The SPIRIT guidance states that: “Where possible, the development and adoption of a common set of key trial outcomes within a specialty can help to deter selective reporting of outcomes and to facilitate comparisons and pooling of results across trials in a meta-analysis. The COMET (Core Outcome Measures in Effectiveness Trials) Initiative aims to facilitate the development and application of such standardised sets of core outcomes for clinical trials of specific conditions (www.comet-initiative.org). Trial investigators are encouraged to ascertain whether there is a core outcome set relevant to their trial and, if so, to include those outcomes in their trial. Existence of a common set of outcomes does not preclude inclusion of additional relevant outcomes for a given trial.”
The ISRCTN registry is a primary clinical trial registry recognised by WHO and ICMJE. The ISRCTN guidance for registration states: You should refer to the COMET (Core Outcome Measures in Effectiveness Trials) initiative which aims to develop “core outcome sets”, that is, agreed outcome measures reported for all trials in a particular field and how these outcomes should be measured.