Troubleshooting Erroneous Potassiums in a Clinical Laboratory Setting

Potassium (K⁺) is one of the most commonly analyzed elements in the chemistry laboratory. It can be ordered by a physician as a single test, or it can be run as part of an electrolyte panel, and analyzed in conjunction with sodium, chloride and CO₂. In the human body, potassium plays important roles in maintaining water balance and distribution, acid-base balance, muscle and nerve cell function, and heart, kidney and adrenal function.

The normal range for serum potassium is 3.5-5.0 mEq/L. When a patient exhibits a low potassium (hypokalemia), it can lead to muscle weakness, irritability, paralysis, and at very low levels, cardiac arrest. Conversely, elevated potassium (hyperkalemia), can be seen in patients with dehydration, diabetic ketoacidosis, severe burns and renal failure. Hyperkalemia is associated with mental confusion, muscle weakness, electrocardiographic changes, with peripheral vascular collapse and cardiac arrest if levels exceed 7.0 mEq/L.

It is important for the laboratory to report an accurate potassium result to the physician for proper patient treatment and management. It is, therefore, necessary to be aware of the many preanalytical variables that can contribute to erroneous potassium values. These include patient factors, venipuncture technique and specimen handling and processing variables.

An erroneous result can be due to one preanalytical variable, or it can be a cumulative effect of several variables.

The Potassium Chart in this issue of LabNotes will assist you in troubleshooting elevated potassium results. The wall chart is broken down into three sections (specimen collection, processing/handling/transport, and physiological issues) and gives possible causes and corrective actions to use when trying to remedy an erroneous K⁺ value.

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