Antibody (or serology) tests are used to detect previous infection with SARS-CoV-2 and can aid in the diagnosis of post-COVID conditions in patients without a previously confirmed SARS-CoV-2 infection. Awareness of a patient's vaccination status will aid in the interpretation of the serology test result. However, positive antibody results are not required to establish a diagnosis of post-COVID conditions, recognizing that among persons with diagnosed SARS-CoV-2, as many as 10%-20% may have no detectable antibodies. For information about antibody testing, see Using Antibody Tests for COVID-19.
Antibody test results should not be used to diagnose someone with an active SARS-CoV-2 infection. A positive SARS-CoV-2 viral test (ie, reverse transcription polymerase chain reaction [RT-PCR] test or antigen test) can be helpful for diagnosing current SARS-CoV-2 infection. Diagnostic testing is intended to identify current infection in individuals and is performed when a person has signs or symptoms consistent with COVID-19, or when a person is asymptomatic but has recent known or suspected exposure to SARS-CoV-2.
Option "D" is appropriate for the above reasons. In this patient, results of a SARS-CoV-2 antibody test were negative. However, recall that a positive antibody test is not required to establish a diagnosis of post-COVID conditions.
For more information about laboratory testing, see the laboratory testing section of the CDC interim guidance.
Public Information from the CDC and Medscape
Cite this: CDC Case Challenge: A Woman With Fatigue, Palpitations, and Headache - Medscape - Sep 02, 2021.