|Year : 2017 | Volume
| Issue : 4 | Page : 991-996
The value of lipocalin-2 as a predictive biomarker of bacterial infection in hepatic patients
Enas M Ghoniem1, Azza M Abd El Aziz1, Tawfik M Abd El-Motelb1, Ahmed A Aly Salama2, Hanaa M I. El Gazzar1
1 Department of Medical Microbiology and Immunology, National Liver Institute, Menoufia, Egypt
2 Department of Medical Microbiology and Immunology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
|Date of Submission||30-Apr-2016|
|Date of Acceptance||27-Jun-2016|
|Date of Web Publication||04-Apr-2018|
Hanaa M I. El Gazzar
Source of Support: None, Conflict of Interest: None
The aim of this study was to assess serum levels of lipocalin-2 in hepatic patients with bacterial infection and evaluate the role of lipocalin-2 as a diagnostic marker for bacterial infection.
Lipocalin-2 is a 25-kDa protein present in peroxidase-negative granules of neutrophils, colocalized with lactoferrin, and is released following neutrophil activation. Lipocalin-2 exerts bacteriostatic effects, which are explained by its ability to capture and deplete siderophores, small iron-binding molecules that are synthesized by certain bacteria as a means of iron acquisition.
Patients and methods
Eighty patients divided into three groups were included in the study: group 1 included 40 hepatic patients with bacterial infection; group 2 included 20 hepatic patients without bacterial infection; and group 3 included 20 healthy patients as the control group. Liver function tests, complete blood count, evaluation of serum level of C reactive protein, and serum measurement of lipocalin-2 were carried out in all groups.
Microbiological examination (blood, urine, sputum, and ascetic fluid cultures) was performed for patients.
Serum level of lipocalin-2 was significantly increased in hepatic patients with bacterial infection than in other groups (P ≤ 0.0001). Lipocalin-2 at cutoff less than 60 ng/ml could predict bacterial infection with 90% sensitivity and 72% specificity.
Lipocalin-2 is an excellent predictive biomarker of bacterial infection. It can be used as a diagnostic marker with better sensitivity and specificity than C reactive protein for the diagnosis of bacterial infection, especially in chronic liver disease.
Keywords: bacterial infection, chronic liver disease, lipocalin-2
|How to cite this article:|
Ghoniem EM, Abd El Aziz AM, Abd El-Motelb TM, Aly Salama AA, I. El Gazzar HM. The value of lipocalin-2 as a predictive biomarker of bacterial infection in hepatic patients. Menoufia Med J 2017;30:991-6
|How to cite this URL:|
Ghoniem EM, Abd El Aziz AM, Abd El-Motelb TM, Aly Salama AA, I. El Gazzar HM. The value of lipocalin-2 as a predictive biomarker of bacterial infection in hepatic patients. Menoufia Med J [serial online] 2017 [cited 2018 Jun 19];30:991-6. Available from: http://www.mmj.eg.net/text.asp?2017/30/4/991/229210
| Introduction|| |
Bacterial infection is a serious and often fatal complication in patients with liver disease. The consequences of infection include prolonged hospitalization, acute kidney injury, susceptibility to further infections, exclusion from liver transplant list, and death.
The magnitude of infections in liver disease is not quantifiable for many reasons. Infections are often difficult to recognize in patients with cirrhosis because 30–50% of infections, such as spontaneous bacterial peritonitis (SBP), can remain culture negative. Often, recognition of infection is rendered more difficult by the absence of normal clinical features of infection, such as fever, rigors, hypotension, and leukocytosis, in which case the only clues may be deterioration to hepatic state before coma, or coma, or renal failure.
Strategies such as measuring C-reactive protein (CRP) and procalcitonin may be helpful in selected patients, but a specific differentiator is still needed. Time-appropriate strategies are needed to suspect infections and send cultures early so as to initiate appropriate antimicrobial therapy.
Lipocalin-2, also known as neutrophil gelatinase-associated lipocalin, is a 25-kDa protein belonging to the lipocalin superfamily.
Lipocalin-2, an essential component of the antimicrobial innate immune system, is present in neutrophils and multiple other tissues. It prevents iron acquisition by microorganisms by sequestering iron-loaded bacterial siderophores. Lipocalin-2 also modulates neutrophil functions. Its production is inducible following Toll-like receptor 4 activation and release of proinflammatory cytokines. Elevated levels of lipocalin-2 have been detected in the blood of patients with bacterial urinary tract infection (UTI), community-acquired pneumonia, sepsis, as well as in the cerebrospinal fluid and peritoneal fluid of patients with bacterial meningitis and peritonitis.
Lipocalin-2 exerts bacteriostatic effects, which are explained by its ability to capture and deplete siderophores, small iron-binding molecules that are synthesized by certain bacteria as a means of iron acquisition. Consistently, lipocalin-2 deficiency in genetically modified mice leads to an increased growth of bacteria.
The objective of this study was to assess serum levels of lipocalin-2 in hepatic patients with bacterial infection and evaluate the role of lipocalin-2 as a diagnostic marker for bacterial infection.
| Patients and Methods|| |
This study was carried out on 60 patients with chronic liver disease (38 men and 22 women), with a mean age of 45.89 ± 7.16 years, who were admitted to medical and surgical wards or were attending the outpatient clinics at National Liver Institute, Menoufia University, from November 2014 to September 2015. According to clinical data and microbiological cultures, they were classified into two groups: group 1 included 40 chronic hepatic patients with bacterial infection (28 men and 12 women) and group 2 included 20 chronic hepatic patients without bacterial infection (10 men and 10 women). The study also included 20 healthy individuals, age and sex matched, as a control group. Informed consent was obtained from all patients and this study was approved by the Ethical Committee of National Liver Institute, Menoufia University.
The studied patients were subjected to the following:
- Full history taking, thorough clinical examination, abdominal ultrasonography, and laboratory tests including complete blood count, liver function tests (alanine transaminase, aspartate transaminase, serum total and direct bilirubin, and serum albumin), and CRP
- Bacteriological cultures of blood using the BacT/ALERT System (bioMérieux, Inc., Durham, England), as well as cultures of urine, sputum, and ascetic fluid. Samples were inoculated onto nutrient, blood, MacConkey, and mannitol salt agar plates and incubated at 37°C for 24–48 h, and the growing organisms were identified by direct microscopic examination of Gram-stained smears and biochemical tests. In addition, the VITEK 2 (bioMérieux Marcy l'Etoile, Marcy l'Etoile, France) Compact System was used for identification of isolates.
- Quantitative determination of serum level of lipocalin-2 by enzyme-linked immunosorbent assay using Boster's human lipocalin-2 ELISA Kit (Biomatik Corporation, Cambridge, Ontario, Canada) (Cat. No. NSO, Q21-G198; USA).
Quantitative determination of serum level of lipocalin-2, CRP, and complete blood count was carried out for the control patients.
The data were collected, tabulated, and analyzed by SPSS (statistical package for the social sciences) for Windows (Version 17.0., Chicago, Illinois, USA). The c2 test was performed to study the association between two qualitative variables. The Student t-test is a test of significance used for comparison between two groups having normally distributed quantitative variables. For quantitative data, statistical significance among the groups was tested by means of the Kruskal–Wallis nonparametric test. When the Kruskal–Wallis test showed significance, significance between individual groups was tested by applying Tukey's post-hoc test, which is used for multiple comparisons of quantitative data among different groups. The Mann–Whitney U-test is a nonparametric test of significance used for comparison between two groups having non-normally distributed quantitative variables. Correlation analysis is a statistical process for estimating the relationships among variables.
| Results|| |
The demographic data of the studied groups showed that the mean age of hepatic patients with bacterial infection (group 1), that of hepatic patients without bacterial infection (group 2), and that of healthy controls was 53.13 ± 5.637, 52.04 ± 7.133, and 50.50 ± 8.719, respectively. As regards sex, 70% of patients in group 1 were male and 30% were female. In group 2, 50% were male and 50% were female. These differences were statistically nonsignificant (P > 0.05) [Table 1].
According to type of infections in group 1, bacteremia was the most common infection (70%), followed by UTI (32.5%) and chest infection (22.5%), whereas SBP was the least common type of infection (20%) [Table 2] and [Figure 1].
|Figure 1: Type of infections in group 1. SBP, spontaneous bacterial peritonitis.|
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Regarding the distribution of isolates according to type of specimen, the most commonly isolated organism was Staphylococcus aureus from blood (35%), S. aureus, Klebsiella spp., and E scherichia coli from urine (10% for each), Klebsiella spp. from sputum (15%), and E. coli from ascetic fluid (17.5%) [Table 3].
As regards the level of infection markers in the studied groups lipocalin-2 levels and CRP were significantly higher in hepatic patients with bacterial infection (group 1) than in hepatic patients without bacterial infection (group 2) and in the control group. Further, CRP was significantly higher in group 2 than in controls, whereas white blood cell (WBC) count was significantly higher in group 1 than in controls [Table 4].
|Table 4: Comparison between the levels of infection markers in the studied groups|
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Receiver operator characteristic curves for lipocalin-2 and CRP showed that lipocalin-2 at a cutoff value greater than 60 ng/ml had a sensitivity of 90% and specificity of 72% for the diagnosis of bacterial infection, whereas CRP level at a cutoff greater than 5.5 mg/l had a sensitivity of 82%, specificity of 70%, positive predictive value (PPV) of 73%, negative predictive value (NPV) of 80%, and accuracy of 76% for the diagnosis of bacterial infection [Table 5] and [Figure 2], [Figure 3].
|Table 5: Comparison between lipocalin-2 and C reactive protein in the diagnosis of infection using receiver operator characteristic curve|
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|Figure 2: Receiver operator characteristic (ROC) curves for lipocalin-2 in the diagnosis of infection.|
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|Figure 3: Receiver operator characteristic (ROC) curves for C reactive protein in the diagnosis of infection.|
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| Discussion|| |
Bacterial infection is a serious and often fatal complication in patients with liver disease and can prove fatal either directly or by precipitation of gastrointestinal bleeding, renal failure, or hepatic encephalopathy.
In the present study we found that there was no significant statistical difference between hepatic patients with and those without bacterial infection regarding age and sex. Nearly similar results were reported by Ximenes et al..
Regarding the type of infection, our study revealed that bacteremia was the most common infection (70%) followed by UTI (32.5%) and chest infection (22.5%), whereas SBP was the least common type of infection (20%).
Nearly similar results were reported by Preda et al. who found that the incidence of SPB was 43.3%, that of UTI was 33.3%, and that of pneumonia was 13.3% in cirrhotic patients with bacterial infections.
Preveden found that the most common infections were pneumonia (21.56%), UTI (20.91%), and SBP (18.95%). Localization of infection remained undetermined in 24.18% of hepatic patients.
Bajaj et al. found that the majority of infections were SBP and UTI, followed by spontaneous bacteremia, skin, and respiratory tract infection.
The current study revealed that the serum level of lipocalin-2 was significantly higher in hepatic patients with bacterial infection than in hepatic patients without bacterial infection and in controls.
These results coincide with those of Venge et al., Itenov et al., and Rafiei et al., who found that the level of liopcalin-2 was significantly higher in patients with bacterial infections than in the healthy group. Khosravi et al. found that lipocalin-2 levels were significantly higher in septic neonates compared with that in nonseptic neonates and Zhang et al. also reported that the serum level of lipocalin-2 was higher in hepatic patients with bacterial infection than in those without bacterial infection.
Further, in a study carried out on Egyptian children with chronic liver disease, Behairy et al. reported that the serum level of lipocalin-2 was significantly higher in patients with infection.
These findings prove the fact that lipocalin-2 is increased during bacterial infection as it is an essential component of the antimicrobial innate immune system. Lipocalin-2 is present in peroxidase-negative granules of neutrophils and is released following neutrophil activation. It has bacteriostatic function by binding and sequestration of bacterial siderophores, thus depriving bacteria of iron. It also promotes neutrophil adhesion and extravasation, acts as a chemoattractant for neutrophils, promotes phagocytosis and bacterial killing by neutrophils, and promotes neutrophil maturation. Moreover, there is in-vitro evidence that lipocalin-2 can link innate and adaptive immunity. Lipocalin-2 increases the expression of HLA-G (an HLA class I molecule involved in tolerance) on CD4+ T lymphocytes. Iron-bound lipocalin-2 also activates CD4+/FoxP3+ regulatory T lymphocytes, suggesting its possible involvement in modulating cell-mediated immunity.
Regarding the CRP level, the present study showed that the CRP level was significantly higher in hepatic patients with bacterial infection (group 1) than in hepatic patients without bacterial infection and in the control group.
In agreement, Li et al. and Ximenes et al. found that levels of CRP were significantly higher in cirrhotic patients with bacterial infection than in those without bacterial infection in their study of hepatic patients. Also Venge et al. found that the level of CRP was increased during bacterial infection compared with that in the healthy group.
Also in the current study we found that CRP was significantly higher in hepatic patients without bacterial infection (group 2) than in controls.
Similar results were reported by Campillo et al.. andPieri et al., who found that CRP concentrations were higher in noninfected patients with cirrhosis than in controls.
The explanation for increasing CRP level in noninfected hepatic patients compared with controls is that CRP level increases in the presence of acute or chronic inflammation. In patients with cirrhosis, the CRP basal level is higher than in patients without cirrhosis, because of chronic hepatic inflammation, but when infection occurs the more severe the underlying liver dysfunction, the lower the increase in CRP. Therefore, the predictive power of CRP for infection and prognosis is weak in patients with decompensated/advanced cirrhosis.
In our study WBC count was significantly higher in patients with bacterial infection (group 1) compared with other groups.
Nearly similar results were detected by Li et al., who found that there was leukocytosis in the sepsis group. Venge et al. also found that WBC count was significantly higher in the infected group.
According to receiver operator characteristic curve analysis, the current study showed that lipocalin-2 level at a cutoff greater than 60 ng/ml had a sensitivity of 90%, specificity of 72%, PPV of 77%, NPV of 88%, and accuracy of 81% in the diagnosis of bacterial infection, whereas CRP level at a cutoff greater than 5.5 had a sensitivity of 82%, specificity of 70%, PPV of 73%, NPV of 80%, and accuracy of 76%.
Nearly similar results were reported by Ximenes et al., who found that lipocalin-2 level at a cutoff greater than 68 ng/mg had a sensitivity of 80%, specificity of 75%, PPV of 80%, and NPV of 75%. Zhang et al. also reported nearly similar results: at a cutoff value of 158 ng/ml, lipocalin-2 had a sensitivity of 83.3% and specificity of 92.6%. Khosravi et al. found that serum lipocalin-2 at a cutoff of 48 ng/ml could potentially detect neonates with sepsis with a sensitivity and specificity of 92 and 91%, respectively.
Safdar and Shalaby found that the optimal cutoff value for CRP was 6.9 mg/l, with sensitivity 53% and specificity 47%, and Behairy et al. reported that CRP at cutoff of 18 mg/l had 75% sensitivity and 76% specificity in the diagnosis of bacterial infection.
| Conclusion|| |
Lipocalin-2 is an excellent predictive biomarker of bacterial infection. The basal level of CRP is high in patients with chronic liver diseases so the predictive power of CRP for infection and prognosis is weak in patients with advanced liver disease. Lipocalin-2 can be used as a diagnostic marker with better sensitivity and specificity than CRP for the diagnosis of infection, especially in chronic liver disease.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]