Exploring the potential usefulness of the GCOS-16 for expanded applications.

The Genetic Counselling Outcome Scale-24 (GCOS-24) measures empowerment reliably in the context of genetic services, but its potential utility is constrained by some of its features. Using Rasch Measurement Theory, the GCOS-16 was developed: eight items were removed and the Likert scale collapsed from seven response options to three. The GCOS-16 has improved performance, and potential for usefulness beyond its original design i.e., identifying/triaging patients who may benefit most, and comparing genetic counseling (GC) to non-GC interventions. In this study, using the GCOS-24 data collected from a psychiatric GC clinic, we aimed to use a statistical method to determine the minimal clinically important difference (MCID) of the GCOS-16, and to examine whether the GCOS-16, or any individual items or subdomains could be used to identify patients who would most benefit from GC. The GCOS-24 data (24-items, 7-point Likert scale) from 307 charts were transformed into the GCOS-16 scoring (16 items, 3-point Likert scale). The GCOS-16 scores increased from pre- to post-GC (p < 0.001, d = 0.935), and the MCID was determined to be an increase of 2.5 points. There were significant differences between pre- to post-GC for all items and subdomains except for item #6. Patients receiving in-person GC were more likely to meet the MCID than those receiving service by telephone or telehealth (p < 0.001). Our data demonstrate that the GCOS-16 is sensitive to change in empowerment without ceiling effects - this could be used to triage patients for GC, and to compare GC to non-GC interventions.