Clinical Ordering Practices of the SARS-CoV-2 Antibody Test at a Large Academic Medical Center (preprint)

ABSTRACT

Background: The novel severe acute respiratory coronavirus 2 (SARS-CoV-2) that causes COVID-19 originated in December 2019 and has now infected over 3 million people in the United States. In Spring of 2020, private laboratories and some hospitals began antibody testing despite lacking evidence-based guidance. Objective: To describe clinician-described indications for SARS-CoV-2 antibody testing, including cost implications, immediately following testing availability. Design: Retrospective chart review of patients who received antibody testing from May 14, 2020 to June 15, 2020. Setting: A large academic medical center, one of the first in the US to provide antibody testing capability to individual clinicians. Patients 447 consecutive patients who received SARS-CoV-2 antibody testing. Measurements Clinician-described indications for SARS-CoV-2 antibody testing, cost implications, and comparison with current expert-based guidance from the IDSA and CDC. Results: Of 444 individual antibody test results meeting inclusion criteria, the two most commonly described indications for ordering the antibody test, apart from public health epidemiology studies (n=223), were for patients with a now resolved COVID-19 compatible illness (n=105) with no previous molecular testing and in asymptomatic patients believed to have had a past exposure or contact with a person with COVID-19 compatible illness (n=60). The rate of positive SARS-CoV-2 antibody testing among those indications consistent with current IDSA and CDC guidance was 17% compared with 5% (p<0.0001) among those indications inconsistent with current IDSA and CDC guidance. Total cost estimates ranged from $57,720 to $97,680, of which 42% was for testing inconsistent with current expert-based guidance. Limitations: The duration of antibody response following infection is unclear and asymptomatic individuals may not develop a positive antibody response. Conclusions: Our findings demonstrate a dissociation between clinician described indications for testing and expert-based guidance and a significantly different rate of positive testing between these two groups. Clinical curiosity and patient preference appear to have played a significant role in testing decisions and substantially contributed to testing costs.