Once a patient has developed an HIV-related illness, what code should be assigned on every subsequent admission?

The correct response is that once a patient has developed an HIV-related illness, the code that should be assigned on every subsequent admission is B20. This code is used for HIV disease and indicates that the patient has been diagnosed with the condition and consequently has developed manifestations indicative of a progression to AIDS.

Choosing the right code is crucial for accurate medical documentation and reporting. B20 is sanctioned for cases where HIV has advanced to a stage that includes other illnesses, thus it rightly captures the patient's ongoing condition and aids in reflecting the severity of their health status.

The other codes pertain to different situations—Z21 indicates asymptomatic HIV infection status, R75 is used for inconclusive laboratory results for HIV, and O98.7- pertains to HIV during pregnancy, childbirth, or the puerperium. Thus, they would not be applicable for continuous admissions following the onset of an HIV-related illness.