SARS-CoV-2 Antibody Seroprevalence Among Maintenance Dialysis Patients in the United States

Walker, Adam G.; Sibbel, Scott; Wade, Curtis; Moulton, Nick; Marlowe, Gilbert; Young, Amy; Fadem, Stephen Z.; Brunelli, Steven M.

RATIONALE & OBJECTIVE: Reported COVID-19 cases underestimate the actual number of SARS-CoV-2 infections. Patients receiving maintenance dialysis are at high risk for COVID-19, and higher case rates have been reported relative to the general population. To better understand infection patterns, we performed a seroprevalence study among maintenance dialysis patients at a large dialysis organization in the United States. STUDY DESIGN: Cross-sectional SETTING & PARTICIPANTS: We measured IgG antibodies in an IRB-approved study of remnant serum samples collected for routine laboratory screenings in a national sample of 12,932 maintenance dialysis patients (27 May-01 Jul 2020). EXPOSURE: State, sex, age, and race. OUTCOMES: Seropositivity; ratio of seropositivity to known COVID-19 case rate. ANALYTIC APPROACH: Seropositivity was calculated overall and by state, sex, age, and race. Ratio of seropositivity to known COVID-19 cases was calculated overall and by state. RESULTS: Overall, 747 (5.8%) of samples were seropositive. Seroprevalence varied by state and was lowest in Kentucky (1.0%) but highest in New York (23.6%). Seroprevalence was similar among men and women. Among samples from patients < 70 years, 6.0%-6.5% were seropositive; whereas 5.2% and 3.9% of samples from patients 70-79 and ≥ 80 years, respectively, were seropositive. Samples from Black and Hispanic patients were 7.3% and 7.7% positive, respectively, compared to 2.8% of samples from White patients. After adjustment, risk differences among racial groups were lower, but not eliminated. During the study period, the known COVID-19 case rate was 3.3%. The ratio of seropositivity to known COVID-19 cases was 1.7. LIMITATIONS: Imperfect assay sensitivity; results represent infections occurring before July 2020; deidentification prevented comparison of antibodies to previous COVID-19 status for individual patients; may not generalize to patients dialyzing with other providers or in other countries. CONCLUSIONS: Seroprevalence was 5.8% among dialysis patients as of 01 July 2020. This indicates the actual number of infections was 1.7-times greater than reported cases. This ratio is lower than reported in the general population, suggesting there were fewer unknown infections among maintenance dialysis patients