Normal Osmolal Gap (measured serum Osm – calculated serum Osm):
Normal gap: 15-20
Elevated osmolal gap indicates presence of a low MW solute (acetone/ETOH/ethylene glycol/isopropanol/MeOH) or unmeasured electrolyte (Mg) or sugar (mannitol/sorbitol/glycine)
Measured Serum Osm = from laboratory
Calculated Serum Osm = (2 x Na) + (glucose/18) + (BUN/2.8)
BUN: normal
Acetest/Ketostix (Nitroprusside reaction only detects acetoacetic acid):
When a nitroprusside reaction test is used, paraldehyde may cause a false-positive reaction for ketones, called “pseudoketosis”
Acetaldehyde can be found in the urine and blood, but many laboratories do not automatically test for this
