Introduction to outcome measures for physiotherapy students

1. Introduction to
Outcome Measures
Dr Sreeraj S R

2. Sreeraj S R
What are Outcome measures?
• Outcome measures are standardized tests, measures, or
instruments used to measure various aspects of a patient’s health
status.
• Results from outcome measures can be used for patient care
decisions, research, and quality assurance.
• An evidence-based practitioner must consider the dimension, type,
format, reliability, validity, responsiveness, and feasibility an
appropriate outcome measure for their patient.
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O’Sullivan.

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Broad Classification
• Disease specific: Tend to measure more specific elements of
the respective disease and are thus, theoretically, more
sensitive to subtle treatment-related changes.
• Example: the Western Ontario and McMaster University
Osteoarthritis Index (WOMAC) in OA patient.
• Generic: Typically assess the physical, social, and emotional
dimensions of health and they tend to have the advantage of
evaluating QOL for different type of diseases.
• Example: Short Form-36 (SF-36), which generates a profile
of eight dimensions in OA patient.
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Dimension
• Outcome measures may be multiple dimensional or focused.
• An example for a multidimensional stakeholder-focussed evaluation
approach is the “Tripartite Model of Mental Health and Therapeutic
Outcomes which differentiates between the perspectives of (a) society,
(b) the individual patient, and (c) the mental health professional.
• Region specific (e.g., Lower Extremity Functional Scale, Upper Extremity
Functional Scale ),
• Disease, or condition specific (e.g., Western Ontario and McMaster
Universities Arthritis Index),
• Patient specific (e.g., Patient Specific Functional Scale),
• Global (e.g., Global Rating of Change).
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O’Sullivan, Outcome Measures [Internet]. Physiopedia.

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Format
Outcome measures that we use in clinical practice are divided
into four categories:
1. Self-report measures
2. Performance-based measures
3. Observer-reported measures
4. Clinician-reported measures
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Outcome Measures [Internet]. Physiopedia.

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Self-report measures
• Patients respond verbally or in writing about their self-perception of
some aspect of their health status.
• Patient-reported outcome measures (PROMs) are questionnaires
measuring the patients’ views of their health status.
• Example: Health-related quality of life (HRQL)
• Patient-reported experience measures (PREMs) are
questionnaires measuring the patients’ perceptions of their
experience whilst receiving care.
• Example: CARE (Consultation and Relational Empathy) measure
questionnaire.
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Performance-based measures (PerfO)
• These require patients to perform a task that is graded by the
physical therapist.
• Scores for performance-based measures can be based on
either an objective measurement or a qualitative assessment
that is assigned a score.
• Example: Functional Independence Measure, which
requires the patient to demonstrate self-care activities,
transfers, locomotion, and bowel and bladder function.
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Clinical Outcome Assessment [Internet]. Physiopedia. 2020

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Observer-reported measures (ObsRO)
• Measurement based on an observation by someone other than the
patient or a health professional.
• Usually done by patient's non-clinical care giver, family or anyone
living around patient and observes the patient in daily life.
• Example: assessment of a patient's cognition.
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Clinical Outcome Assessment [Internet]. Physiopedia. 2020

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Clinician-reported outcome measures
(ClinRO)
• These are measurements that are completed by a health care
professional.
• Based on the report that comes from a trained health care
professional after observation of a patient's condition.
• Example: pain rating scale.
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Clinical Outcome Assessment [Internet]. Physiopedia. 2020

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Reliability
• The reliability of an outcome measure refers to its consistency or reproducibility.
• As the reliability increases, the amount of error inherent in the measurement
decreases.
• Different types of reliability that affect outcome measures;
• Test-retest refers to the stability of measurements over time.
• Intratester and intertester reliability refers to consistency of repeated measures
obtained by the same practitioner or between two practitioners, respectively.
• Reliability of continuous level data is calculated using intraclass correlation
coefficients, whereas the kappa coefficient is used for categorical level data.
• Internal consistency refers to the degree in which similar items on an outcome
measure yield similar scores and is represented by Chronbach’s alpha.
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O’Sullivan.

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Validity
• Validity is the degree to which an outcome measure is measuring
what it purports to measure.
• For example, the degree to which the Berg Balance Scale is
measuring balance.
• There are four basic types of validity:
1.Face validity
2.Content validity
3.Criterion-related validity
4.Construct validity
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Face validity
• Face validity, also called logical validity, is a simple form of validity
where you apply a superficial and subjective assessment of whether
your study or test measures what it is supposed to measure.
• Example: IQ tests are supposed to measure intelligence.
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FaceValidity: Definition and Examples - Statistics HowTo

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Content validity
• Content validity is how well an instrument (i.e. a test or
questionnaire) measures a theoretical construct.
• Content validity uses a more formal, statistics-based approach,
usually with experts in the field who judges the questions on how
well they cover the material.
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ContentValidity (Logical or RationalValidity) - Statistics HowTo

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Criterion validity
• Criterion validity (or criterion-related validity) measures how well
one measure predicts an outcome for another measure.
• Example: A job applicant takes a performance test during the
interview process. If this test accurately predicts how well the
employee will perform on the job, the test is said to have criterion
validity.
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CriterionValidity: Definition,Types ofValidity - Statistics HowTo

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Construct validity
• It demonstrates that the test is measuring the construct it claims it’s
measuring.
• Example: a doctor testing the effectiveness of painkillers on
chronic back sufferers. construct validity would test whether the
doctor was measuring pain and not numbness, discomfort,
anxiety or any other factor.
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ConstructValidity: Simple Definition, Statistics Used - Statistics HowTo,
Shuttleworth M

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Reliability vs.Validity
Reliability
• The consistency of measurement, or
the degree to which an instrument
measures the same way each time it
is used under the same condition
with the same subjects.
• Test-retest
• Internal consistency
Validity
• The strength of our conclusions,
inferences or propositions. Does it
measure what it is intended to
measure?
• Face
• Content
• Criterion
• Construct

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References
1. O’sullivan SB. Clinical Decision Making. In: Physical Rehabilitation. 6th ed. Philadelphia: F.A. Davis Co; 2014. p. 1–29.
2. Wiebe S, Guyatt G, Weaver B, Matijevic S, Sidwell C. Comparative responsiveness of generic and specific quality-of-life instruments. J. Clin.
Epidemiol. 2003;56 (1): 52-60.
3. Zeng Y., Zhou Y., Lin J., Zhou Y., Yu J. Generic and disease-specific quality of life and its predictors among Chinese inpatients with schizophrenia
Psychiatry Res. 2015; 228 (3): 724-728
4. Outcome Measures [Internet]. Physiopedia. 2012 [cited 2020 Aug 9]. Available from: https://www.physio-
pedia.com/Outcome_Measures#cite_note-5
5. Kingsley C, Patel S. Patient-reported outcome measures and patient-reported experience measures. BJA Education [Internet]. 2017 Apr [cited
2020 Aug 9];17(4):137–44. Available from: https://academic.oup.com/bjaed/article/17/4/137/2999278
6. Clinical Outcome Assessment [Internet]. Physiopedia. 2020 [cited 2020 Aug 16]. Available from: https://www.physio-
pedia.com/Clinical_Outcome_Assessment
7. Face Validity: Definition and Examples - Statistics How To [Internet]. Statistics How To. 2015 [cited 2020 Aug 16]. Available from:
https://tinyurl.com/y3qbk44c
8. Content Validity (Logical or Rational Validity) - Statistics How To [Internet]. Statistics How To. 2015 [cited 2020 Aug 16]. Available from:
https://tinyurl.com/y3e72dkl
9. Criterion Validity: Definition, Types of Validity - Statistics How To [Internet]. Statistics How To. 2015 [cited 2020 Aug 16]. Available from:
https://tinyurl.com/y3wcz726
10. Construct Validity: Simple Definition, Statistics Used - Statistics How To [Internet]. Statistics How To. 2014 [cited 2020 Aug 16]. Available from:
https://www.statisticshowto.com/construct-validity/
11. Martyn Shuttleworth. Construct Validity - Does the Concept Match the Specific Measurement? [Internet]. Explorable.com. 2020 [cited 2020 Aug
16]. Available from: https://tinyurl.com/y3g7vxda
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