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Alternative names, keywords |
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Samples required |
● Clotted blood (gold cap, 5 mL tube). Smaller tubes are available for paediatric samples. |
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Test indications |
Serum osmolality can be estimated as 2x[sodium] + [urea] + [glucose] or 2x([sodium] +[potassium]) + [urea] + [glucose] (there are several variations of this calculation in use. All results in mmol/L) Caution if other solutes are present in concentrations > 5mmol/L (see osmolal gap below), or if pseudohyponatraemia present due to high serum protein or lipaemia. Osmolal gap A measured osmolality >10 mOsmol/kg higher than calculated suggests the presence of other osmotically active solutes e.g. ethanol, methanol, ethylene glycol, mannitol. Source: UpToDate Serum Osmolal Gap, last updated: Sep 16, 2020 |
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Factors affecting test performance/ results |
See above. |
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Reference range |
275 - 295 mOsmol/kg Source: Agreed Clinical Biochemistry Reference Intervals, Pathology Harmonisation of Reference Intervals, Pathology Harmony Group 2011 |
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Turnaround time |
24 hours From 16/06/26, osmolality will only be processed between 09:00 - 17:30 Monday - Sunday. Out of hours analysis not available. |
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Enquiries |
Biochemistry (Automation) |