High Prevalence of Asymptomatic COVID-19 Infection in Hemodialysis Patients Detected Using Serologic Screening

Abstract

Background: Strategies to minimize the risk of transmission and acquisition of COVID-19 infection in patients with ESKD receiving in-center hemodialysis have been rapidly implemented across the globe. Despite these interventions, confirmed COVID-19 infection rates have been high in the United Kingdom. Prevalence of asymptomatic disease in an adult hemodialysis population has not been reported. Also, to our knowledge, the development of humoral response to SARS-CoV-2 has not been previously reported in this population. Although serologic testing does not provide information on the infectivity of patients, seroprevalence studies may enable investigation of exposure within dialysis units and hence, assessment of current screening strategies.

Methods: To investigate the seroprevalence of SARS-CoV-2 antibodies in a hemodialysis population, we used the Abbott IgG assay with the Architect system to test serum samples from 356 patients receiving in-center hemodialysis for SARS-CoV-2 antibodies.

Results: Of 356 patients, 121 had been symptomatic when screened before a dialysis session and received an RT-PCR test; 79 (22.2% of the total study population) tested positive for COVID-19. Serologic testing of all 356 patients found 129 (36.2%) who tested positive for SARS-CoV-2 antibodies. Only two patients with PCR-confirmed infection did not seroconvert. Of the 129 patients with SARS-CoV-2 antibodies, 52 (40.3%) had asymptomatic disease or undetected disease by PCR testing alone.

Conclusions: We found a high seroprevalence of SARS-CoV-2 antibodies in patients receiving in-center hemodialysis. Serologic evidence of previous infection in asymptomatic or PCR-negative patients suggests that current diagnostic screening strategies may be limited in their ability to detect acute infection.

Keywords: COVID-19; dialysis; serology.

Figure 1.

Study flow diagram. Three hundred seventy-six patients were eligible for inclusion in the study and 356 were included in analysis. Flow chart indicates the number of patients in each group by PCR and antibody status. Neg, negative; Pos, positive.

Figure 2.

Raw data from SARS-CoV-2 IgG chemiluminescent microparticle immunoassay showing correlation between days from PCR testing and index result. (A) Scatterplot of the index value (sample/control [S/C]) relative light units for each sample tested. The manufacturer’s cutoff for a positive value (1.4) ±20% is indicated by dashed lines. (B) In the group of patients who were PCR tested, there is moderate positive correlation between the index value of antibody test and time from antibody testing to PCR testing. Statistical analysis performed using Spearman correlation. ***P<0.001.