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

The chemical pathology team can be reached via email: chemicalpathologist@adhb.govt.nz or via Lablink (09) 307 4949 ext 22000 or 09-3078995

Emails will receive priority attention from the on-call chemical pathologist. Include the patients NHI.

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 Saku.Jayasinghe@adhb.govt.nz
• Dr Owen Yi WenyiYi@adhb.govt.nz

Last updated at 11:42:03 16/01/2026