Evidence-appraisal glossary
Minimal clinically important difference
The minimal clinically important difference (MCID) is the smallest change in an outcome that patients or clinicians would regard as meaningful, rather than merely detectable.
Also called: MCID, minimal important difference, minimum clinically important difference.
The MCID gives a yardstick for judging whether a statistically significant result actually matters, since a drug can lower a symptom score by an amount that is real but too small to notice. It is often estimated from patient-reported anchors or expert consensus, so different studies may use different thresholds for the same scale. A confidence interval that sits entirely below the MCID suggests an effect too small to be worthwhile, even when the p-value is small.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.