This month’s issue opens with a new guideline, the “PRISMA-COSMIN for Outcome Measurement Instruments” (OMIs) [
1]. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [
2] are an established standard and the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) [
3] an influential initiative in our field. COSMIN’s methodological work supports the foundations of health-related quality of life and patient-reported outcome (PRO) research, for example with their taxonomy, terminology, and definitions of measurement properties for health-related PROs [
4], search filters [
5], and reporting and assessment of the quality of individual studies [
6]. The earlier development of a guideline and tools for systematic reviews of PRO measures [
7,
8] marked a step on the way to this guideline that covers systematic reviews of OMIs (defined as a “tool used to measure a health outcome domain”; [
1]) more broadly. …