Lab Test

Potassium, Serum

K

Test Codes

Antrim #15770, EPIC: LAB5101, SOFT: K

Instructions

Note: 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

FOR EC AND INPATIENT SAMPLE COLLECTION ONLY:

Preferred Sample:  One Light Green Top Plasma Separator Tube (PST)(Minimum Whole Blood: 4.0 mL)

Acceptable Sample:  One Gold Top SST (Minimum Whole Blood:  4.0 mL)

FOR PHYSICIAN OFFICE/OUTREACH SAMPLE COLLECTION:

COLLECT:  One Gold Top SST (Minimum Whole Blood:  4.0 mL) 

Contact Laboratory for acceptability of other tube types.
See Minimum Pediatric Specimen Requirements for Microtainer® collection.

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

Physician Office/Draw Specimen Preparation

Let SST specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged SST tube within two hours of collection. (Minimum: 0.5 mL)

Preparation for Courier Transport

Transport: Centrifuged SST tube, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL)

Rejection Criteria

  • Moderate to grossly hemolyzed specimens.
  • Inadequately centrifuged Microtainers® or Gold-top tubes.
  • Red-top tubes with serum not separated from cells within two hours of collection.

In-Lab Processing

Let SST specimens clot 30-60 minutes. Centrifuge SST tubes or Microtainers® to separate serum from cells. Deliver immediately to the appropriate testing station.


Storage

Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers® with Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers® without Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

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

Specimen Storage in Department Prior to Disposal:

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

Laboratory

Farmington Hills Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory
Troy Chemistry Laboratory

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


Breast Milk
(15 days to 15 months post partum): 8.7-17.5 mmol/L.

Test Methodology

Potentiometric.

Interpretation

  • Spuriously increased levels may be seen:
    • Following excessive hand clenching prior to phlebotomy.
    • If the needle (or Vacutainer®) has been inserted into an EDTA tube prior to the tube used for potassium analysis.
    • If whole blood sample is refrigerated prior to separation of serum from red cells.
    • In a hemolyzed sample.
    • 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

11/9/2020

Microtainer® and Vacutainer® are registered trademarks of Becton, Dickinson and Company.
UroVysion® is a registered trademark of Abbott Laboratories. ThinPrep® is a registered trademark of Hologic, Incorporated.

 

This directory currently reflects information only for specimens collected and/or processed at the
Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.