  We show that the Reshetikhin-Turaev-Walker invariant of 3-manifolds can be
normalized to obtain an invariant of 4-dimensional thickenings of 2-complexes.
Moreover when the underlying semisimple tortile category comes from the
representations of a quantum group at a primitive prime root of unity, the
0-term in the Ohtsuki expansion of this invariant depends only on the spine and
is the mod p invariant of 2-complexes defined previously from the second
author. As a consequence it is shown that when the Euler characteristic is
greater or equal to 1, the 2-complex invariant depends only on homology. The
last statement doesn't hold for the negative Euler characteristic case.
