January 6, 2017

Outcome measures

Description
An outcome measure is the method used to assess the effect of an intervention. The purpose of an outcome measure is to:

1. Discriminate among subjects at one point in time
2. Predict a subsequent event or outcome
3. Assess change over time.

Standardized outcome measures
1. Have explicit instructions for administering, scoring, and interpreting results
2. They are supported to the extent that information concerning their measurement properties has been estimated, reported, and defended in the peer-reviewed literature.
3. The outcome measure is valid, reliable, sensitive and specific. 

Measures of validity
1. The outcome measure assess what it is intended to measure (face validity)
2. The outcome measure is appropriate for the population of interest (content validity)
3. The outcome measure provides results that are consistent with the gold standard (criterion validity)

Measures of reliability
1. Multiple assessments of one individual will provide consistent results (test-retest/absolute reliability)
2. The outcome measure can determine the degree to which the condition exists (relative reliability)

Sensitivity
The ability of a test to reliability detect the presence of a condition. Therefore, if the test is negative, the subject will not have the condition (true positives / total positive results; SNOUT rules out).

Specificity
The ability of a test to reliably detect the absence of a condition. Therefore, if the test is positive, the subject will have the condition (true negatives / total negative results; SPIN rules in)