Ways to Identify Primary Diagnosis Codes

A primary diagnosis refers to the condition that caused the patient to be admitted to a hospital. Diagnosing the primary codes is an important part of the healthcare service delivered to patients. Here are some factors that help identify primary diagnosis codes.

Signs and Symptoms

The basic factors upon which a diagnosis is generally based are the signs and symptoms exhibited by the patient. Whenever a diagnosis is reached based on the signs and symptoms, it is referred to as a principal diagnosis. For instance, rose spots signify the occurrence of typhoid in a patient. Here, typhoid will be reported as the principal diagnosis. Similarly, a patient who has a cough and is diagnosed to be pneumonic by the doctor will have pneumonia written as his principal diagnosis.

Multiple Diagnoses

Sometimes, more than one diagnosis can be made. In this case, any diagnoses made can be reported as the principal diagnosis. For instance, if a patient arrives at the hospital with shortness of breath, the doctor might diagnose the symptom to be occurring due to either pneumonia or COPD. Here, both conditions can be established as diagnoses based on the symptom. Hence, any of the two can be reported as the principal diagnosis. If one of the diagnoses has more potential of being the reason for the symptom, it is usually sequenced first. However, if both have equal potential, it doesn’t matter how the diagnoses are sequenced.

Uncertain Diagnosis

So far, diagnoses have been easy. Either doctors have a clear idea of what the principal diagnosis is, or they have a few options that can be the reason. However, how do you code ones where the diagnoses are uncertain? In situations like this, medical reports are likely to have the following words:

  • Probable
  • Likely
  • Suspected
  • Questionable
  • Possible
  • Not ruled out

In cases like this, when the diagnoses are not confirmed, it should not be coded as such either. Here, outpatient coding guidelines are to be followed. However, this raises a question, what diagnosis would be made for admitting the patient to the hospital? After all, the short-term care is based on the diagnosis. Well, here, the coder can use the mentioned synonyms before writing the suspected diagnosis. Various measures should be taken to come to a suspected diagnosis. This includes a diagnostic workup, observation, and therapeutic approach.

Coding Complications

Sometimes, a patient is admitted to the hospital because of a complication that arose due to a surgery or treatment. How do you code the principal diagnosis in this case? Simple. You mention the complication as the primary diagnosis. These complication codes can be found in the ICD 10 code series T80-88. Surgery-related complication codes can be found in an ICD 10 code from T80-88.

Observation Unit Admission

Upon transfer from an observation unit to an inpatient facility, the principal diagnosis would be the condition that led to the transfer in the first place. For instance, let’s say a patient arrives for a surgery and is kept in the observation unit afterward. When in the observation unit, it is observed that the patient has had complications from the said surgery. When this patient will be transferred to an inpatient facility, the complication would be coded as the principal diagnosis.


As you can see, how you diagnose a patient is dependent on the situation as well as other factors. Make sure you are well-versed in these factors to ensure you correctly diagnose your patient. You are their healthcare provider. Don’t let them down.