The inclusion of time in the definitions of levels of E/M services has been
implicit in prior editions of CPT®. The inclusion of time as an explicit factor beginning
in CPT® 1992 is done to assist in selecting the most appropriate level of E/M services.
It should be recognized that the specific times expressed in the visit code descriptors
are averages and, therefore, represent a range of times which may be higher or lower
depending on actual clinical circumstances.
Time is not a descriptive component for the emergency department levels of E/M
services because emergency department services are typically provided on a variable
intensity basis, often involving multiple encounters with several patients over an
extended period of time. Therefore, it is often difficult to provide accurate estimates
of the time spent face-to-face with the patient.
Studies to establish levels of E/M services employed surveys of practicing physicians
to obtain data on the amount of time and work associated with typical E/M services.
Since “work” is not easily quantifiable, the codes must rely on other objective,
verifiable measures that correlate with physicians’ estimates of their “work.” It has
been demonstrated that estimations of intraservice time (as explained below), both
within and across specialties, is a variable that is predictive of the “work” of E/M
services. This same research has shown there is a strong relationship between
intraservice time and total time for E/M services. Intraservice time, rather than total
time, was chosen for inclusion with the codes because of its relative ease of
measurement and because of its direct correlation with measurements of the total
amount of time and work associated with typical E/M services.