Osmolality, Serum
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.
New York Approved
Methodology
Automated Analyzer (Clinical Chemistry)
Biomarkers
LOINC Codes
- 2692-2
- 2692-2
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2 mL
Minimum Volume
0.25 mL
Container
Plastic vial
Collection Instructions
Centrifuge and aliquot serum into a plastic vial.
Causes for Rejection
N/A
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 24 hours |
| Refrigerated | 7 days |
| Frozen | 7 days |