Abstract
Background: The objective of this analysis was to compare the performance sensitivity and specificity of manufacturer-recommended signal-to-cutoff (S/Co) thresholds with modified S/Co values to estimate the prevalence of SARS-CoV-2-specific antibodies in a cohort of firefighters with a known infection history.
Methods: Plasma venipuncture samples were used for serologic analysis of firefighters in Los Angeles, CA, USA, in October 2020. Seropositivity was assessed using the manufacturer’s recommended S/Co (≥1.4 IgG) and modified S/Co thresholds based on measured antibody levels in 178 negative control patients who had blood drawn prior to the emergence of COVID-19. Optimal S/Co threshold was determined by receiver operating characteristic (ROC) curve analysis.
Results: Of 585 firefighters included in the study, 52 (8.9%) reported having a PCR-positive test history prior to antibody testing. Thirty-five (67.3%) firefighters with a previous PCR-positive test were seropositive based on the manufacturer S/Co thresholds, consistent with an estimated 67.3% sensitivity and 100% specificity. After evaluating multiple modified S/Co thresholds based on pre-pandemic negative samples, a modified S/Co of 0.36 was found to yield optimal sensitivity (88.5%) and specificity (99.4%) by ROC curve analysis. This modified threshold improved serostatus classification accuracy by 21.2%.
Conclusions: S/Co thresholds based on known negative samples significantly increase seropositivity and more accurately estimate cumulative incidence of disease compared to manufacturer-based thresholds.
【초록키워드】 COVID-19, IgG, Antibody testing, antibody, Infection, Prevalence, sensitivity, specificity, Cohort, ROC, Accuracy, Sensitivity and specificity, serologic analysis, Patient, Seropositivity, incidence, USA, threshold, characteristic, serostatus, disease, seropositive, Blood, Analysis, ROC Curve, Los Angeles, SARS-CoV-2-specific antibody, PCR-positive, cumulative, thresholds, venipuncture, negative sample, negative control, significantly, reported, was determined, were used, 【제목키워드】 SARS-CoV-2, firefighter, Los Angele,