Q&A: Using codes Z21 and B20 for HIV patients

Q: I have a question about coding human immunodeficiency virus (HIV) and HIV-related illnesses. If a physician documents a patient is HIV positive, should the chart be coded to Z21? What about if they document the patient is HIV positive with an HIV-related illness—would that be coded to B20?

A: You are correct. The ICD-10-CM Official Guidelines for Coding and Reporting, Section I.C.1.a.2.f. says that patients who are HIV positive with any known prior diagnosis of an HIV related illness should be coded to code B20. Only confirmed cases are coded using code B20. HIV is one of three conditions that cannot be coded based on the documented terminology, “possible, probable, or suspected,” or any other similar terminology.

It is not required that any form of testing be documented, such as a positive serology test. The physician’s diagnostic statement that the patient is HIV positive with a prior HIV-related condition is all that is necessary for coding. Once a patient is coded to B20, they will always have B20 coded on their record; they will never go back to being coded using the asymptomatic code Z21.

Code Z21 is used for patients who are asymptomatic, meaning they are HIV positive but have never had an HIV-related condition. Once that patient experiences an HIV-related condition, the Z21 code is no longer appropriate. If the physician documentation states only that the patient is HIV positive, has HIV, or an HIV infection, a query would be required for clarification.

Editor’s Note: Sharme Brodie, RN, CCDS, CDI education specialist and CDI Boot Camp instructor for HCPro in Middleton, Massachusetts, answered this question. For information, contact her at sbrodie@hcpro.com. For information regarding CDI Boot Camps, click here.