Demographics and baseline qSOFA and SIRS scores in survivals and nonsurvivals
Of 370 suspected SFTS patients who were admitted to our hospital from May 2013 to July 2017, 321 were confirmed by detected positive SFTSV and were included in this study. Mean age of all included patients was 63.8±11.2 years. And 87 patients (27.1%) died during hospitalization who were older than those who survived (70.6±9.2 vs 61.3±10.8 years, p<0.0001). Percentage of male patients in nonsurvivors was greater than in survivors (p<0.05). Proportions of patients with qSOFA and SIRS score >2 were dramatically increased in nonsurvivors compared with survivors (p<0.0001). Hospital stays and biochemical parameters had significant differences between the two groups. Data are shown in Table 1 and Figure 1.
Predictive values of independent risk factors, baseline qSOFA and SIRS scores and established risk score models for in-hospitsl mortality of SFTS patients
Predictive values of independent risk factors and risk models for all patients
Multivariate logistic regression analysis showed that age, AST, qSOFA and SIRS scores were the independent risk factors for in-hospitsl mortality of all SFTS patients. AUCs (95% CI) , cutoff values, SEN, SPE, PPV and NPV of these factors for the prediction of in-hospitsl mortality are included in Table 2. Based on values and regression coefficient of these risk factors, a risk score model was constructed as M1=0.102×AGE+0.002×AST+1.296×qSOFA score+0.486×SIRS score. AUC (95% CI) of M1 was 0.919 (0.883-0.946) with odd ratio (OR) (95% CI)=2.95 (2.308-3.771) at the cutoff value of 10.272 (Figure 2A). Patients with M1 value > 9.22 were at high-risk of mortality. Kaplan-Meier survival analysis showed a strong difference between high-risk and low-risk groups (log-rank test, c2 = 126.3, p<0.0001) (Figure 3A).
Considering the unavailability of AST at the immediate admission of suspected SFTS and its relative small regression coefficient. We modified the model into a simpler one as M1’= 0.102×AGE+1.296×qSOFA score+0.486×SIRS score. AUCs (95% CI) of M1’ was 0.894 (0.855-0.925) with OR (95% CI)=3.144 (2.319-4.263) at the cutoff value of >8.034 (Figure 2B). LR+ value of M1’ is 24.2 which is superior to 15.3 of M1. Survival analysis demonstrated a strong statistical significance between high and low-risk groups (log-rank test, c2 = 154.5, p<0.0001) (Figure 3B).
Predictive values of independent risk factors and risk models for patients with age ≥60 years
M1 and M1’ also have high predictive values for in-hospital mortality in those patients at age ≥60 years (Table 2, Figure 2C, 2D). LR+ value of M1’ is also superior to that of M1 in this cohort. Data are summarized in Table 2. Log-rank c2 of M1 and M1’were 149.7 and 114.3, respectively in survival analysis (p<0.0001) (Figure 3C, 3D). Logistic regression analysis indicated that age, plasma lactate, serum AST and hs-CRP levels, and qSOFA and SIRS scores were independent risk factors for in-hospitsl mortality admitted in ICU. Based on these factors, we established another risk score model:
M2=0.127×AGE+0.953×lactate+0.002×AST+0.056×Hs-CRP+0.86×qSOFA+0.866×SIRS.
This model also has high predictive value for in-hospital mortality in this group of patients (Table 2, Figure 2E). Survival analysis showed a marked statistical significance between high and low-risk groups (log-rank test, c2 = 112.7, p<0.0001) (Figure 3E).
Predictive values of independent risk factors and risk models for patients in ICU
M1 and M1’ also have relative low predictive values for in-hospital mortality in those patients enrolled in ICU (Table 2, Figure 2F for M1’). Survival analysis displayed a significant difference between high and low-risk groups (log-rank test, M1:c2 = 27.05, M1:c2 = 35.5, p<0.0001)
Logistic regression analysis demonstrated d that qSOFA score was the sole independent risk factor for mortality of patients enrolled in ICU at admission or transferred to. And the predictive value of qSOFA score was moderate (Table 2). Log-rank c2 = 26.61 (p<0.0001) in survival analysis. SEN, SPE, PPV, NPV, LR+ and LR- of all parameters are summarized in Table 2.