Standardization is the means of implementing guidelines in medical
coding. These guidelines are used to delegate the appropriate codes
to document patient diagnoses as well as submission of procedure
codes. In an outpatient setting they refer to the first-listed diagnosis,
which is the equivalent of the primary diagnosis in an inpatient
setting. Primary diagnosis needs to meet medical necessity for the
procedure. It would be impossible to keep up with the codes
appropriate for billing if everyone was allowed to code according to
their own preferences. One major difference between inpatient and
outpatient coding is the coding of the reason for the visit is used in
outpatient coding, symptoms are coded when a condition is being
ruled out, and the final interpretation is used as diagnoses. For
example, if a patient has a sleep study snoring may be the reason for
the visit, hypersomnia a symptom and OSA can be the final diagnosis
based on a positive sleep study. If the study were negative the
snoring and hypersomnia would be the codes used. Standardization
allows diagnoses to be coded to the highest level of specification,
thereby leads to optimal reimbursement.
