Stringent Tests of CPT Invariance 
C = charge conjugation (changing a particle into its antiparticle)
P = party transformation (r → r)
T = time reversal transformation (motion reversal)
CPT is the application of all of these symmetry operations.
The CPT theorem, one of the most basic assertions of physics, arises from the success of quantum field theories. Quantum field theories seem to provide a very successful description of all interactions except for gravitational interactions. Where a quantum field theory is a correct description, along with the usual assumptions such as invariance under Lorentz transformations, the necessary result is that the reality that is described is invariant under a CPT transformation. This is called the CPT theorem. However, since gravity has not yet been successfully described by a quantum field theory, it is possible that the CPT is not universal. The only way to tell is to look.
CPT invariance implies that particles and antiparticles have the same:

A simple explanation of CPT invariance is in a popular account of our low energy antiproton methods and Q/M measurements.

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