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serum osmolal gap
Reference interval:
- < 10 mOsm/L
Principle:
1) calculated serum osmolality is given by the formula:
2[Na+] + glucose (mg/dL)/18 + BUN (mg/dL)/2.8
+ BAL* (mg/dL)/3.7) to exclude ethanol
* BAL = blood alcohol level
2) the osmolal gap is the difference between the measured vs calculated osmolality
3) it is important to obtain [Na+], [glucose] & [BUN] on the same specimen as the measured osmolality measured vs the calculated osmolality
Clinical significance:
- an increased osmolal gap may indicate a toxin
- a normal osmolal gap does not rule out all toxins
Increases:
1) ethanol
2) ethylene glycol
3) isopropanol
4) methanol
5) propylene glycol
6) glycerol
7) mannitol
8) sorbitol
9) acetone
10) diatrizoate
Related
serum osmolality
urine osmolal gap
General
general chemistry test
References
- Medical Knowledge Self Assessment Program (MKSAP) 16,
American College of Physicians, Philadelphia 2012