Which of the following methods could be used to detect the presence of COVID-19 antibodies in a patient’s serum?

• A. Administering a COVID-19 vaccination to the patient.
• B. Testing the patient’s serum with a direct antibody test.
• C. Testing the patient’s serum with an indirect antibody test.
• D. Providing the patient with COVID-19 immune globulin therapy.
• E. None of the above.

Answer: (C)

Verified step by step guidance

1. Understand the difference between direct and indirect antibody tests: a direct antibody test detects antibodies bound to antigens on pathogens, while an indirect antibody test detects antibodies present in the patient's serum by using known antigens.
2. Recognize that to detect COVID-19 antibodies in a patient's serum, you need a method that identifies antibodies circulating in the blood, which is what an indirect antibody test does.
3. Eliminate options that do not involve testing the serum directly for antibodies, such as administering a vaccine or providing immune globulin therapy, since these are treatments, not diagnostic tests.
4. Recall that a direct antibody test typically detects antigens or antibodies bound to cells or pathogens, not free antibodies in serum, so it is not suitable for detecting serum antibodies.
5. Conclude that the appropriate method to detect COVID-19 antibodies in serum is the indirect antibody test, which uses known viral antigens to capture and identify patient antibodies.