  Detection efficiency loophole poses a significant problem for experimental
tests of Bell inequalities. Recently discovered Pusey-Barrett-Rudolph (PBR)
theorem suffers from the same vulnerability. In this paper we calculate the
critical detection efficiency, below which the PBR argument for the ontic
nature of quantum state is inconclusive. This is done for the maximally
$\psi$-epistemic models. We use two different definitions of this property. The
optimal number of parties, for which the critical detection efficiency is the
lowest is given. We also approach the problem from the opposite direction. We
provide a function which enables us to specify which epistemic models are ruled
out by the results of an experiment with a given detection efficiency.
