Potassium (Blood)

Testing Laboratory

Auckland Te Toka Tumai | Auckland Hospital

Department

Chemical Pathology

Delphic Registration Code (Alpha Code)

SK

Test Code (Numeric Code)

0101

Laboratory Handling

Phlebotomy

Please Note: If extended electrolytes are requested only Na, K and Cl will be registered. If other tests are required please specify.

Sample Stability

14 days at 15-25°C, 14 days at 2-8°C, Stable at -20°C

Associated Tests

• Renal Function Tests (Blood)

Synonyms

Plasma Potassium, Serum Potassium, K, K+, Renal function tests

Turnaround Time

3 hours

Urgent result, 1 hour turnaround time

Specimen Type

• Plasma
• Serum

Specimen Requirements

Tube/Container Type:

Preferred

• Lithium Heparin PST- Gel (Light Green Cap)

Acceptable

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

Preferred Sample Volume (ml)

5

Minimum Sample Volume (ml)

3.5

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Lithium Heparin PST- Gel (Light Green Cap)

Acceptable

• Plain (Red Top)

Preferred Sample Volume (ml)

0.5

Minimum Sample Volume (ml)

0.5

Additional Specimen Information

0.5 mL Paediatric Microtainer PST Blood (Preferred)
0.5 mL Paediatric Microtainer Plain Blood

Test Method

Performed in: LabPlus Automation
Principle: Ion selective electrode
Reagents: Roche assay
Analyser: Roche Cobas

Limitations / Interference

The measured potassium level rises over time until the blood cells are separated from the rest of the sample. This is due to leakage from the high K concentration intracellular space to the lower K concentration plasma. Therefore breakdown of blood cells can give a falsely high result. This is usually caught by the lab by the haemolysis check. However, this cannot occur in leukaemia, where leakage is rapid and not clearly detectable.

A falsely high level may occur when there is contamination with EDTA (e.g. incorrect order of draw) or from intravenous fluid with added K.

Uncertainty of Measurement

5%

** For Whole Blood Uncertainty of measurement refer to the Blood Gases page

Contact Information