Also relevant to the business necessity question is whether the employer requires similarly situated employees to submit to medical exams. Even if only one other employee is required to undergo a medical exam, the employer can establish business necessity by having good reasons to doubt the employee's ability to perform the essential functions of the job. Such doubts can be raised by the employee's request for accommodations, frequent absences, request for leave because of a medical condition, or behavior that poses a direct threat to his own safety or the safety of others.