  We examine the latest HERA experimental measurements of the $Q^2$ logarithmic
derivative of the proton structure function. We analyze the characteristics of
DGLAP with and without screening, as well as a Regge type model, and compare
their predictions to all available data on $\slope$ including those for fixed
W. Our results show that the present data can be described in pQCD taking into
account shadowing corrections. However, such a description cannot be considered
a conclusive signal of gluon saturation since the experimental data on $\slope$
do not allow one to discriminate between the various approaches, in spite of
their very different construction.
