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Potassium, Plasma

K

Test Codes

EPIC: LAB6620, Beaker: KPL

Department

Chemistry

Instructions

• If an increase in platelets or leukocytes is suspected as a cause of hyperkalemia, a heparin tube should be obtained for plasma potassium.
• Blood should be obtained with as little venous stasis (i.e. tourniquet time) as possible. Fist clenching may result in false elevation of potassium.

Specimen Collection Criteria

Collect (preferred specimen): One Dark Green-top Lithium Heparin tube. (Minimum Whole Blood: 2.0 mL)

Also acceptable: One Light Green-top PST tube. (Lithium Heparin plasma gel separator tube).
One Dark Green-top Sodium Heparin tube. Contact Laboratory for acceptability of other tube types.

Caution: Never refrigerate collection tube prior to centrifugation. This may cause a falsely elevated potassium. 

Physician Office/Draw Specimen Preparation

Centrifuge tube immediately to separate plasma from cells. Transfer 2.0 mL plasma to a plastic transport tube and refrigerate (2-8°C or 36-46°F) within two hours of collection. (Minimum: 1.0 mL)

Preparation for Courier Transport

Transport: 2.0 mL plasma, refrigerated (2-8°C or 36-46°F). (Minimum: 1.0 mL)

Rejection Criteria

• Moderate to grossly hemolyzed specimens.
• Inadequately centrifuged tubes.
• Green-top tubes with plasma not separated from cells within two hours of collection.

In-Lab Processing

Centrifuge to separate plasma from cells. Deliver immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Centrifuged Green-top Tubes
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Plasma Specimens (Aliquots)
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 7 days

Plasma Specimens (PSTs)
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Performed

Sunday – Saturday, 24 hours a day.
STAT results available within 1 hour of receipt in the Laboratory.
Routine results available within 4 hours.

Reference Range

Adult range: 3.5 – 5.2 mmol/L.

Age related reference range:

Age	Range (mmol/L)
0 – 1 day	5.0 – 7.5
2 days – 3 months	4.0 – 6.0
4 months – Adult	3.5 – 5.2

Test Methodology

Potentiometric.

Interpretation

• Spuriously increased levels may be seen:
  1. Following excessive hand clenching prior to phlebotomy.
  2. If the needle (or Vacutainer^®) has been inserted into an EDTA tube prior to the tube used for potassium analysis.
  3. If whole blood sample is refrigerated prior to separation of plasma from red cells.
  4. In a hemolyzed sample.
  5. With significantly increased platelet or leukocyte counts if serum is used.
• Hyperkalemia (increased potassium): May occur in a number of conditions including renal failure, adrenal insufficiency, acidosis, malignant hyperthermia and with use of potassium-sparing diuretics.
• Hypokalemia (decreased potassium): May be seen in primary hyperaldosteronism, Cushing's syndrome, vomiting, diarrhea, and in patients on diuretics (potassium-losing) or with severe burns.

Clinical Utility

• The quantitation of potassium is used to monitor electrolyte balance.
• Pseudohyperkalemia: If an increase in platelets or leukocytes is suspected as a cause of hyperkalemia, a heparin tube should be obtained for plasma potassium.

CPT Codes

84132

Contacts

Last Updated

10/29/2023