Currently, there is no precise construct to handle age within timing and subset operators in a clear, consistent way. The “AGE AT” construct provides a simplified means for expressing the desired age range of a patient at the start time of an event. For the vast majority of measures it is important to provide bounds on the birthdate of the patient. In the current QDM this is represented using multiple “Patient Characteristic Birthdate: birth date” statements coupled with comparison operators. For example to specify that a patient must be at least 18 years old, but less than 85 before a given event, a measure would produce the following logic:

AND: “Patient Characteristic Birthdate: birth date” >= 18 year(s) starts before start of 
Encounter X
AND: “Patient Characteristic Birthdate: birth date” < 85 year(s) starts before start of 
Encounter X

Although this logic is reasonably straightforward, the pattern is common enough that providing a shorthand representation would eliminate many redundancies and increase overall expressiveness. The “AGE AT” operator provides this shorthand by providing a direct notation that is specific to determining a patient’s age before an event starts. For example the above logic would reduce to:

AND: 18 year(s) <= AGE AT(Encounter X) < 85 year(s)

This notation allows for quickly identifying that a measure explicitly looks for the patient’s age at the beginning of a given encounter, and provides a visual layout that conveys the bounds on the number of years.