Flashcards in Lecture 29: Measuring Patients’ Experience Deck (17)

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1

##
Patient Reported Outcomes (PRO)

In certain cases, measuring health related quality of life is more appropriate than dichotomous outcomes regarding morbidity & mortality

give some examples?

when are they used?

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– E.g., Rheumatoid arthritis (pain, function)

– E.g., Upper Respiratory Tract Infections (symptoms, function)

– E.g., Migraine (pain)

– E.g., Depression (mood)

– When the goal is to improve how people are feeling

– When life prolonging treatments lead to deterioration of HRQOL (e.g.,

cancer chemotherapy)

– When the relationship between lab measurements and HRQOL is

uncertain

2

## 2 types of Instruments Used to Measure Patient Reported Outcomes

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generic

disease specific (see full list on slides)

3

##
what does St. George's Respiratory Questionnaire for

COPD (SGRQ-C) measure?

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• Measure of health status for patients with COPD

• 40 items

• Score range 0-100

• Higher scores indicate worse health status

4

## what are 2 measures of central tendency?

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– Mean

– Median

5

## what are 3 measures of spread?

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– Standard deviation

– Range

– Interquartile range

6

##
clinical trials involve measurement at _________ and then compare the mean differences

between groups.

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baseline and after treatment

Clinical trials may involve measurement of a continuous

outcome and then compare the mean scores between groups.

– Ignore the baseline data and just compare the mean post measurements

– Analyse the mean change in measurement from baseline to follow-up to

account for the influence of the baseline measurement

– Analyse the mean change in scores at follow-up whilst accounting for

baseline scores (achieved using a regression model, i.e., ANCOVA)

7

## see slides for NSAIDS ex

### ok

8

## Statistical vs. Clinical Significance

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• If something is statistically significant, it has no relevance to the clinical significance

– Very small differences that are not clinically meaningful may be statistically significant

• Statistical significance only means the results were unlikely due to random error

• Statistical Significance ≠ Clinical Significance

9

## why is it easier to show statistically significant differences in a continuous variable than a dichotomous one

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Why?

– Continuous variables are measured more “finely”

– It is easier to show differences in intervention and control on a scale

that has many points in comparison to one with rougher categories

(i.e., fewer points)

10

## 2 ways to interpret the results when the Units are Not Self Evident?

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– Anchor

– Distribution based approaches

11

##
Anchor Based Approach

explain

what is MCID?

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The anchor is an independent standard that is itself

interpretable and correlated to the instrument being explored

• Establish MCID (minimum clinical important difference)

– Smallest difference in score that patients perceive as beneficial and

would mandate an change in patients management

12

## what are typical anchors?

### • Typical anchor: no change, small change, moderate change, large change.

13

##
What do you Think is a Clinically Meaningful Improvement in SGRQ-C?

responder analysis:

**RATHER THAN LOOKING AT AVG CHANGE B/W GROUPS WE CANT AKE PROPORTION OF PPL THAT HAVE 4 PT CHANGE AND DEPICT THOSE NUMBERS AND COMPAR THE RESPONDERS IN YES NO DICHOTOMOUS WAY TO SEE IF THERE WAS A BENEFIT IN TREATMENT

Can talk about odds ratio, relative risk

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Score Range (0 to 100)

A. 1 point

B. 5 points

C. 10 points

D. 20 points

E. 50 points

F. More than 50 points

Minimal Clinically Important Difference (MCID)

• MCID = 4 points as compared with the score with placebo

14

## Distribution Based Approach

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Effect Size

• Aka Standardized Mean Difference

• Summary estimate of effect expressed in Standard Deviation units

15

## Standardized Mean Difference SMD equation

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SMD = Mean (intervention) – Mean (control)

_________________________

Standard Deviation of Scores Measured at Baseline

Interpretation:

16

## Interpretation of SMD values

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– 0.5 means that the mean effect is half of an SD unit.

– Rule of Thumb: 0.2 Small Effect, 0.5 Moderate Effect, 0.8 Large Effect

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