Levels of Evidence (Qualitative, Modified Best-Evidence Synthesis)

Level I – Strong evidence
Multiple high-quality randomized controlled trials (RCTs) and/or consistent meta-analyses with low bias.

Level II – Moderate evidence
At least one high-quality RCT or multiple moderate-quality RCTs with consistent findings.

Level III – Limited-moderate evidence
One moderate-quality RCT and/or multiple high-quality observational studies with consistent results.

Level IV – Limited evidence
Observational studies, single-arm studies, case series, or inconsistent RCT data.

Level V – Consensus / expert opinion
Expert opinion, narrative reviews, or mechanistic rationale without controlled clinical data.