  We investigate the effect of observational constraints such as
signal-to-noise, resolution and column density level on the HI morphological
asymmetry ($\mathrm{A}_\mathrm{mod}$) and the effect of noise on the HI global
profile ($\mathrm{A}_\mathrm{flux}$) asymmetry indices. Using mock galaxies
from the EAGLE simulations we find an optimal combination of the observational
constraints that are required for robust measurement of the
$\mathrm{A}_\mathrm{mod}$ value of a galaxy: a column density threshold of
$5\times10^{19}cm^{-2}$ or lower at a minimal signal-to-noise of 3 and a galaxy
resolved with at least 11 beams. We also use mock galaxies to investigate the
effect of noise on the $\mathrm{A}_\mathrm{flux}$ values and conclude that a
global profile with signal-to-noise ratio greater than 5.5 is required to
achieve a robust measurement of asymmetry. We investigate the relation between
$\mathrm{A}_\mathrm{mod}$ and $\mathrm{A}_\mathrm{flux}$ indices and find them
to be uncorrelated which implies that $\mathrm{A}_\mathrm{flux}$ values cannot
be used to predict morphological asymmetries in galaxies.
