Clinimetrics corner: the Global Rating of Change Score (GRoC) poorly correlates with functional measures and is not temporally stable.

The Global Rating of Change Score (GRoC) is a frequently used outcome measure that is used independently to measure improvements in a patient's condition or as an anchor for other outcomes measures. The tool has been criticized for recall bias, biases in administration, and for poor reliability over time. Our findings, captured from a sample of patients with shoulder impingement, suggest that all these concerns are of merit. Our results show poor correlation of the GRoC with functional measures after 2 and 3 weeks and decay of the associative stability of the GRoC from week to week.