  Quark number susceptibilities at finite quark chemical potential are
investigated in the framework of the Polyakov-loop-extended Nambu Jona-Lasinio
(PNJL) model. A detailed comparison is performed between the available lattice
data, extrapolated using a Taylor expansion around vanishing chemical
potential, and PNJL results consistently obtained from a Taylor series
truncated at the same order. The validity of the Taylor expansion is then
examined through a comparison between the full and truncated PNJL model
calculations.
