Which condition can never be assigned as a principal diagnosis?

To understand why the correct choice is R65.2, it’s important to recognize what the code represents. R65.2 stands for "Systemic inflammatory response syndrome (SIRS) of non-infectious origin." Codes like these are often secondary diagnoses rather than principal diagnoses. This is because the principal diagnosis must determine the reason for the patient's admission, and SIRS usually arises as a complication of another underlying condition rather than as a stand-alone diagnosis.

In the context of coding, a principal diagnosis should capture the primary reason for the patient's encounter or admission. Since R65.2 describes a syndrome that is typically secondary to another condition, it cannot be assigned as the principal diagnosis.

Other choices correspond to conditions that can serve as principal diagnoses. A15.0 represents "Tuberculosis of the lung, confirmed by culture," which is a clear reason for admission. J12.81 is for "COVID-19," which can also be a principal diagnosis. Lastly, B97.21 refers to "SARS-CoV-2 virus," and in the context of a COVID-19 diagnosis, this can serve as a principal diagnosis as well.

Understanding how to determine which codes can be principal diagnoses is crucial for accurate coding, thus reinforcing