Evidence grade

Evidence grade is a rating attached to a clinical claim describing how confident the research actually supports it, distinct from whether the claim is true or false: a claim can be well-supported by strong evidence and still turn out to be revised later as more research accumulates, and a claim can turn out to be correct despite currently resting on limited evidence.

In The Research Says series, a claim earns a strong grade when it's backed by multiple systematic reviews or large, well-designed trials that agree with each other; moderate when the evidence points a clear direction but comes from fewer or smaller studies, or from studies with some real limitations; and limited when the available research is thin, mixed, or mostly based on weaker study designs, meaning the honest, current answer is closer to "probably" than to "definitely."

Reading the evidence grade alongside the claim itself, rather than treating every conclusion in a research summary as equally certain, is what separates using research well from simply citing it: a strong-graded finding is worth building a protocol around, while a limited-graded one is worth watching rather than acting on as if it were settled.