Minimal Clinically Important Differences MCID

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Minimal Clinically Important Differences (MCID)
Robert M. Kaplan (some slides from Ron
Hays) February 13, 2006
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Responsiveness to Change

• HRQOL measures should be responsive to
• interventions that change HRQOL
• Evaluating responsiveness requires assessing
• HRQOL relative to an external indicator of
  change (anchor)

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Two Essential Elements

• 1. External (not HRQOL measure being evaluated)
  indicator of change (Anchor)
• 2. Amount of HRQOL change among those determined
  to have changed on anchor, relative to noise
  (variance).

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Kinds of Anchors

• Self-report
• Clinician or other report
• Clinical parameter
• Clinical intervention

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Self-Report Anchor (A)

• Overall has there been any change in your asthma
  since the beginning of the study?
• Much improved Moderately improved Minimally
  improved
• No change
• Much worse Moderately worse Minimally worse

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Examples of Other Anchors

• Clinician report
• How is Jans physical health now compared to 4
  weeks ago?
• Clinical parameter
• Change from CDC Stage A to B
• Became seizure free
• Clinical intervention
• Before and after Prozac

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Change and Responsiveness in PCS Depends on
Treatment
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Change and Responsiveness in MCS Depends on
Treatment
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Magnitude of HRQOL Change Should Parallel
Underlying Change
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Minimal Important Difference (MID)
Some differences between groups or over time may
be so small in magnitude that they are not
important. Smallest difference in score that is
worth caring about (important). Change large
enough for a clinician to base treatment
decisions upon it.
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Two Essential Elements
1. Indicator (not HRQOL measure being evaluated)
of minimal change (Anchor) 2. Amount of HRQOL
change among those determined to have changed on
anchor.
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Example Anchor (1)
People who report a minimal change How is
your physical health now compared to 4 weeks ago?
Much improved Moderately Improved
Minimally Improved No Change Minimally
Worse Moderately Worse Much Worse
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MID Varies by Anchor

• 693 RA clinical trial participants evaluated at
  baseline and 6-weeks post-treatment.
• Five anchors 1) patient global self-report 2)
  physician global report 3) pain self-report 4)
  joint swelling 5) joint tenderness
• Kosinski, M. et al. (2000). Determining
  minimally important changes in generic and
  disease-specific health-related quality of life
  questionnaires in clinical trials of rheumatoid
  arthritis. Arthritis and Rheumatism, 43,
  1478-1487.

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Changes in SF-36 Scores Associatedwith Minimal
Change in Anchors
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Samsa et al. (1999, p. 149) said

• MID for SF-36 is typically in the range of 3 to
  5 points (p. 149). .09-gt0.28 ES
• Samsa, G., Edelman, D., Rothman, M. L., Williams,
  G. R., Lipscomb, J., Matchar, D.
  Pharmacoeconomics, 15, 141-155 1999.

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MID Determination Complicated By Cumulative
Change Over time

Baseline 42 Year 4 36 Note 4-year decline in
PCS among US seniors, 1990-94. -gt 1.5 points
per year (0.15 SD)

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MID Varies by Starting Position

• Same retrospective report of change associated
  with bigger prospective change for those with
  more room to change
• Among those who said their physical health was
  somewhat worse, change ranged from 26 points to
  3 points for people with high (81-100) versus
  low (0-20) baseline physical health (Baker et
  al., 1997, Medical Care).

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Group Average is Different from Individual Change

• Average change collapses across individual
  responses.
• Is inference about minimum amount of change that
  is important for individuals based on a group
  average reasonable?
• What if scale score improved by 4 points for half
  the people and 0 points for the other half? Is
  the MID 2 or 4?

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Example Use of Self-Report Anchor in COPD

• Compared to Jack, my ability to walk is
• Much better Somewhat better A little bit
  better About the same A little bit worse
  Somewhat worse Much worse
• Determined how much actual walking distance had
  to differ, on average, for patients to rate
  themselves as walking either a little bit better
  or a little bit worse.
• Redelmeier, D. A. et al., 1997, Am J Respir Crit
  Care Med

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Example with Multiple Anchors

• 693 RA clinical trial participants evaluated at
  baseline and 6-weeks post-treatment.
• Five anchors
• 1) patient global self-report
• 2) physician global report
• 3) pain self-report
• 4) joint swelling
• 5) joint tenderness
• Kosinski, M. et al. (2000). Determining
  minimally important changes in generic and
  disease-specific health-related quality of life
  questionnaires in clinical trials of rheumatoid
  arthritis. Arthritis and Rheumatism, 43,
  1478-1487.

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Patient and Physician global reports

• How the patient is doing, considering all the
  ways that RA affects him/here?
• Very good (asymptomatic and no limitation of
  normal activities)
• Good (mild symptoms and no limitation of normal
  activities)
• Fair (moderate symptoms and limitation of normal
  activities)
• Poor (severe symptoms and inability to carry out
  most normal activities)
• Very poor (very severe symptoms that are
  intolerable and inability to carry out normal
  activities)

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Pain self-report

• 10 centimeter visual analog scale
• 0 no pain, 10 severe pain

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Threshold on Self-Report and Physician Report
Anchors Used for MID estimation

• Patient and physician global reports
• Improvement of 1 level over time.
• Pain self-report
• Improvement of 1-20 over time.

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Joint swelling and tenderness anchors

• Number of swollen and tender joints
• Threshold for MID estimation 1-20 improvement
  over time

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Recommendations

• Use multiple anchors
• Use anchors that represent minimal change
• Report average across anchors and studies, range,
  and SD
• Consider that it can be easier to conclude that a
  difference is clearly or obviously important than
  it is to say one is always unimportant (grey
  area).

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Appendix Terminology

• Minimally Important Difference (MID)
• Minimal difference (MD)
• Minimally Detectable Difference (MDD)
• Clinically Important Difference (CID)

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Value Depends on Cost

• A small positive change has greater value if it
  costs less.
• Importance of HRQOL change depends on what it
  costs to produce it.

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Summary
Identification of MID aids interpretation by
providing familiar anchors to unfamiliar
units. Trying to give a single point estimate is
too simplistic. Bounded estimates are necessary
given the uncertainty.
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So How Big Are Different Changes?

• Effect size benchmarks
• Small 0.20-gt0.49
• Moderate 0.50-gt0.79
• Large 0.80 or above

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(No Transcript)
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Example of Preference Approach

• National Emphysema Treatment Trial (NETT)

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Subjects

• 606 male and 387 female participants in the
  National Emphysema Treatment Trial (NETT)

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Exclusion Criteria

• characteristics that place them at high risk for
  peri-operative morbidity and/or mortality
• emphysema felt to be unsuitable for LVRS, and
• medical conditions or other circumstances that
  make it likely that the patient would be unable
  to complete the trial.

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Measures Pre-post rehabilitation, 12 months, 24
months

• Quality of Well being scale (QWB-SA)
• Medical Outcomes Study 36 Item Short Form (SF36)
• St. Georges Respiratory Questionnaire (SGRQ)
• UCSD Shortness of Breath Questionnaire (SOBQ).

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NETT Survival Result NEJM May 22, 2003
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NETT

• Patients were randomly assigned to
• maximal medical therapy
• LVRS. Those assigned to LVRS
• video assisted thoracoscopy (VATS
• median sternotomy

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Descriptive Statistics for Change Scores in
Rehabilitation Phase of NETT
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Change in QOL Measures by QWB change category
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Change in SOBQ by QWB Catetory
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Change in SGRQ by QWB Category
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Change in SF-36 PCS by QWB Category
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Change in SF-36 MCS by QWB Category
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Cumulative Mean QALYs Per Person
Years after year 1 discounted at 3 per
year Number alive at end of observation period
NETT
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(No Transcript)
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Comparison of Cost/QALY for Different Programs
in COPD (2002 dollars)
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Conclusions

• The preference scaling system in generic utility
  based quality of life measures provides a metric
  that is directly interpretable and avoids many of
  the criticisms of MCID measures
• Quality adjusted life years offer a valuable
  metric for policy analysis.
• Utility-based measures of health-quality of life
  should gain greater use in COPD outcomes
  research.