PRO score interpretation thresholds (PROSITs)

Definition

PROSITs help us understand whether the magnitude of change in PRO scores are clinically meaningful - either at group level (between groups or within a group over time) or individual level (within single patients over time).

Note: Other terms are used inconsistently in literature to refer to similar concepts, e.g., minimal important difference (MID), minimal clinically important difference (MCID) or clinically relevant difference (CID). To address inconsistent terminology, the recently published SISAQOL-IMI guidelines (www.sisaqol-imi.org) propose the use of the umbrella term PRO score interpretation threshold.

Example

Application

e.g., when planning a study or reading a publication

• PROSITs thresholds vary between scales that measure quality of life but they can also differ in the same questionnaire depending the direction of change. In other words, the thresholds for improvement may be different to the thresholds for deterioration. Therefore, there is no ‘one size fits all’ approach and different PROSITs need to be established for different settings.
• An EORTC QOL Interpretation Guideline also covering PRO score interpretation thresholds will soon be published on the website of the EORTC QLG. 
  

Limitations

• Minimum number of two assessment times needed.
• The existing PROSITs for the use at group-level are primarily developed for clinical research and not recommended for the use in clinical practice.
• Currently, there are no established PROSITs for interpreting within-patient change for EORTC instruments. 

Available thresholds

For more information on PROSITs (former MIDs) for the EORTC QLQ-C30: Please refer to Musoro et al. (2023). The paper presents a diverse range of “MIDs” to help interpretation and inform more accurate sample size calculations for clinical trials with EORTC QLQ-C30 endpoints