Hi there. I want to ask a question about measuring performance based on biased samples of patients. It is said to be one controversy in disease management evaluation. Could you please kindly elaborate more for me?

No worries.

Thanks for the information.

Sure. Bias occurs if an unobservable or unmeasured characteristic of a patient makes it more or less likely that this patient has a positive (or negative) treatment effect and a higher (or lower) probability of responding well to the program intervention. A sample that only includes patients who agreed to participate in the program risks selection bias, for example, because these participants are likely to have greater motivation to take care of their health and, therefore, are more likely to benefit from the program intervention than the overall patient population. If so, analysis of the difference between that group and a comparison group will overstate the true effect of the intervention. You could read the below book for further information.

Mattke S, Bergamo G, Balakrishnan A (2006). Measuring and reporting the performance of disease management programs. Santa Monica, CA: RAND (WR-400).