CAP is an acute pulmonary infection caused by a variety of pathogens. Its immunopathology is characterized by an acute lower respiratory inflammatory response regulated by cytokines or other inflammatory mediators[13]. CAP is currently recognized as one of the major public health problems. It has been identified as the third most common cause of death worldwide, with high morbidity and mortality. The annual incidence of CAP in the elderly has been reported to be 0.33%–4.6%[14,15]. sCAP is induced by the aggravated inflammatory reaction in the lung tissue and has high morbidity and mortality[3,16]. Therefore, timely and effective assessment of the condition of CAP patients and the formulation of a reasonable and effective diagnosis and treatment plan is very important.
In this study, the levels of HBP and HBP–ALB in patients with CAP were compared with those of the patients with other inflammatory markers (WBC, CRP, and PCT). The patients with sCAP were older and had a higher average age than those of the patients with mCAP. In addition, the WBC (10.78), PCT (0.355), HBP (140.68), creatinine (116), and D-dimer (3.52) count of patients with sCAP were higher than those of the patients with mCAP. The level of ALB of patients with sCAP was lower than that of the patients with mCAP. CRP increases in all infections, stress reactions, and tumor diseases. However, this study found that the concentration of CRP in patients with mCAP was not significantly different from that in patients with sCAP. This result is consistent with that reported by Chen[7].
PCT, secreted by parathyroid C cells, comprises 116 amino acids and can be detected 2 h after infection[17]. Studies have shown that PCT has a good diagnostic value in predicting the severity and prognosis of CAP. HBP, also known as azuroxine or cationic 37 kDa antibacterial protein (CAP37), is a multifunctional immunomodulatory protein[18]. It has extensive antibacterial activity. In addition, it shows chemotaxis and can activate monocytes and macrophages. It can also increase the vascular permeability, which plays an important role in the prediction of infectious diseases. HBP is an important player in the pathophysiology of organ dysfunction induced by sepsis[9]. Huang demonstrated that the level of plasma HBP significantly increased in children with sCAP on admission, and that HBP may be a better predictor of disease progression in children with sCAP than routine biomarkers[13]. In this study, the AUC for HBP for predicting the sCAP was 0.776. Patients with sCAP were predicted to have more WBCs than the average number (area under ROC curve: 0.674) and PCT (area under ROC curve: 0.677), which was similar to that reported by Cai[19]. ALB is the main protein of the human plasma and is synthesized by the liver, which plays an important role in the inflammatory response and oxidative stress. The synthesis of ALB significantly decreased in the acute phase of the inflammatory reaction. Release of inflammatory mediators and chemokines increases the permeability of the cell membrane, resulting in ALB loss through its leakage from capillaries[20,21]. Lee et al demonstrated that ALB is an independent risk factor in 28-day mortality in patients with CAP, with an RR of 0.37[22]. Mehul et al conducted a prospective study and showed that the ratio of blood urea nitrogen to ALB is an independent risk factor for poor prognosis in CAP[23].
This study is a retrospective analysis of the clinical data of 91 patients with CAP, which showed that HBP–ALB is highly valuable in the assessment of CAP severity (area under ROC curve: 0.805). In fact, HBP–ALB has a higher predictive value than that of HBP alone (area under ROC curve: 0.776). Both HBP and ALB can be obtained directly from laboratory indicators without conducting any further calculation. It also helps avoid any increase in the financial burden of patients.
In conclusion, HBP combined with ALB at admission can predict the severity of CAP. Clinicians can evaluate the severity of CAP based on the level of HBP–ALB and then make an appropriate diagnosis and come up with a suitable treatment plan.