COVID-19 Antibodies and Outcomes in Maintenance Hemodialysis Patients

Individuals at highest risk for adverse outcomes of SARS-CoV-2 infection include the elderly and those with pre-existing health conditions, including chronic kidney disease (CKD). CKD is an established risk factor for mortality and morbidity in the general population. Patients with end-stage kidney disease (ESKD) are at significantly high risk due to the risk for infection-related complications. Patients receiving in-center maintenance hemodialysis have been shown to be at increased risk for contracting COVID-19 compared with patients utilizing in-home dialysis.

Early studies from China, Italy, and England reported a COVID-19 incidence rate of 2% to 3% among outpatient hemodialysis centers, with mortality up to 30%. Those studies identified cases of COVID-19 based on clinical feature and/or positive quantitative, real-time, reverse-transcriptase PCR (RT-PCR) assays of nasopharyngeal swabs, performed primarily on symptomatic patients. PCR tests are prone to false-negative results, and COVID-19 is transmissible by asymptomatic patients, making the true incidence of COVID-19 infection in in-center hemodialysis patients unclear. Serologic SARS-CoV-2 IgG antibody testing in outpatient hemodialysis centers has been limited, but may help provide an improved assessment of SARS-CoV-2 epidemiology.

Minesh Khatri, MD, and colleagues conducted an analysis of data from three diverse outpatient dialysis units in the New York City area. Dialysis facilities in the New York City area had significant rates of COVID-19 infection between March and May 2020. The researchers utilized the data to examine asymptomatic transmission in the units, estimate rates of seroconversion, and identify characteristics associated with COVID-19 infection and hospitalization. Results were reported in Kidney360 [doi.org/10.34067/KID.0006292020].

The three units are in the New York University (NYU) Winthrop Outpatient Dialysis Network, affiliated with NYU Winthrop Hospital. Two of the three units are standalone; the third is centered within a subacute rehabilitation facility. Eligible patients with ESKD on in-center hemodialysis were active at one of the three units as of February 1, 2020. Patients receiving peritoneal dialysis or home dialysis were excluded. Follow-up was available through August 25, 2020.

The outcomes of interest were (1) overall prevalence of SARS-CoV-2 seropositivity in the three units; (2) proportion of patients who tested positive for SARS-CoV-2 RT-PCR who developed antibodies; (3) proportion of patients who were asymptomatic who developed antibodies; and (4) severity of COVID-19 (defined as requiring hospitalization). Only hospitalizations for COVID-19 specifically were counted.

There were 386 patients registered at the three units as of February 1, 2020. Of those, 367 met inclusion criteria and had either SARS-CoV-2 PCR (n=156) or IgG antibody (n=343) tests. Of the 367, 104 were COVID-19 positive and 263 were COVID-19 negative. Median age for the overall cohort was 68 years, 44% were female, 45% were White, 34% were Black, and 17% were Hispanic.

Patients in the COVID-19 positive group were significantly younger (65 years vs 69 years) and were more likely to be Black (43% vs 30%) or Hispanic (32% vs 12%) than patients in the COVID-19 negative group. Patients in the COVID-19 positive group were also more likely to have used taxis and ambulettes and less likely to have used personal transportation to and from the dialysis center than patients in the COVID-19 negative group.

There was significant variation in COVID-19 positivity among the three dialysis units. The highest disease prevalence was in the subacute rehabilitation facility-based unit (Sun Harbor), with 70% of patients affected. There was also a difference in prevalence between the two standalone, community-based dialysis units: 32% of patients at the Mineola center were affected versus 7% of patients at the Bethpage center. The Mineola unit had a higher percentage of Black (44% vs 6%) and Hispanic patients (22% vs 6%), compared with the Bethpage unit, despite the Bethpage unit having more comorbidities, including older age, vascular disease, and chronic obstructive pulmonary disease (COPD).

Of the 104 patients who tested positive for COVID-19, 35% (n=36) were hospitalized. Fifteen of the 104 patients (14%) died. There were no significant differences between the patients who were hospitalized and those who were not hospitalized, with the exception of greater prevalence of COPD. The mortality rate among the hospitalized patients was 33% (12/36).

There was universal seroconversion among the patients who tested positive for COVID-19 by PCR (n=67) and who underwent IgG antibody testing (n=51). Sixteen patients who had a positive PCR test did not have antibody testing. Asymptomatic transmission, defined as patients who had IgG antibodies and either were not given a PCR test (no indication) or were a person under investigation with a negative PCR result, occurred in 32% of patients (28/88).

Limitations to the study cited by the authors included the inability to rule out false positives or false negatives to the serologic testing, not including patients on home dialysis, lack of data on rates of infection among dialysis staff, and the small sample size.

In conclusion, the researchers said, “We found that all patients on dialysis mounted an antibody response to symptomatic infection, and there was a significant rate of asymptomatic spread in dialysis units, as determined on the basis of serologic testing. There were high rates of hospitalization of patients who were symptomatic and subsequent mortality, and there were also substantial racial/ethnic disparities in this population, as well. The durability and efficacy of antibodies needs to be confirmed in larger and longer studies.”

Takeaway Points

1. Researchers in New York conducted a study to examine asymptomatic transmission of COVID-19 infection at three diverse outpatient dialysis units. The study also assessed the patient characteristics associated with COVID-19 infection and hospitalization.
2. Of 367 patients, 28% (n=104) had either a positive PCR or IgG test. There was wide variation in COVID-19 positivity among the three centers.
3. Among this patient population, rates of asymptomatic infection were high, as were rates of hospitalization and mortality.