Subjects and data
Surveillance of new cases of COVID-19 in dialysis facilities in Japan was initiated by the COVID-19 Task Force Committee of the Japanese Association of Dialysis Physicians, the Japanese Society for Dialysis Therapy, and the Japanese Society of Nephrology on April 8, 2020 [3]. This registry was used to collect data of dialysis patients; data of a total of 1,948 dialysis patients with COVID-19 who were registered by June 19, 2021, were extracted. Among those, data of 897 patients (893 patients whose outcome was unknown and 4 patients whose age was unknown) were excluded, and a total of 1010 patients were included in this analysis.
Patient background data (age, gender, primary disease, duration of dialysis, complications, oxygenation, treatment for COVID-19) were collected; however, smoking status data were not collected. Blood test data at the time of diagnosis or hospitalization [albumin, blood urea nitrogen, creatinine, C-reactive protein (CRP), white blood cell count, hemoglobin, and platelet count] were available in patients who registered after March 16, 2021; these data were collected from a total of 311 patients whose blood test data were available. Treatment policy by the Ministry of Health, Labour and Welfare in Japan was implemented in which dialysis patients diagnosed with COVID-19 are treated with hospitalization [3].
Overall survival of patients was investigated with stratification by age group, complication status, and treatment. In terms of treatment for COVID-19, the efficacy of remdesivir was investigated among matched patients by using propensity score for age and oxygenation [with or without oxygen supplementation, ventilator, or extracorporeal membrane oxygenation (ECMO)] at the ratio of 1:3 for the patient group treated with remdesivir and the patient group not treated with remdesivir. The duration of hospitalization was also compared between the patient group treated with remdesivir and the patient group not treated with remdesivir. In terms of dialysis, overall survival was compared between patients who underwent peritoneal dialysis and those who underwent hemodialysis matched using the propensity score for age and oxygenation (with or without oxygen supplementation, ventilator, or ECMO) at the ratio of 1:3.
Statistical analysis
Categorical data were analyzed using Fisher’s exact test, and continuous data were analyzed using Welch’s t test or Mann–Whitney’s U-test. For survival analysis, the survival probability was estimated by Kaplan–Meier methods and compared using log-rank test. The multiplicity was adjusted by Bonferroni method. Hazard ratios and associated 95% confidence intervals were assessed by Cox regression hazard model.
The univariate and multivariate analyses were performed to identify the risk factor of mortality, with incidence of COVID-19 in facilities (less than 5 or more than 5), age (< 60, 60 s, or ≥ 70), gender, primary disease (chronic glomerulonephritis, diabetes mellitus, nephrosclerosis, or others), duration of dialysis (< 1 year, 1 to < 5 years, 5 to < 10 years, 10 to < 15 years, or ≥ 15 years), complications (diabetes mellitus, hypertension, cardiovascular disease, peripheral arterial disease, or malignancy), oxygenation (with or without oxygen supplementation, ventilator, or ECMO), treatment for COVID-19 (with or without remdesivir or dexamethasone) as independent variables. The univariate and multivariate analyses were performed to identify the risk factors of mortality also in those who had blood test data at the time of diagnosis or hospitalization, with age (< 60, 60 s, or ≥ 70), gender, primary disease (chronic glomerulonephritis, diabetes mellitus, nephrosclerosis, or others), duration of dialysis (< 1 year, 1 to < 5 years, 5 to < 10 years, 10 to < 15 years, or ≥ 15 years), BMI, albumin, blood urea nitrogen, creatinine, CRP, white blood cell count, hemoglobin, and platelet count as independent variables.
All analyses were performed using SPSS Statistics version 21 (IBM SPSS Statistics for Windows, IBM, Armonk, NY), and p < 0.05 was considered to be statistically significant. This study was approved by the Ethics Committee of the Japanese Society for Dialysis Therapy (authorization number: 1–8), and all procedures adhered to the Declaration of Helsinki.
