Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a new coronavirus that is affecting the entire global population.1 The clinical presentation varies widely, from asymptomatic to severe respiratory distress requiring mechanical ventilation and admission to an Intensive Care Unit (ICU).2 Severe cases are associated with clotting disorders, thromboembolic complications and a systemic inflammation that can lead to multiple organ dysfunction.3,4

In spite of global measures and lockdowns, on 25 May 2020 the incidence of coronavirus disease 2019 (COVID-19) was still rising, with 5,304,772 laboratory-confirmed cases and more than 342,029 deaths worldwide according to the World Health Organisation. The Spanish Ministry of Health had reported 235,000 confirmed COVID-19 cases in Spain and, according to the Coronavirus Resource Centre of Johns Hopkins University, the incidence in Madrid was 1,021.90 cases per 100,000 inhabitants.

SARS-CoV-2 infection affected more frequently to elderly people with comorbidities, and most studies have focused on populations with chronic obstructive pulmonary disease, hypertension or obesity.5 Patients with chronic kidney disease are a vulnerable population, especially those in end-stage renal disease on dialysis. These patients often have many factors associated with increased risk, such as cardiovascular disease, advanced age, intrinsic frailty and an weakened immune system―.6–8 There is little data on the incidence and course of COVID-19 in dialysis patients. Two recent studies in patients treated with in-centre haemodialysis (HD) found different incidences (2.5% in Wuhan9 and 18.8% in Spain10), but there are no data in the home dialysis population. Home dialysis may imply a protective factor as the repeated contact that occurs with in-centre haemodialysis can be avoided.

The aim of this study is to describe the incidence of COVID-19 in a Home Dialysis Unit (HDU) in Madrid, one of the worst-hit areas in Europe, and to assess its course in this group of patients compared with our in-centre dialysis patients.

We analysed a total of 57 peritoneal dialysis (PD) patients and 22 home haemodialysis (HHD) patients treated in our HDU. Twelve (15.1%) were diagnosed with COVID-19: nine (15.7%) were on PD and three (13.6%) were on HHD. The characteristics of patients with and without COVID-19 are shown in Table 1.

All patients but one were diagnosed as positive for SARS-CoV-2 using the RT-PCR test; the other patient was diagnosed based on clinical, analytical and radiological data. The mean time from onset of symptoms to RT-PCR diagnosis was 7.2 ± 5.7 days (range 0–18). Eleven patient (91.6%) were hospitalised; the patient who did not require hospitalisation was the only one who did not present pneumonia. Two patients were diagnosed during a hospital admission for other reasons (at 3 and 36 days respectively), (nosocomial transmission, 17%).

The mean age of the patients was 62 ± 18.5 years (range 27–82); 75% were male, all had hypertension and 33.3% had diabetes. Underlying comorbidities are shown in Table 2. With regard to chronic treatments, 10 patients (83.3%) were using renin-angiotensin-aldosterone system inhibitors, two (16.7%) immunosuppressant treatment and three (25%) anticoagulant treatment.

This study reports COVID-19 incidence and outcomes in an HDU located in one of the most affected areas in Europe. It is difficult to calculate the worldwide incidence of COVID-19 infection in the general population, but on 25 May 2020 there were 10 cases for every 1000 inhabitants in the Madrid region.11 Our cohort includes 12 patients diagnosed with COVID-19, with an overall incidence of 15.1%: nine were on PD (15.7%) and three on HHD (13.6%). There are no pre-existing data on COVID-19 incidence and outcomes in home dialysis patients. Only one study, from Columbia University Irving Medical Center, described 59 COVID-19 patients, two of whom were being treated with PD.12 Several studies have shown the COVID-19 incidence in HD patients, with differing results. A study in Brescia (Italy) reported 21 patients with COVID-19 out of 400 in-centre HD patients, with an incidence of 5.2%,1 while another Italian study found an incidence of 16%.13 Another report, from Wuhan (China), observed an incidence of 16%,14 while a Spanish study in Madrid shows an incidence of 12.7%.2 In our registry of 199 in-centre HD patients, the incidence has been 16.6% (33 patients) during the same period. Several studies report the potential benefit of home dialysis for COVID-19 prevention, as patients may be safer at home, without the need for regular hospital visits.6,15–18 In our area, however, the incidence was similar between home dialysis and in-centre HD patients. These findings may be linked to the high proportion of the population affected in our geographic area. Moreover, community transmission predominated in our HDU.

The mean age of our patients with COVID-19 was similar to our hospital's cohort,19 but less than that reported in other HD patients.15 The mean age of our in-centre HD cohort with covid was 65.52 ± 17.9 years. The most common symptoms on admission were fever and cough. These manifestations have also been described as the most common in other studies20 and were also the most common in our in-centre haemodialysis cohort. Two patients were treated in the Emergency Department for chest pain, one of whom had high troponin levels. There are studies that report acute cardiac injury in severe cases of COVID-19 infection.21 In a study conducted in Wuhan (China), five of the first 41 patients with COVID-19 presented myocardial injury with troponin elevation, and their main complaint was cardiac symptoms rather than fever or cough.22 In our cohort, most patients (83%) had bilateral opacities in imaging, similar to those described by Goicoechea et al. in in-centre HD patients.2

Two patients died during follow-up, with an overall COVID-19 mortality rate of 16.6% (PD 22%; HHD 0%). In the general population, the estimated mortality varies between 1.4% and 8%.2 One of the largest COVID-19 case series reported in China found an overall mortality rate of 2.3%23; however, in a study conducted in the New York City area, the mortality rate was 21%.24 In Madrid, the overall mortality rate was 21% up to 25 May11 and 20.7% in our hospital cohort,19 which is higher than that observed in our home dialysis patients. Studies of the HD population have shown greater mortality than in the general population. In Brescia, a mortality rate of 29% has been reported.25 Two Spanish studies with in-centre HD patients found different mortality rates. Albalate et al. reported an overall mortality of 16.2%,10 whereas Goicoechea et al. reported 30.5%.2 A study at Columbia University which included two PD patients had a mortality rate of 31%, but the two PD patients survived.12 In our in-centre HD cohort, mortality was 27.3%. Most studies support the fact that COVID-19 mortality is higher in patients with associated conditions/comorbidities.5 In our cohort, the two patients who died were the oldest, as in the Columbia University study.12 Moreover, both were infected via nosocomial transmission, which indicates that their health status was probably worse than the other affected patients.

Comparison of the clinical characteristics and outcome of patients diagnosed with COVID-19 from our HDU and our in-centre HD cohort are summarised in Table 4. COVID-19 from our HDU had lower frequency of pneumonia, less need for oxygen therapy, lower frequency of lymphopaenia (72.7% vs. 100%) and less need for admission in in-centre HD. By contrast, the overall mortality of the 79 patients in our HDU (2.5%), this is lower than the overall morality of the 199 patients in our in-centre HD cohort (4.5%). A reason to explain this difference could be the epidemiological monitoring protocols used in in-centre HD patients, which could favour early diagnosis and admission of the patients at a less advanced stage of the infection. However due to the limited number of patients in the home dialysis group, it is prudent not to draw any conclusions based on these differences.

To our knowledge, this is the first report describing COVID-19 incidence and outcomes in home dialysis patients. These results come from a region with a high incidence of COVID-19 and may not be representative of other areas. All patients had been discharged from hospital when the results were analysed. Nevertheless, our study has a number of limitations. Firstly, the report does not include asymptomatic patients; only those who attended the Emergency Department and the general incidence may have been higher. Secondly, risk factors for mortality could not be analysed due to the low mortality rate observed. Thirdly, due to its retrospective design, some laboratory tests, such as interleukin-6, were not performed in all patients.

In conclusion, the incidence of COVID-19 infection in our home dialysis unit in Madrid during the peak of the pandemic was high, especially in PD patients. The majority of patients required hospitalisation. Advanced age and nosocomial transmission were the main factors linked to a poor prognosis.

The authors declare that they have no conflicts of interest.