Specimen Collection

Overnight fasting samples are recommended (or no meat intake for 12 hours before sampling)

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

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 reference ranges have been updated on the 25th September 2018

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 (Jaffe): 6 umol/L at a concentration of 50 umol/L
6% at a concentration of 160 umol/L

Uncertainty of Measurement (Enzymatic): 5%

Conversion factors: mg/100 mL x 88.4 = umol/L
umol/L x 0.0113= mg/100 mL

Serum/Plasma Creatinine for children <17yrs (adults NOT affected) will be offered at LabPLUS from 09/05/2018

The assay

From Roche Cobas "Jaffe" to Roche "enzymatic" method. This change is in line with recommendations from position statement by the Australasian Creatinine Consensus Working Group (ref 1).

NOTE Paediatric ICU and Neonatal ICU at Starship Hospital will NOT be affected - Jaffe method will continue to be used.

• Adults (age >=17 years) will NOT be affected - Jaffe method will continue to be used.
• Results from the 2 creatinine methods will not be aligned in concerto during cumulative viewing.
• Urine Creatinine, irrespective of the age of the patient, will not be affected by this change.

Both methods are aligned and traceable to international standards/gold standard measurement systems and their results are almost identical most of the time. However, should note:

a. Unlike the Jaffe method, enzymatic method does not suffer much interferences from albumin, ketones, HbF and IgG and generally yield more accurate results especially in young children.

b. On the other hand, enzymatic method can be falsely suppressed by therapeutic concentrations of IV dopamine or dobutamine, toxic concentrations of paracetamol metabolite or its antidote N-acetylcysteine. It can also be falsely raised by therapeutic concentrations of IV lignocaine. The degree of interference depends on dose and clearance rate (ref 2 and 3). Under those settings if a more accurate creatinine is required, please ring Labplus lablink to test add "Jaffe Creatinine" on the current sample or specifically write "Jaffe Creatinine" on the lab request form for the next sample.

Reference Interval: No Change (Refer to test guide for current clinical information)

References:
1. 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
2. Cobbaert CM, Baadenhuijsen H, Weykamp CW. Prime time for enzymatic creatinine methods in Pediatrics. Clin Chem 2009; 55 (3): 549-558
3. 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

Turnaround Time: Within 3 hours
Assay Method

Creatinine (Jaffe)

Principle : Colorimetric

Reagents: Roche CREJ kit

Analyser: Cobas c502

Creatinine (Enzymatic)

Principle : Colorimetric

Reagents: Roche CREP2/ CREA2 kit

Analyser: Cobas c502

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.

Last updated at 08:04:29 23/04/2024