Blog Post

MCIDs: What Are They, and Why Do They Matter?

Minimal clinically important differences can play a major role in keeping patients engaged with treatment—and adjusting plans of care.

Kylie McKee
5 min read
July 7, 2023
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Things aren’t always as they appear, and that’s certainly true when it comes to measuring the success of rehab therapy treatment. As any therapist knows, if you make decisions based on observational data alone, determining whether or not your treatment is making a difference can prove difficult. That’s why outcomes exist: they give therapists an objective, concrete way to measure patient improvement. But, a positive patient-reported outcome score isn’t necessarily enough to tell you that your treatment is effective. That’s where minimal clinically important differences (MCIDs) emerge.

What are minimal clinically important differences? 

Tracking Patient Improvement

MCIDs are research values that are crucial to determining the efficacy and effect size of any given treatment modality or plan. In terms of therapy outcomes, MCIDs represent the minimum change of statistical significance to the outcomes score in the domain of interest patients should experience in order for them, their providers, or other overseeing bodies to confirm that therapy is creating a positive difference.

Here are the MCIDs for a few common outcome measurement tools in rehab therapy:

For example: Let’s say you’re treating a patient for chronic neck pain. You might use the Neck Disability Index to measure the patient’s initial level of disability and track his or her progress. Let’s also say that the patient began therapy with an NDI score of 33—which denotes “severe disability.” But over time, the patient’s score decreases to 26. In this scenario, 26 is still considered “severe disability”; however, the seven-point drop indicates a meaningful, objective, and measurable change, because it exceeds the MCID for the Neck Disability Index (which is a decrease of five points).

Anchor-Based Method vs. Distribution-Based Method

Diving further into the weeds on MCIDs, there are two different methods of determining a minimal clinically important difference: anchor-based methods and distribution-based methods. As this study on the two approaches explains, an anchor-based method “compares the change in a scale-based outcome measure with that of a patient-reported outcome (e.g., global ratings of change) or other external criterion.” On the other hand, a distribution-based approach “compares the difference in a scale-based outcome measure to a pre-specified threshold value of its uncertainty (e.g., standard error, standard deviation [SD]), which facilitates MCID derivation when direct patient or clinician input is not readily accessible.” 

Why are minimal clinically important differences important?

Preventing Patient Dropout

Let’s face it: physical therapy isn’t exactly a cakewalk for many patients. Sometimes, it can feel like an uphill battle, particularly if a patient doesn’t notice any significant improvement in their quality of life. When this happens, patients might disappear from therapy before they’ve completed treatment. However, if patients are meeting the MCIDs for applicable outcome measures, you can have an honest conversation explaining how therapy is actually working—even if treatment isn’t something patients perceive as beneficial yet.

Updating Treatment Plans

While MCIDs can be instrumental in demonstrating the efficacy of therapy to patients, they can also play a crucial role in helping providers identify points along the course of care at which a patient’s treatment plan is in need of adjustment. As a provider, you can catch ineffective—or even contradictory—interventions by assessing the patient’s progress at regular intervals and comparing his or her outcomes to the applicable MCIDs.

You can’t always take things at face value. Just because you don’t observe a major change from week to week during the course of therapy treatment, it doesn’t mean improvement is non-existent. That’s why tracking outcomes is crucial to delivering meaningful results through evidence-based treatment interventions and modalities. By using MCIDs and outcomes in tandem, you can ensure that you’re delivering the best possible care to every patient—every time.


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