MCID, MIC, MDC, and PASS Are Four Different Questions, Not Four Names for the Same Threshold

Four questions wearing one word: "threshold"

Jaeschke, Singer, and Guyatt defined the MCID in 1989 as the smallest change in a score that a patient would perceive as beneficial, small enough that it's still worth continuing a treatment absent excessive cost or side effects.¹ The MIC is close enough to this that the two terms are frequently, and confusingly, used as if they were the same thing. Terwee and colleagues' 2021 clarification defines the MIC specifically as a threshold for the smallest within-person change over time above which a patient perceives themselves as importantly changed, and their paper opens by naming the exact problem this creates: so much confusion exists between MIC and MDC as concepts that it calls into question the validity of published values for either one.² A 2011 critique goes further, cataloguing half a dozen near-synonymous terms in circulation for what is, in most papers, roughly the same idea applied slightly differently by different research groups.³

The MDC is a different kind of number entirely, built from test-retest reliability rather than from anyone's opinion about what matters. It answers whether an observed change is bigger than the noise the instrument produces on repeated administration to a patient whose true condition hasn't changed.⁴ None of MCID, MIC, or MDC ask about a patient's current state in isolation, only about the size of a change.

PASS breaks that pattern completely. Defined by Tubach and colleagues in 2005, PASS asks a single question with no reference to a starting point at all: given where the patient's score sits right now, would they consider that state acceptable.⁵ A patient can clear the MCID with a large, clinically important improvement and still not reach PASS, if their baseline was severe enough that even a meaningful gain leaves them somewhere they wouldn't call acceptable. The reverse also holds: a patient who started only mildly affected might already be in an acceptable state with very little change at all.

One dataset, four numbers

A 2024 study established the MCID, MIC, MDC, and PASS of the Oxford Shoulder Score in the same 100 patients following shoulder arthroplasty, using patient satisfaction ratings as the anchor and a distribution-based method for the MDC.⁶

Two things are worth sitting with in that table. First, the MCID (6.9) and MDC (6.6) are close enough here that the authors could conclude a clinically important change on this instrument is also large enough to trust as real, which is not guaranteed and doesn't hold for every instrument.⁶ Second, and more fundamentally, PASS isn't measured in the same units as the other three at all. It's not a change score with a confidence interval around it; it's a fixed point on the scale itself. Reporting "the mean improvement exceeded the MCID" and "78% of patients reached PASS" in the same results section is not redundant. They are answers to two different questions a patient might reasonably ask: did I get better, and am I okay now.

All four of these values are specific to the instrument, the population, and the follow-up interval in which they were established. An MCID of 6.9 for the Oxford Shoulder Score after shoulder arthroplasty says nothing about its MCID after a different procedure, and the same caveat applies to MIC, MDC, and PASS individually. Match the source population to your own before citing any of the four.

What this changes in a results section

Match the threshold to the question you're actually asking, rather than defaulting to MCID because it's the most familiar term. If the question is whether a change was big enough to matter, report the MCID or MIC, whichever your source population most resembles, and say which one you used since the terms are not interchangeable even when a paper treats them as such. If the question is whether that change is distinguishable from measurement noise, that's the MDC. If the question is whether patients ended up somewhere they'd call acceptable, independent of how far they had to travel to get there, that's PASS, and it needs to be reported as a proportion of patients crossing an absolute cut point, not folded into a change-score narrative where it doesn't belong.

Frequently asked questions

What is the difference between MCID and PASS?

MCID measures whether the size of a change from baseline matters to a patient. PASS (patient-acceptable symptom state) ignores baseline entirely and asks whether the patient's current score, regardless of how they got there, is one they'd consider acceptable.

Are MCID and MIC the same thing?

They are frequently used interchangeably, but the terms are methodologically distinct and the confusion between them is significant enough that it calls into question the validity of some published values for both.

Can a patient clear the MCID without reaching PASS?

Yes. A patient can experience a large, clinically important improvement and still not reach an acceptable symptom state if their starting point was severe enough that even a meaningful gain leaves them below that threshold.

References

1. Jaeschke R, Singer J, Guyatt GH. Measurement of health status. Ascertaining the minimal clinically important difference. Controlled Clinical Trials. 1989;10(4):407–415. https://doi.org/10.1016/0197-2456(89)90005-6
2. Terwee CB, Peipert JD, Chapman R, Lai JS, Terluin B, Cella D, Griffiths P, Mokkink LB. Minimal important change (MIC): a conceptual clarification and systematic review of MIC estimates of PROMIS measures. Quality of Life Research. 2021;30(10):2729–2754. https://doi.org/10.1007/s11136-021-02925-y
3. King MT. A point of minimal important difference (MID): a critique of terminology and methods. Expert Review of Pharmacoeconomics & Outcomes Research. 2011;11(2):171–184.
4. Beckerman H, Roebroeck ME, Lankhorst GJ, Becher JG, Bezemer PD, Verbeek ALM. Smallest real difference, a link between reproducibility and responsiveness. Quality of Life Research. 2001;10(7):571–578. https://doi.org/10.1023/A:1013138911638
5. Tubach F, Ravaud P, Baron G, Falissard B, Logeart I, Bellamy N, Bombardier C, Felson D, Hochberg M, van der Heijde D, Dougados M. Evaluation of clinically relevant states in patient reported outcomes in knee and hip osteoarthritis: the patient acceptable symptom state. Annals of the Rheumatic Diseases. 2005;64(1):34–37. https://doi.org/10.1136/ard.2004.023028
6. Liu P, Afzal I, Asopa V, Clement ND, Patel V. Changes and thresholds in the Oxford Shoulder Score following shoulder arthroplasty: minimal clinically important difference, minimal important and detectable changes, and patient-acceptable symptom state. Shoulder & Elbow. 2024. https://doi.org/10.1177/17585732231176423