A total of 1023 patients with sepsis participated in the study; however, 22 patients were lost during follow-up and were excluded from the study. Therefore, 1001 patients were included in the study; The median age of enrollment was 73 (IQR 61-83) years; 64.2% of patients were male. A total of 117 patients died within 28 days. PCT, DDi and lactate levels were significantly higher in the survivor group, compared to the non-survivor group (PCT median 1.5 ng/ L vs. 24.2 ng/ L; DDi median 1.8 μmol/ L vs. 5.9 μmol/ L; lactate median 1.6 mmol/ L vs. 5.6 mmol/ L, all p＜0.01). The survival group had lower APACHE Ⅱ (median 14 vs. 25, p＜0.01) and SOFA (median 3 vs. 11, p＜0.01) scores compared to the mortality group and lower rate of MV, AICU, VD and CRRT (19.2% vs. 94.0%, 35.9% vs. 97.4%, 10.2% vs. 88.0%, 6.2%vs. 61.2% respectively). Detailed data are shown in Table 1.
Calculation of the PDLS
According to the cut-off value determined by ROC curve analysis, PCT, DDI, and lactate were divided into two groups. Therefore, the recommended cut-off values for PCT (8.12ng/ L), DDi (3.59μmol/ L), and Lactate (2.65mmol/ L) are based on the maximum of Youden's index was used to calculate PDLS. The method of calculating PDLS is shown in Table 2.
PDLS and the severity of sepsis
According to PDLS, the clinical characteristics of sepsis patients are shown in Table 3. Heart rates and respiratory rates, temperature, WBC, BUN, and creatinine significantly increased with an increase in PDLS. Conversely, diastolic blood pressure (DBP), systolic blood pressure (SBP), PH, partial pressure of oxygen (PO2), Platelet, albumin significantly decreased with increasing PDLS.
Patients with sepsis having higher PDLS also had higher sofa and APACHE II scores than those with lower PDLS. For patients with PDLS of 0, 1, 2, and 3, the median APACHEII scores were 13 (IQR 9-18), 17 (IQR 12-23), 20 (IQR 13-28), and 25 (IQR 20-30), respectively (P < 0.01). The median SOFA scores were 3 (IQR 2-4), 4 (IQR 3-6), 6 (IQR 4-11) and 11 (IQR 7-15) (P < 0.01), respectively. With the increase of PDLS, the 28-day mortality, MV, AICU, VD and CRRT rates increased gradually. The 28-day mortality rate of patients with scores of 0, 1, 2 and 3 were 0.2%, 2.4%, 18.0%, and 92.2%, respectively (p < 0.01); MV were 11.3%, 30.2%, 51.7% and 93.1%, respectively(p < 0.01); AICU were 25.6%, 48%, 75.3% and 98.0%, respectively(p < 0.01); VD were 4.3%, 16.3%, 46.1% and 85.3%, respectively(p < 0.01); CRRT were 2.9%, 8.7%, 29.2% and 61.8%, respectively (p < 0.01) ( Table 3).
PDLS is an independent prognostic factor in patients with sepsis
Univariate logistic regression model revealed that PDLS was positively correlated with the risk of mortality, MV, VD, and AICU. After adjusting for these potential confounders in the multivariate logistic regression analysis, the PDLS was independently associated with 28-day mortality (OR=21.60, 95% CI =11.02-42.34, p< 0.01), MV(OR=2.88, 95% CI =2.20-3.77, p< 0.01), AICU (OR=2.49, 95% CI =1.99-3.11, p< 0.01), VD (OR=2.89, 95% CI =2.22-3.75, p< 0.01) and CRRT(OR=1.91, 95% CI =1.44-2.54, p< 0.01) (Table 4).
Comparison of PDLS to SOFA and APACHE II scores
The differentiation of 28-day mortality as assessed by AUROC (Figure 2; Table 5) indicates that PDLS (AUROC, 0.96) was significantly higher than SOFA (AUROC, 0.84) and APACHE II (AUROC, 0.84). Next, we selected the critical values of PDLS, SOFA and APACHE II with high sensitivity and specificity in predicting 28-day mortality by ROC curve analysis. The sensitivities, specificities, positive/negative predictive values and positive/negative likelihood ratios (LR+/−) of PDLS, SOFA and APACHE Ⅱ for mortality are shown in Table 5.