To be able to obtain an ONC certification (and meaningful use funding for their clients) EHR vendors must follow a formal User Centered Design (UCD) process and perform summative usability testing on specific areas of the product.

We recommend that EHR vendors follow the ISO 9241-11 standard. ISO-9241 Part 11: (1998) pertains to the extent to which a product can be used by specified users to achieve specified goals with Effectiveness (Task completion by users), Efficiency (Task on time) and Satisfaction (responded by user in term of experience) in a specified context of use (users, tasks, equipment & environments).

User-Centered Design: Helping users become Effective, Efficient, and Satisfied

The effectiveness, efficiency and satisfaction with which specified users achieve specified goals in particular environments.

• Effectiveness: the accuracy and completeness with which specified users can achieve specified goals in particular environments
• Efficiency: the resources expended in relation to the accuracy and completeness of goals achieved
• Satisfaction: the comfort and acceptability of the work system to its users and other people affected by its use

Perhaps you are also interested in how these are measured and reported using the NIST CCIF format?