The mortality rate of elderly patients with Coronavirus Disease 2019 (COVID-19) was significantly higher than the overall mortality rate. However, besides age, leading death risk factors for the high mortality in elderly patients remain unidentified. This retrospective study included 210 elderly COVID-19 patients (aged ≥ 65 years), of whom 175 patients were discharged and 35 died. All deceased patients had at least one comorbidity. A significantly higher proportion of patients in the deceased group had cardiovascular diseases (49% vs. 20%), respiratory diseases (51% vs. 11%), chronic kidney disease (29% vs. 5%) and cerebrovascular disease (20% vs. 3%) than that in the discharged group. The median levels of C-reactive protein (125.8mg/L vs. 9.3mg/L) and blood urea nitrogen (7.2mmol/L vs. 4.4mmol/L) were significantly higher and median lymphocyte counts (0.7×10 9 /L vs. 1.1×10 9 /L) significantly lower in the deceased group than those in the discharged group. The survival curve analysis showed that higher C-reactive protein (≥5mg/L) plus any other abnormalities of lymphocyte, blood urea nitrogen or lactate dehydrogenase significantly predicted poor prognosis of COVID-19 infected elderly patients. This study revealed that the risk factors for the death in these elderly patients included comorbidities, increased levels of C-reactive protein and blood urea nitrogen, and lymphopenia during hospitalization.

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In order to obtain accurate results of volatile fatty acids (VFAs) in rumen fluid by capillary gas chromatography (GC), a pretreatment method was firstly conducted by dissolving VFAs in the methanol. An internal standard method (ISM) with crotonic acid as the internal standard was adopted in the detection. The results showed that the reproducibility of VFA (acetic acid, propanoic acid and butyric acid) was enhanced remarkably with methanol added as the solvent. The reproducibility was dependent on both of the VFA concentration and methanol amount. In conclusion, methanol solvent was more suitable than aqueous solvent for VFA accurate detection with ISM by capillary GC.