Calculates expected serum osmolarity, for comparison to measured osmolarity to detect unmeasured compounds in the serum.
To detect unmeasured compounds in the serum. Osmolal gaps (difference between measured and expected) of >10 can be caused by toxic alcohols.
Formula 1 Purssell et al equation for calculating serum osmolality with US units: Serum osm [mOsm/kg] = (2 × Na + (BUN / 2.8) + (glucose / 18) + (ethanol / 3.7) Purssell et al equation for calculating serum osmolality with SI units: Serum osm [mOsm/kg] = 2 × Na + BUN + glucose + ethanol Normal serum osm is 285-295 Formula 2 Osmolal gap equation: Osmolal gap [mOsm/kg] = measured serum osm [mOsm/kg or mmol/kg] - calculated serum osm [mOsm/kg] Normal serum osm gap is -14 to +10
1. Purssell RA, Pudek M, Brubacher J, Abu-Laban RB.Derivation and validation of a formula to calculate the contribution of ethanol to the osmolal gap.Ann Emerg Med 2001;38(6): 653-9.doi:10.1067/mem.2001.119455. PMID 1171974. 2. Glasser L, Sternglanz PD, Combie J, Robinson A. Serum osmolality and its applicability to drug overdose. Am J Clin Pathol. 1973 Nov;60(5):695-9. doi: 10.1093/ajcp/60.5.695. PMID: 4751712.
OBSERVATION.lab_test-serum_sodium.v1, OBSERVATION.lab_test_glucose.v1, OBSERVATION.lab_test_serum_ethanol.v0, OBSERVATION.lab_test-urea_and_electrolytes.v1, OBSERVATION.blood_serum.v0