What should be documented to ensure the integrity of a specimen?

The correct choice is the chain of custody. This concept is critical in the context of specimen integrity because it refers to the proper documentation and handling processes that track the specimen's journey from the point of collection to its analysis and eventual disposal. Each time the specimen is transferred or handled, a record is created to document who had possession of it, where it was, and how it was treated. This meticulous documentation helps to ensure that the specimen has not been tampered with or contaminated, thus guaranteeing the reliability and validity of the test results.

In contrast, other options mentioned do not directly impact or ensure the integrity of a specimen. Employee time sheets relate to attendance and work hours, annual budget reports concern financial planning and allocation of resources, while training records document personnel qualifications and competencies. While these may all be important in their respective areas, they don't serve the specific purpose of maintaining the integrity of specimen handling and testing processes.