Specimen Collection

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 ^o C
• 14 days at 2-8 ^o C
• Stable at -20 ^o C

4.5 mL PST Blood (Preferred)

0.5 mL Paediatric Micro-PST Blood (Preferred)

5 mL Heparin Blood

4 mL Plain Blood

3.5 mL Adult SST Blood

0.5 mL Paediatric Microsample Blood
Reference Intervals

Units: mmol/L

Reference Ranges:

Neonate:	4.5 - 6.0
Adult:	3.5 - 5.2

Haemolysis, prolonged standing of specimen, and squeezing of heel or finger during micro-collection may give significantly elevated levels.

Uncertainty of Measurement: 5%

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

Turnaround Time: Within 3 hours

Urgent result, 1 hour turnaround time

Assay Method

Principle: Ion selective electrode

Reagents: Roche Potassium electrode

Analyser: Cobas Indirect ISE

Diagnostic Use and Interpretation

Increased plasma potassium is seen in:

• renal failure
• potassium supplementation
• ACE inhibitors, ARBs, aldosterone blockers
• Addison's disease
• acidosis
• tumour lysis syndrome

Decreased plasma potassium is seen in:

• diuretics
• alkalosis (e.g. due to vomiting)
• chronic diarrhoea
• primary or secondary hyperaldosteronism
• treatment of diabetic ketoacidosis
• magnesium depletion

ARTEFACTUALLY INCREASED POTASSIUM

Intracellular K+ concentration is much higher than extracellular; a delay of more than 2 hours before separating the plasma can result in significant falsely increased K+ due to leakage out of cells. This effect is greater at low temperatures. Haemolysis also results in falsely increased K+

PSEUDOHYPERKALEMIA

In some patients with leukemia, K+ leaks from white cells rapidly after the sample is taken; this effect is increased by clotting. The true K+ can be obtained by taking a heparinised blood sample and immediately analysing it on a blood-gas machine.

Contact Information

Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.

If the query concerns a specific patient please include the NHI number in your email.

If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).

Individual chemical pathologists may be contacted but will not be available at all times.

After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.

Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402

Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052

Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427

Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427

Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427

Last updated at 15:26:00 06/01/2025