SERUM OSMOLAL GAP IN HEALTHY PERSONS: COMPARISON OF ELEVEN FORMULAS FOR CALCULATING OSMOLALITY
ABSTRACT: Serum osmolal gap,
the difference between measured and calculated osmolality, has been determined
on 64 healthy individuals (32 males and 32 females). The calculation of
calculated osmolality as well as osmolal gap utilized eleven formulas taken
from the literature. Measured osmolality was determined by osmometer. The
results showed that the mean ± SD of measured osmolality of males and females
were 283.50 ± 5.75 and 284.28 ± 3.66 respectively; however there was no
significant difference between males and females. Calculated osmolality was
determined by calculation using eleven formulas (formula A,B,C,D,E,F,G,H,I,J,
and K) utilization data of serum sodium,
potassium, glucose, and urea/ urea N. The osmolal gap of healthy males and
females was obtained as a difference between measured and calculated osmolality
determined by each formula. All the osmolal gaps obtained showed significant
difference between males and females except for the formula H. Using the
formula H, however, ,it was shown that the difference between males and females
and also the difference between measured and calculated osmolality (osmolal
gap) were not significantly different. In the present study it was concluded
that formula H (1.89Na + 1.38K + 0.03SUN + 1.08Glucose + 7.45) was the most
accurate formula for calculating calculated osmolality. The reference (normal) value
of osmolal gap was less than 13.4 mosmol/ kg H2O (males and females). The
author recommends using the formula H for calculating calculated osmolality as
well as osmolal gap for clinical purposes.
Author: SP Edijanto
Journal Code: jpkedokterangg050025
