Creatinine

Testing Laboratory

Department

Chemical Pathology

Delphic Registration Code (Alpha Code)

SCRE

Test Code (Numeric Code)

0105

Laboratory Handling

Phlebotomy

As of 27/03/2025, the default method for creatinine testing is the enzymatic method unless specified otherwise on the lab request form. The only exceptions are paediatric ICU patients and clinical trials patients, who will continue to default to Jaffe. See the section on 'Method Differences' below for more information.

Sample Stability

Enzymatic= 7 days at 15-25°C, 7 days at 2-8°C, 3 months at -20°C, Jaffe= 7 days at 15-25°C, 7 days at 2-8°C, 3 months at -20°C

Synonyms

Serum/Plasma Creatinine

Turnaround Time

3 hours

Specimen Type

• Plasma
• Serum

Specimen Requirements

Tube/Container Type:

Preferred

• Lithium Heparin PST- Gel (Light Green Cap)

Acceptable

• Heparin (Microtainer)
• Lithium Heparin - Non-gel (Green Cap)
• Plain (Red Top)
• SST II (Gold Cap)

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Heparin (Microtainer)

Acceptable

• Plain(Microtainer)
• Lithium Heparin - Non-gel (Green Cap)
• Lithium Heparin PST- Gel (Light Green Cap)
• Plain (Red Top)
• SST II (Gold Cap)

Pre-testing Requirements

Overnight fasting samples are recommended (or no meat intake for 12 hours before sampling) but not required.

Additional Specimen Information

As of 27/03/2025, the default method for creatinine testing is the enzymatic method unless specified otherwise on the lab request form. The only exceptions are paediatric ICU patients and clinical trials patients, who will continue to default to Jaffe. See the section on 'Method Differences' below for more information.

Specimen reception:

When Enzymatic Creatinine is requested please register ECRE instead of SCRE.

When Jaffe Creatinine is requested please register CREJ instead of SCRE.

When both Creatinine Jaffe and Enzymatic Creatinine are requested, please register CREJ and ECRE.

Automation:

When there is a patient with a high bilirubin there is significant interference with the Jaffe method and clinicians will request Enzymatic Creatinine.

Test Method

Creatinine (Enzymatic)
Principle : Colorimetric

Reagents: Roche CREP2/ CREA2 kit

Analyser: Cobas c502

Creatinine (Jaffe)
Principle : Colorimetric

Reagents: Roche CREJ kit

Analyser: Cobas c502

Method differences

As of 27/03/2025, creatinine is measured by the enzymatic method except in the following circumstances:

Jaffe creatinine is specifically requested.
The patient is in PICU or NICU
The request originates from a registered clinical trial and the method is not specified (this allows continuity in existing trials).
Both methods produce similar results and method differences should not be noticeable in most cases. The enzymatic method may give ~5% higher results when the creatinine concentration in over ~2000 umol/L, but this is smaller than the expected imprecision of the test. A significant discrepancy between the methods may occur if there is an interfering factor, such as those listed in the table below.

Jaffe interferences (effect on results) Enzymatic interferences (effect on results)
Excess proteins, especially paraprotein (increase) IV lignocaine (increase)
Glucose, gross hyperglycaemia (increase) N-acetylcysteine (decrease)
Ketones (increase) Paracetamol metabolites in overdose (decrease)
Vitamin C, ascorbic acid (increase) Vitamin C, ascorbic acid (decrease)
Bilirubin, jaundice (decrease) Bilirubin, jaundice (small decrease)
HbF (decrease) Catecholaminergic inotropes/vasopressors such as noradrenaline, adrenaline, dopamine and dobutamine (decreased)
Some cephalosporins (increase)

The Jaffe method should be preferred if a patient has had recent paracetamol overdose or is receiving catecholaminergic vasopressors/inotropes. Enzymatic method should be preferred if the patient is significantly jaundiced, hyperglycaemic or ketotic.

Both methods are aligned and traceable to international standards/gold standard measurement systems and their results are almost identical most of the time, especially in healthy patients. To request a specific method, write it clearly on the request form under 'other tests', e.g. "Jaffe creatinine".

Uncertainty of Measurement

Uncertainty of Measurement (Enzymatic): 5% Uncertainty of Measurement (Jaffe): 6 umol/L at a concentration of 50 umol/L 6% at a concentration of 160 umol/L Conversion factors: mg/100 mL x 88.4 = umol/L umol/L x 0.0113= mg/100 mL

Non-Funded Test Cost

$3.19 (Exclusive of GST)

Additional Costing Information

Please be aware that prices may change. If required, confirmation of the current price can be obtained from Elaine McGrath .

Specimen reception:

When Enzymatic Creatinine is requested please register ECRE instead of SCRE.

When Jaffe Creatinine is requested please register CREJ instead of SCRE.

When both Creatinine Jaffe and Enzymatic Creatinine are requested, please register CREJ and ECRE.

Automation:

When there is a patient with a high bilirubin there is significant interference with the Jaffe method and clinicians will request Enzymatic Creatinine.

Contact Information