There were six previously identified coronaviruses that infected humans, four of which were more common and less pathogenic in humans. The other two were known as SARS-coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), which caused severe respiratory diseases. The mortality of SARS has been reported as more than 10% and MERS at more than 35% [8, 9]. The SARS-CoV-2 was known as the seventh human coronavirus. The case fatality rate among hospitalized COVID-19 patients was reported to be 4.3–15% [5, 10,11,12,13], while the case fatality rate of COVID-19 in maintenance hemodialysis patients was 25–41% [14,15,16]. Our study showed that the case fatality rate of COVID-19 in maintenance hemodialysis patients was 19.1%. The mortality rate was much higher than that observed in the general population. Therefore, it is crucial to identify specific serological indicators for treatment decisions.
In terms of laboratory tests, the main characteristics of COVID-19 in maintenance hemodialysis patients were normal white blood cell count, normal neutrophil count, normal platelet count, decreased lymphocyte count, decreased albumin, increased CRP, increased procalcitonin, and increased LDH and D-dimer. For those who died, the white blood cell count, neutrophil count, CRP, procalcitonin, and LDH were all significantly higher than that in the survival group, but the albumin was lower than that in the survival group. Elevated CRP and procalcitonin may indicate a secondary bacterial infection in the clinical course of hemodialysis patients with COVID-19. Low albumin and high LDH suggested poor prognosis for COVID-19 in hemodialysis patients, as well as COVID-19 patients without hemodialysis [17].
Our study showed an association between laboratory parameters on admission and poor outcome for COVID-19 in hemodialysis patients. We found that white blood cell count, neutrophil count, albumin, CRP, procalcitonin, and LDH were all associated with the prognosis of COVID-19 in maintenance hemodialysis patients. Previous studies suggested that lymphopenia were a predictor of prognosis in COVID-19 patients [18]. However, our study showed no association between lymphopenia and prognosis of COVID-19 in maintenance hemodialysis patients. The reason may be that hemodialysis patients exist peripheral blood lymphopenia, which is accompanied by decreased lymphocyte proliferative response when stimulated by different antigens [19].
In this study, the ROC curve was used to analyze the prognostic value of laboratory indicators. The AUC of white blood cell count, neutrophil count, albumin, CRP, procalcitonin, and LDH ranged from 0.728 to 0.895. The AUC of CRP was the largest. The optimal working point was 45.2 mg/L, and the sensitivity and specificity to predict the prognosis of maintenance hemodialysis patients infected with COVID-19 were 88.9% and 68.4%, respectively. CRP is a useful inflammatory marker and indicator that plays an important role in host resistance to invasive pathogens and inflammation [20]. CRP is highly correlated with acute lung injury in 2019-nCoV-infected patients [21]. Besides, higher CRP has been linked to unfavorable aspects of COVID-19 diseases, such as cardiac injury, and acute respiratory distress syndrome development, and fatality [22,23,24]. Therefore, the detection of CRP levels in COVID-19 with maintenance hemodialysis patients is of great value in assessing the severity of their condition.
Several limitations of this study should be acknowledged. First, our study was a single-center retrospective study and some patients were clinically diagnosed with COVID-19, which may affect the generalization of the results due to the limitation of enrolled patients. Second, some important laboratory results were incomplete. Finally, we did not conduct logistic regression analysis due to the small sample size, therefore, we cannot evaluate the effect of other clinical indicators other than laboratory parameters, especially age, on the results.