3.1 Comparison of clinical characteristics
A total of 842 patients diagnosed with AP from 2013 to 2018 were reviewed in this study, 582 patients were excluded according to the exclusion criteria, and finally 260 AP patients were enrolled. Of them, 176 (67.7%) patients had normal serum HBDH levels, whereas 84 patients (32.3%) had elevated serum HBDH levels.
Of all 260 patients, 162 patients（62.3%）were male, and the average age was 51.7 years old. Hypertriglyceridemia was the most common AP etiology (40.4%), followed by biliary diseases (24.2%) and alcohol consumption (14.2%), and other causes accounted for 21.2% of cases. Among these patients, 81 (31.2%) patients suffered from organ failure, and 75 (28.8%) had SIRS, as showed in Table 1.
3.2 Serum HBDH levels and severity of AP
There was no significant difference in terms of age, gender, history of tobacco and alcohol consumption, and underling disease between the n-HBDH and h-HBDH groups. Compared with the n-HBDH group, the incidence of MAP was lower (47.6% vs. 79.0%), whereas the incidence of SAP (14.3% vs. 2.3%) and MSAP (38.1% vs. 18.8%) were higher in the h-HBDH group (both P＜0.001). Moreover, there was a higher proportion of organ failure (52.4% vs. 21.0%) and SIRS (46.4% vs. 20.5%) in the h-HBDH group, as shown in Table 1(both P < 0.001). In addition, in the h-HBDH group, patients had higher levels of WBC, percentage of neutrophils (N%), LDH, DB, AST, ALT, γ-GGT, BUN, CRP and Ca2+ (all P < 0.05). Whereas, there was no significant difference in the serum levels of Cr between the two groups, as shown in Table 2.
3.3 Serum HBDH levels and clinical scoring systems in AP
The scoring systems for the severity of AP are varied and each has its own emphasis. We observed correlation between serum HBDH levels and clinical scoring systems. As shown in Figure 1, serum HBDH levels were significantly related to the clinical scoring systems of AP. Serum HBDH levels were significantly increased in patients with organ failure and SIRS, and were positively correlated with Atlanta classification, Ranson score, and BISAP score. Of the 260 AP patients with elevated HBDH levels, 110 patients had their HBDH levels re-measured during hospitalisation, which significantly decreased from 191.5 ± 7.459 U/L to 163.6 ± 5.053 U/L (Figure 2).
3.4 Correlation between serum HBDH levels and other clinical indicators
To further evaluate the predictive value of HBDH level for AP prognosis, correlation analysis was carried out between the serum HBDH level and other clinical markers (all of these data are from the same time). As shown in Table 3, serum HBDH levels were positively correlated with the serum levels of WBC (R = 0.273; P < 0.001), N% (R = 0.162; P = 0.009), LDH (R = 0.467; P < 0.001), AST (R = 0.152; P = 0.014), GGT (R = 0.150; P = 0.015), BUN (R = 0.165; P = 0.008), TG (R = 0.195; P = 0.002), CHO (R = 0.132; P = 0.037), GLU (R = 0.171; P = 0.006), CRP (R = 0.182; P = 0.003). Whereas, there was no significant correlation between serum HBDH and Ca2+, ALT, CRP, DB, HDL and LDL.
3.5 ROC curve analysis of HBDH to diagnose organ failure
ROC curve analysis was performed to determine the cutoff value of HBDH for predicting AP with persistent organ failure or SIRS. As shown in Figure 3, the results revealed that the area under the ROC curve of HBDH for persistent organ failure was 0.778 and the optimal cutoff level was 195.0 U/L, which provided a 75.0% sensitivity and a 74.6% specificity. The area under the ROC curve of HBDH for SIRS was 0.724 and the optimal clinical cutoff level was 166.5 U/L, which provided a 66.7% sensitivity and a 68.4% specificity. In addition, our study found that the ability of serum HBDH for predicting persistent organ failure or SIRS is superior to LDH and CRP.