  We investigated the evolution of the primordial density perturbations
produced by inflation with thermal dissipation. A full relativistic analysis on
the evolution of initial perturbations from the warm inflation era to a
radiation-dominated universe has been developed. The emphasis is on tracking
the ratio between the adiabatic and the isocurvature mode of the initial
perturbations. This result is employed to calculate a testable factor: the
super-Hubble suppression of the power spectrum of the primordial perturbations.
We show that based on the warm inflation scenario, the super-Hubble suppression
factor, $s$, for an inflation with thermal dissipation is at least 0.5. This
prediction does not depend on the details of the model parameters. If $s$ is
larger than 0.5, it implies that the friction parameter $\Gamma$ is larger than
the Hubble expansion parameter $H$ during the inflation era.
