PROMIS Global Health Overview
The PROMIS Global Health is an overall evaluation of an adult (ages 18+) patient’s physical and mental health. The measure is generic rather than disease-specific and looks at a patient’s general health. There is only a fixed-length version consisting of 10 questions and is available at healthmeasures.net.
All versions of the PROMIS Global Health produces a Global Physical Health (GPH) and Global Mental Health (GMH) scoring component. There is not an overall PROMIS Global Health score. PROMIS also has shorter measures that will provide the GPH and GMH scores: Global Mental 2a and Global Physical 2a. These shorter measures produce scores that are less precise than the PROMIS Global Health.
Utilizing the T-score lookup algorithm (which CODE utilizes) all three version scores can be compared.
PROMIS Global Health Versions
There are three published versions of the measure:
- 1.0
- 1.1 (CODE implemented)
- 1.2 (Recommended)
The text of the questions and answers in all three versions are identical, except in version 1.1 and 1.2. ‘In the past 7 days’ associated with Global09 was removed, and the questions number was renamed to Global09r.
Version 1.2 was constructed to enable automatic Item Response Theory scoring. The following changes were made to enable that scoring.
- Global07, Global08, and Global10 were renamed to Global07r, Global08r and Global10r.
- Score values have been reversed to 5=None to 1=Very severe from the original version of 1=None to 5=Very severe.
- The scoring algorithm was changed so that users did not need to reverse the answer scores for Global08r and Global10r.
- Global07r responses can be submitted to the scoring algorithm with 0-10 responses and the scoring algorithm converts the scores automatically into 1-5 scores.
The table below outlines the differences in the versions.
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Global07 responses are recoded where 0 – No pain = 5, responses 1,2 and 3 = 4, responses 4,5,6 = 3, responses 7,8,9 = 2 and 10 – Worst pain imaginable = 1.
PROMIS Global Health Scoring
Multiple accepted scoring algorithms exist. The PROMIS scoring service utilizes Item Response Theory (IRT), a family of statistical models that connects individual questions to an assumed underlying trait or concept of global health represented by all items in the scale. To access this scoring methodology, one must use the PROMIS scoring service. IRT is particularly beneficial when there is missing data or different groups of participants respond to different sets of questions. As CODE requires responses to all questions and administers the same tool to all patient populations, CODE uses a scoring algorithm that calculates a raw score and identifies a scaled score based on PROMIS-provided tables.
In versions 1.0 and 1.1, the answer values for questions Global08 and Global10 were in the format of 1=None to 5=Very severe, and the scoring algorithm required reversing the scores before calculating the raw GPH and GMH scores that were used to determine the final T-scores.
Version 1.2 reverses the format of the answers for Global08r and Global10r to 5=None to 1=Very severe. The scoring instructions were modified to not require reversing the answer scores before calculating the raw score. The resulting raw GPH and GMH scores for v1.2 and v1.0/v1.1 are identical for the same responses, resulting in the same final T-score since all three versions utilize the same scoring table.
PROMIS recommends flipping the scores for Global08 and Global10 and renaming the questions to Global08r and Global10r when switching from PROMIS v1.0/v1.1 to v1.2.
PROMIS Global Health Score Interpretation
To calculate the GPH raw score, the tool sums up responses to questions Global03, Global06, Global07r (after conversion to a 5-point scale), and Global08r. The GMH raw score is calculated by adding responses to questions Global02, Global04, Global05, and Global10r. These raw scores determine the T-score.
A higher T-score from PROMIS indicates a higher level of the concept being measured, such as higher Global Physical Health or higher Global Mental Health. In the US general population, a T-score of 50 is the average with a standard deviation of 10. Therefore, a person with a T-score of 60 for GPH or GMH is one standard deviation healthier or better than the general population.
Conclusion
CODE can support version 1.1 or 1.2 of the PROMIS Global Health. All versions’ score components can be benchmarked against one another.
Utilizing Item Response Theory (IRT) scoring will produce different values than values calculated using the T-score look up method. Score components calculated using IRT should not be compared to the scores calculated using the T-score lookup methodology.
