Evidence Scope
These research surveys include evidence ranging from established human data to preclinical research and biological extrapolation. The language used is intended to reflect the strength of that evidence.
Speculative — A biological hypothesis with limited direct supporting evidence. The proposed mechanism or effect is scientifically conceivable but substantially uncertain.
Plausible / Possible — Supported by relevant preclinical, mechanistic, or limited human evidence. The extrapolation is biologically reasonable, but the proposed effect has not been demonstrated with enough evidence to consider it probable.
Likely / Probable — Supported by stronger and reasonably consistent evidence suggesting the effect is more likely than not, although uncertainty remains.
No qualification — Used when the statement is sufficiently well established by the available evidence, e.g. large scale human trials.
Mechanistic evidence is not treated as equivalent to clinical evidence, but i is also not dismissed simply because large human trials are unavailable. A mechanistically supported extrapolation is appropriate when the underlying biology is credible and the strength of the language matches the evidence.
For combinations, complementary mechanisms may justify describing an additive or synergistic effect as possible or plausible, but not as established unless the combination itself has been tested together.