Use Casea	Advantages	Limitations		Considerations
Diagnosis
Aid diagnosis of suspect cases, especially when RT‐PCR negative but X‐Ray/CT suggestive	May improve overall sensitivity of diagnosis Diagnosis of patients presenting late or for post‐infectious syndromes (low viral load) Diagnosis of patients when lower respiratory tract sampling not available	Unlikely to catch early‐stage infection (< 7 days) May not detect asymptomatic cases Negative test cannot rule out infection IgM appears early, but is less specific	Total antibody may have best sensitivity Should be confirmed by PCR, where possible Rising titres and seroconversion can improve sensitivity and specificity
Aid diagnosis of suspect cases when PCR is not available (would require careful development of interpretive guidelines)	As above and could enable decentralised/community testing in settings where the availability of PCR testing is limited.
Identification of individuals with protective immune status (conditional upon identifying correlates of protection for SARS‐CoV‐2)
Identify convalescent plasma donors	Treatment for critically ill patients	Ideal timing of collection unknown to optimise efficaciousness	Preferentially patients recovered from moderate to severe disease (high titre). Theoretically may be derived from vaccinated donors
CT: computed tomography; RT‐PCR: reverse transcription polymerase chain reaction;
aTable from Cheng 2020b