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

Abstract

Rationale & objective: Reported coronavirus disease 2019 (COVID-19) cases underestimate the actual number of severe acute respiratory syndrome coronavirus 2 (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 immunoglobulin G antibodies in an institutional review board-approved study of remnant serum samples collected for routine laboratory screenings in a national sample of 12,932 maintenance dialysis patients (May 27 to July 1, 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. The ratio of seropositivity to known COVID-19 cases was calculated overall and by state.

Results: 747 (5.8%) samples were seropositive. Seroprevalence varied by state and was lowest in Kentucky (1.0%) and highest in New York (23.6%). Seroprevalence was similar among men and women. Among samples from patients younger than 70 years, 6.0% to 6.5% were seropositive; whereas 5.2% and 3.9% of samples from patients aged 70 to 79 and 80 years or older, respectively, were seropositive. Samples from Black and Hispanic patients were 7.3% and 7.7% positive, respectively, compared with 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 July 1, 2020. This indicates that the actual number of infections was 1.7 times greater than reported cases. This ratio is lower than reported in the general population, suggesting that there were fewer unknown infections among maintenance dialysis patients.

Keywords: COVID-19; SARS-COV-2; antibodies; coronavirus; hemodialysis.

Graphical abstract

Figure 1

Seroprevalence of remnant samples by sample collection week. Plotted are the proportion of patient samples that were positive for immunoglobulin G and 95% confidence limits. Overall seroprevalence is depicted by the center line on the diamond, with 95% confidence limits represented by the top and bottom peaks.

Figure 2

Seroprevalence by patient sex, age, and race. Plotted are the proportion of patient samples that were positive for immunoglobulin G and 95% confidence limits. Overall seroprevalence (dashed lines) and 95% confidence limits (gray rectangle) shown for reference.