  Let $\Omega\subset\mathbb{C}^n$ be a bounded pseudoconvex domain. We define
the Diederich-Forn{\ae}ss index with respect to a family of functions to be the
supremum over the set of all exponents $0<\eta<1$ such that there exists a
function $\rho_\eta$ in this family such that $-\rho_\eta$ is comparable to the
distance to the boundary of $\Omega$ on $\Omega$ and such that
$-(-\rho_\eta)^\eta$ is plurisubharmonic on $\Omega$. We first prove that
computing the Diederich-Forn{\ae}ss index with respect to the family of upper
semi-continuous functions is the same as computing the Diederich-Forn{\ae}ss
index with respect to the family of Lipschitz functions. When the boundary of
$\Omega$ is $C^k$, $k\geq 2$, we prove that the Diederich-Forn{\ae}ss index
with respect to the family of $C^k$ functions is the same as the
Diederich-Forn{\ae}ss index with respect to the family of $C^2$ functions.
