Solving the Tower of Babel Problem for Patient-Reported Outcome Measures : Comments on: Linking Scores with Patient-Reported Health Outcome Instruments: A Validation Study and Comparison of Three Linking Methods

Equating and linking Patient-Reported Outcomes Measurement Information System 29-item questionnaire and 36-item Short-Form Health Survey domains using Rasch modeling

OBJECTIVES

To develop a simple, practical methodology to equate or link equivalent domains of the 36-item Short-Form Health Survey (SF-36) and the Patient-Reported Outcomes Measurement Information System 29-item questionnaire (PROMIS-29) using the Rasch framework.

STUDY DESIGN AND SETTING

In April 2016, the PROMIS-29 and SF-36 were completed by 1501 individuals selected to be representative of the French population. For each domain common to the two questionnaires, a Partial Credit Model was fitted to the items related to that dimension in the two questionnaires. These items were then calibrated on the same metric, which enabled the scores from one questionnaire to be associated with the scores from the other.

RESULTS

Six of the seven PROMIS-29 scales and five of the six SF-36 subscales (physical, pain, social, vitality, depression and anxiety domains) were equated or linked. Correspondence tables between scores, with a 95% confidence interval, were established for each domain. A freely available Stata macro program was developed to automatize the equating or linking process.

CONCLUSION

These results should facilitate comparisons across studies using the SF-36 and the PROMIS-29 in France. The equating or linking process developed is simple to implement and can be used in other countries and for other instruments.

Overcoming floor and ceiling effects in knee arthroplasty outcome measurement

Aims

To map the Oxford Knee Score (OKS) and High Activity Arthroplasty Score (HAAS) items to a common scale, and to investigate the psychometric properties of this new scale for the measurement of knee health.

Methods

Patient-reported outcome measure (PROM) data measuring knee health were obtained from the NHS PROMs dataset and Total or Partial Knee Arthroplasty Trial (TOPKAT). Assumptions for common scale modelling were tested. A graded response model (fitted to OKS item responses in the NHS PROMs dataset) was used as an anchor to calibrate paired HAAS items from the TOPKAT dataset. Information curves for the combined OKS-HAAS model were plotted. Bland-Altman analysis was used to compare common scale scores derived from OKS and HAAS items. A conversion table was developed to map between HAAS, OKS, and the common scale.

Results

We included 3,329 response sets from 528 patients undergoing knee arthroplasty. These generally met the assumptions of unidimensionality, monotonicity, local independence, and measurement invariance. The HAAS items provided more information than OKS items at high levels of knee health. Combining both instruments resulted in higher test-level information than either instrument alone. The mean error between common scale scores derived from the OKS and HAAS was 0.29 logits.

Conclusion

The common scale allowed more precise measurement of knee health than use of either the OKS or HAAS individually. These techniques for mapping PROM instruments may be useful for the standardization of outcome reporting, and pooling results across studies that use either PROM in individual-patient meta-analysis.

Can a linking crosswalk table be applied to a different population? An independent validation study for a crosswalk between BSI depression and PROMIS depression scales

A linking procedure establishes a "bridge" between the scores from different patient-reported outcome (PRO) instruments that measure similar constructs. After developing a linking relationship however, it is critical to evaluate whether this relationship can be generalized to different groups. Our study aims to validate a published crosswalk for score conversion between the Brief Symptom Inventory Depression subscale and the Patient-Reported Outcomes Measurement Information System Depression 8a using an independent sample. Data were from a sample of young men who have sex with men (MSM), which differs in terms of participant age, race, and ethnicity from the sample used to develop the existing crosswalk. The validity of the newly derived crosswalk was evaluated in terms of the correlation, mean difference and standard deviation between the observed and the linked scores. The two crosswalks were further compared to evaluate if the difference was within an acceptable range. More than half of the item parameters obtained from the two samples were found to overlap in their confidence intervals. Differences between each pair of scores in the two crosswalks was within three T-score points, well within the range of each crosswalk score's standard error. This study concludes that an existing crosswalk is replicable on a sample that differs from that used for crosswalk development, but future research should continue to examine the generalizability of the linked parameters and evaluate the reproducibility of this crosswalk to other populations.

A Patient Reported Outcome Ontology: Conceptual Issues and Challenges Addressed by the Patient-Reported Outcomes Measurement Information System® (PROMIS®)

We briefly review the history of measuring perceptions of health and quality of life, followed by an examination of conceptual issues related to terminology that have led to potentially conflicting ontologies. Then, we discuss challenges posed by the lack of consensus on common meaning and the proliferation of measures. Next, we suggest a solution grounded in an ontology adopted by the National Institutes of Health (NIH) funded Patient-Reported Outcomes Measurement Information System (PROMIS) project. We conclude by discussing issues associated with mapping the PROMIS domain framework onto other familiar ontologies and recommend a way forward for PROMIS to provide a sustainable ontological structure to enable coherent common measurement.