Specimen Collection

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

Sample stability:

Enzymatic 7 days at 15-25 o C 7 days at 2-8 o C 3 months at -20 o C

Jaffe 7 days at 15-25 o C 7 days at 2-8 o C 3 months at -20 o C

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.

4.5 mL PST Blood (Preferred)

0.5 mL Paediatric Micro-PST Blood (Preferred)

5 mL Heparin Blood

5 mL Plain Blood

3.5 mL SST Blood

0.5 mL Paediatric Microsample Blood
Reference Intervals

Units : umol/L

Paediatric:
Birth - 7 days	<95
>7days - 4 weeks	<50
>4 weeks - 2 years	<40
>2 - 6 years	<50
>6 - 12 years	<65
>12 - 15 years	<80
>15 - 19 years (M)	<105
>15 - 19 years (F)	<90

Adult:
Male	60 - 105
Female	45 - 90

The reference interval for the first week of life is uncertain. Values up to 110 umol/L have been reported.

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

Turnaround Time: Within 3 hours
Assay 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:

1. Jaffe creatinine is specifically requested.
2. The patient is in PICU or NICU
3. 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".

Diagnostic Use and Interpretation

Plasma creatinine is increased in acute and chronic renal impairment, and any condition which reduces the glomerular filtration rate (e.g. circulatory failure; post-renal obstruction).

Creatinine is formed from creatine in muscle cells, and the plasma creatinine level is dependent on muscle mass. In patients with unusually low or high muscle mass, the plasma creatinine level and the eGFR may give a misleading indication of renal function.

Ingestion of meat or fish can raise the plasma creatinine level by up to 25 umol/L for up to 8 hours.

Drugs :

Trimethoprim and cimetidine inhibit creatinine excretion and can raise plasma creatinine by up to 44 umol/L.

Cephalosporin antibiotics can interfere in some creatinine assays, causing a falsely raised level.

References:
1. Reference intervals: ARQAG meeting 9 Oct 2008

2. Preiss et al. Influence of a cooked meat meal on estimated glomerular filtration rate. Ann Clin Biochem 2007;44:35-42.

3. Up-To-Date; 10 Sept 2015.

4. Johnson DW, Jones GRD, Mathew TH et al. Chronic kidney disease and automatic reporting of estimated glomerula filtration rate: new developments and revised recommendations. MJA 2012; 197 (4): 224-8

5. Cobbaert CM, Baadenhuijsen H, Weykamp CW. Prime time for enzymatic creatinine methods in Pediatrics. Clin Chem 2009; 55 (3): 549-558

6. Greenberg N, Roberts WL. Bachmann LM et al. Specificity characteristics of 7 commercial creatinine measurement procedures by enzymatic and Jaffe method principles. Clin Chem 2012; 58 (2): 391-40

Last updated at 12:27:22 27/03/2025