A Quality Improvement Project to Minimize COVID-19 Infections in Patients Receiving Haemodialysis and the Role of Routine Surveillance Using Nose and Throat Swabs for SARS-CoV-2 rRT-PCR and Serum Antibody Testing.

BACKGROUND: Patients receiving in-centre haemodialysis (ICHD) are highly vulnerable to COVID-19. OBJECTIVE: We created a quality improvement (QI) project aimed to eliminate outbreaks of COVID-19 in haemodialysis units and evaluated the utility of surveillance rRT-PCR test and SARS-CoV-2 serum antibodies for prompt identification of patients infected with COVID-19. METHODS: A multifaceted QI programme including a bundle of infection prevention control (IPC) measures was implemented across 5 ICHD units following the first wave of the pandemic in June 2020. Primary outcomes evaluated before and after QI implementation were incidence of outbreaks and severe COVID-19 illness defined as COVID-19-related death or hospitalization. Secondary outcomes included the proportion of patients identified in the pre-symptomatic/asymptomatic phase on surveillance rRT-PCR screening and the incidence and longevity of SARS-CoV-2 antibody response. RESULTS: Following the implementation of the QI project, there were no further outbreaks. Pre- and post-implementation comparison showed a significant reduction in COVID-19-related mortality and hospitalization (26 vs. 13 events, respectively, p < 0.001). Surveillance rRT-PCR screening identified 39 asymptomatic or pre-symptomatic cases out of a total of 59 rRT-PCR-positive patients (39/59, 66%). SARS-CoV-2 antibody levels were detected in 72/74 (97%) rRT-PCR-positive patients. Amongst rRT-PCR-positive patients diagnosed before August 2020, 96% had detectable antibodies until January 2021 (days from the rRT-PCR test to last antibody testing, 245-280). CONCLUSIONS: Systematic implementation of a bundle of IPC measures using QI methodology and surveillance rRT-PCR eliminated outbreaks in HD facilities. Most HD patients mount and sustain antibody response to COVID-19 for over 8 months.

Paired sensitivity analysis of four SARS-CoV-2 serological immunoassays in a longitudinal cohort of convalescent hospital staff.

BACKGROUND: SARS-CoV-2 serological testing has seen extensive academic and clinical use from investigating correlates of immunity to seroprevalence, convalescent plasma and vaccine trials. Interpretation of these studies will depend on robust validation of the longitudinal sensitivities of these assays, especially in the context of mild disease which makes up the majority of the Coronavirus Disease 2019 (COVID-19) caseload. METHODS: Hospital staff (n = 94) returning to work following polymerase chain reaction confirmed COVID-19 were offered antibody testing to assist with laboratory verification. Initial specimens were collected at median 29 days post-symptom onset and run on the Roche, Abbott, Siemens and DiaSorin platforms. Re-sampling occurred at median 142 days from a subset of the initial cohort (n = 62) that had volunteered to provide further serum samples to assist in longitudinal sensitivity analysis. Samples that were not run across all four platforms were excluded from analysis. RESULTS: Comparative sensitivity analysis was conducted on 89/94 of the initial specimens and 55/62 of the repeat specimens. Sensitivity at initial sampling ranged from 78 to 87% across platforms. At re-sampling, sensitivities were: 100% (Roche), 45% (Abbott), 100% (Siemens), and 80% (DiaSorin). Paired analysis using the longitudinal cohort (n = 55) demonstrated stable or increasing median assay values on three platforms, with a clear reduction seen only on the Abbott platform (4.78 to 1.34) with corresponding sensitivity drop-off (81.8% to 45.4%). CONCLUSION: The Abbott assay demonstrated sensitivity drop-off and decrease in median assay signal below detection threshold at four to five months. This has implications on the interpretation and design of future studies.