If you are "invited" to claim PIP then any DLA award you had is now irrelevant. It does not matter what level of DLA award you had or for how long, lifetime awards are gone. PIP is a whole new ball game and the criteria are very different to DLA. Forget about what you had, the slate is wiped clean. You now have to provide evidence to support how your condition affects the things you can do not what your conditions are. PIP is a test of functionality, not a medical examination. You will only score points and get the award you deserve by proving how your condition affects what you can do, either on your own, with the use of aids or with more help from other people.
