Tip: COVID-19 antibody testing and CDI/coding professionals

CDI Strategies - Volume 14, Issue 19


The American Hospital Association recently published a Coding Clinic Advisor FAQ regarding ICD-10-CM coding for COVID-19. This article takes a closer look at the main topics addressed in the FAQ, including ICD-10-CM coding for COVID-19 antibody testing, virus signs and symptoms, and comorbidities.

Antibody testing and convalescent plasma therapy

Physicians and scientists are exploring new, innovative ways to stop the spread of COVID-19 while adhering to more lenient testing regulations released by the Food and Drug Administration in March. Hundreds of academic centers, hospitals, and private companies are working to create COVID-19 serology tests that detect the presence of COVID-19 antibodies in patients who have recovered from the virus.

Convalescent plasma therapy is one type of serology treatment that is the focus of clinical trials for COVID-19. This involves the transfusion of plasma from patients who have recovered from the virus to patients who are currently battling the virus. The antibodies bolster an immediate immune response in infected patients, allowing them to fight the infection rather than waiting on their own immune system to respond.

Convalescent plasma therapy has proven effective in the treatment of measles, mumps, and poliomyelitis. If a COVID-19 convalescent plasma therapy is approved for use during the national public health emergency, patients who were previously diagnosed with COVID-19 will be able to donate plasma to aid in the treatment of patients currently suffering from the virus.

However, as more serology tests become available, testing will extend to patients who have not previously been tested for COVID-19 but would like to determine if they have antibodies. The presence of antibodies would be used to identify individuals who were unknowingly infected with the virus.

There has been a lot of controversy surrounding the use of serology tests to allow “immunity passports” so healthy individuals can freely return to unrestricted work and travel. Infectious disease experts warn against the reliability of serology tests, and the World Health Organization recently stated that "there is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection.”

ICD-10-CM coding

Per the Coding Clinic Advisor guidance, coding professionals should use the following ICD-10-CM codes to report an encounter for antibody testing performed on a patient with resolved (a history of) COVID-19:

  • Z09, encounter for follow-up examination after completed treatment for conditions other than malignant neoplasm
  • Z86.19, personal history of other infectious and parasitic diseases

If the encounter for antibody testing is performed on a patient with unresolved COVID-19, the coder would instead report U07.1 (2019-nCoV acute respiratory disease).

If the encounter for antibody testing is not performed to confirm a current COVID-19 infection, nor is performed as a follow-up test after resolution of COVID-19, coders should assign ICD-10-CM code Z01.84 (encounter for antibody response examination).

When I first read this guidance, I found it odd that coders were not instructed to report an encounter for antibody testing in all these scenarios. However, I recalled that code Z01.84, much like Z03.818 (encounter for observation for suspected exposure to other biological agents ruled out), can only be used as a principal or first-listed code; therefore, it cannot be used as an additional code for an encounter.

Coders continue to have questions surrounding the appropriate reporting of codes Z01.84 and Z03.818 as well as codes Z11.59 (encounter for screening for other viral diseases) and Z20.828 (contact with and [suspected] exposure to other viral communicable diseases) during the national public health emergency. After this pandemic is over, wading through the coded information will be quite interesting considering the variety of opinions about the proper assignment of some of these codes.

Perhaps there would be less confusion surrounding COVID-19 reporting if the Cooperating Parties had created additional ICD-10-CM codes specific to COVID-19 encounters. Other than U07.1, ICD-10-CM codes used to report COVID-19 encounters are not specific to COVID-19. They describe conditions such as infectious and parasitic diseases, viral communicable diseases, and biological agents to viral disease.

Editor’s note: This article originally appeared in JustCoding. McCall is the director of HIM and coding for HCPro in Middleton, Massachusetts, and oversees all the Certified Coder Boot Camp programs. She works with hospitals, medical practices, and other healthcare providers on a wide range of coding-related custom education sessions. To read the rest of ACDIS’ coverage of the COVID-19 pandemic, click here.

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ACDIS Guidance, Clinical & Coding, News