Getting Scores on the Same Metric
The PROsetta Stone® project developed mathematical links between legacy measures and PROMIS® scores. This work takes a major step toward establishing the relationships between instruments that measure similar concepts.
PROsetta Stone linking applies and compares multiple methodologies to place the scores of two measures on the same metric. The result is a cross-walk table that associates each possible score on a "legacy" measure to a T-score of the comparable PROMIS instrument. For example, as shown on the left in Helpful Resources , the summed SF-36 Physical Function Scores have been linked to PROMIS Physical Function T-scores. A person using the SF-36 would calculate a physical function summed score, then use the table to find the equivalent score on PROMIS Physical Function.
The PROsetta Stone team has published results on depression, anxiety, physical function, pain, fatigue, and global health. See the list of many more measures that have linking tables here. More information on methodology and related publications are on the PROsetta Stone project website.
Depression Linking Tables
PROsetta Stone linking tables can be used to translate thresholds from one measure to the PROMIS metric. For example, several depression measures have thresholds for mild, moderate, and severe symptomatology. With PROsetta, thresholds across measures can be compared.
Choi, S.W., Schalet, B., Cook, K.F., & Cella, D. (2014). Establishing a Common Metric for Depressive Symptoms: Linking the BDI-II, CES-D, and PHQ-9 to PROMIS Depression. Psychological Assessment, 26(2), 513-527. http://dx.doi.org/10.1037/a0035768
What are some applications of linking?
Linking results, such as those obtained from PROsetta Stone, can inform data aggregation efforts. For example:
- Linking studies may support longitudinal studies. It may be necessary for longitudinal researchers to change measures over time, either due to researcher preference or because a scale is no longer age-appropriate (e.g. an adolescent scale is no longer valid in young adulthood). Results from a linking sub-study can enable such a switch.
- Linking may also reduce error in meta-analyses. Meta-analysts attempt to aggregate of results across studies, clinics, or nations using different measures on an interpretable common metric.
- The comparison of scores via linking can be further applied in quality improvement initiatives, where clinicians or hospitals are evaluated and compared relative to their peers.
Need to link multiple measures? Experienced HealthMeasures psychometricians and analysts are available to consult or collaborate on linking studies. To learn more, contact us.