Osmolality, Serum

Casandra

Casandra Test Code MC63431Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID UOSMSCPT Code 83930

Clinical Use

Use

This test is useful for evaluating acutely ill or comatose patients. Osmolality is a measure of the number of dissolved solute particles in a solution. It is not affected by the type of particles in solution but rather by their quantity. Changes in osmolality can affect the physical properties of biological solutions, such as osmotic pressure and freezing point. Serum osmolality levels are indicators of hydration status and can guide fluid replacement therapy, as an increase suggests dehydration and a decrease suggests overhydration. Carefully monitored in patients receiving intravenous fluids to maintain balanced electrolyte and water administration.

Special Instructions

The test requires serum to be collected, preferably in a red-top tube, though a serum gel tube is acceptable. After centrifugation, the serum should be aliquoted into a plastic vial. Testing is continuous, performed every day from Monday through Sunday, with results typically available within 1 day. The reference range is 275-295 mOsm/kg.

Limitations

This test has no significant cautionary statements regarding improper specimen collection or handling, test selection, or interfering substances. The ratio of serum sodium to serum osmolality might be distorted in cases of drug intoxication. It's essential to calculate and compare the measured and calculated serum osmolality for thorough interpretation, especially for assessing the prognosis in critically ill patients with a delta-osmolality above 40 mOsm/kg H2O.

Test Details

New York Approved