It is crucial to emphasize on the importance of proper coding of diagnosis resulting in preciseness.

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Importance of Listing Primary Diagnosis Code first
The main purpose of a diagnosis is to determine, within a certain degree of accuracy, the
underlying CAUSE of the patient’s condition. It is very critical to stress the importance of
proper medical coding of a diagnosis. Accuracy, to the highest possible degree, is essential
to reimbursement for services rendered; and to protection from both malpractice and civil
litigation. One often hears the term, principal diagnosis, primary diagnosis and first-listed
diagnosis. Coders are often confused, as with some healthcare providers, what term should
be used, not only when, but also under what circumstances of the patient. It is very
important to understand the various terminologies that are often used interchangeably
dependent on the patient’s situation before applying various terms
The definition of principal diagnosis (originally developed in 1985) under the Uniform
Hospital Discharge Data Set (UHDDS) is said to apply only to inpatients during acute, short-
term, long-term care and psychiatric hospitals, dependent on length of stay parameters.
Below are the definitions of the different terms for principal diagnosis:
 First-listed diagnosis: Terms “principal” and “primary” are often used
interchangeably to define the diagnosis that is sequenced first. The term first-listed
diagnosis/condition is used in the outpatient setting in lieu of principal diagnosis, and
because of the timing. Moreover, in cases of an existence of a discrepancy, it is the
first-listed diagnosis as per the coding conventions of ICD-10-CM, along with the
general and disease-specific guidelines within ICD-10-CM, which will have

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precedence over the outpatient guidelines. Outpatient surgery encounter rules are
to assign the diagnosis code as first-listed for the condition that the surgery was
performed.
 Principal diagnosis: Condition established after study to be chiefly responsible for
the patient’s admission to the hospital. It is always the first-listed diagnosis on the
health record and the UB-04 claim form. This direction applies to nursing homes as
stated in the guidelines.
 Primary diagnosis: This term is often used to indicate the reason for the continued
stay in the LTC facility. It is also used interchangeably with principal diagnosis.
The primary diagnosis should be listed first. Other additional codes for any coexisting
conditions are to be then listed. It should be remembered that, your diagnosis—the
disorder you are evaluating and/or treating—is considered the primary diagnosis and
should be listed first on the claim form. Other supporting diagnoses are considered
secondary and should be listed after your primary diagnosis. In today’s medical parlance,
Primary diagnosis is now termed as first-listed diagnosis.
Dos and Don’ts when coding using first-listed diagnosis
 Therapeutic services received only during an encounter/visit, the diagnosis should
first be sequenced, followed by condition. Problem or other reason should be
assigned as secondary codes. However, when the primary reason is chemotherapy or
radiation therapy, or rehabilitation, the exception here is, the appropriate V code for
the service should be listed first, and the diagnosis or problem for which the service
is being performed listed second.
 It has been stressed by the guidelines laid down that the outpatient surgery
encounter rules are to assign the diagnosis code as first-listed for the condition that
the surgery was performed. But, in case there is a difference between the
postoperative diagnosis & the preoperative diagnosis when the diagnosis is
confirmed, the postoperative diagnosis or condition would be the most definitive
diagnosis. Thus, the first-listed diagnosis or condition is governed by circumstances
of admission, reflecting the reason the patient is present for the care.

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 It is noteworthy to understand here that, especially in the outpatient setting, codes
for other diagnoses (e.g., patients treated for chronic conditions including
medication management) and care should be sequenced as additional diagnoses and
not as the first-listed diagnosis.
 Take note that, chronic conditions may not always be the reason the condition is
treated during the visit. But, the main reason for the visit, or what was addressed
during the visit, should be the first diagnosis listed. For instance, in the case of a
patient with a history of asthma, if the physician codes the exacerbation of the
chronic condition – severe wheezing, coughing, chest tightness of breath, as the first-
listed diagnosis, the reason for the encounter and codes as secondary diagnosis the
chronic asthma, the claim is likely to be reimbursed.
 The place of service should never dictate the diagnostic code, only the
documentation.
 Do remember that E-codes assigned most regularly in the emergency department,
should never be assigned as a first-listed diagnosis.
 When using V codes, usually implemented for occasions when circumstances other
than a disease or injury are recorded as a diagnosis or problem, they may be used as
either a first-listed or as additional diagnosis, but depends on the circumstances of
the encounter/visit. For instance, routine outpatient prenatal visits which exhibit no
complications V22.0, or V22.1, as the first-listed diagnosis can be used
 If two or more diagnoses equally meet the definition for principal diagnosis, either
diagnosis can be sequenced as the first-listed diagnosis
 According to Medicare Rules, the principal (first-listed diagnosis) is the clinical
diagnosis, in absence of a definitive pathologic diagnosis, at the time a claim is filed
Many of the codes may be interpreted as applying to more than one area with a slightly
different description relating that code to that anatomical area. There are very specific
rules that must be followed in the assigning of the codes. Medicare has historically set the
precedent and standard which all other carriers follow. Group insurance, HMO's, PPO's,
auto insurers and worker's compensation, all follow the precedents set by Medicare.