interpretation:

Increased creatinine levels occur in conditions which decrease the glomerular filtration rate. These may be pre-renal (eg, hypovolaemia, hypotension), renal or post-renal (eg, obstruction).

An artefactual increase in creatinine is seen with some methods in the presence of ketones and some cephalosporins - consult pathologist.

Levels are lower in patients with a reduced muscle mass (eg, the elderly) and this may conceal impairment of renal function.

See also Table 1.

Reference:

Gault MH et al. Nephron 1992; 62: 249-256.

Eknoyan G et al. Am J Kidney Dis 2003; 42(4): 617-622.

KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney International supplements 2013;3:1-150