Comparison of clinicopathologic characteristics among patients with HBV-positive, HCV-positive and Non-B Non-C hepatocellular carcinoma after hepatectomy: a systematic review and meta-analysis.

BACKGROUND: The incidence of HBV-negative and HCV-negative hepatocellular carcinoma (NBNC-HCC) is significantly increasing. However, their clinicopathologic features and prognosis remain elucidated. Our study aimed to compare the clinicopathologic characteristics and survival outcomes of NBNC-HCC with hepatitis virus-related HCC. METHOD: A literature review was performed in several databases, including PubMed, Embase, Cochrane Library and Web of Science, to identify the studies comparing NBNC-HCC with HBV-positive HCV-negative HCC (B-HCC), HBV-negative HCV-positive (C-HCC) and/or HBV-positive HCV-positive HCC (BC-HCC). The clinicopathologic characteristics and survival outcomes were extracted and pooled to access the difference. RESULTS: Thirty-two studies with 26,297 patients were included: 5390 patients in NBNC-HCC group, 9873 patients in B-HCC group, 10,848 patients in C-HCC group and 186 patients in BC-HCC group. Patients in NBNC-HCC group were more liable to be diagnosed at higher ages, but with better liver functions and lighter liver cirrhosis. Comparing to B-HCC and C-HCC groups, although NBNC-HCC group was prone to have larger tumor sizes, it did not have more advanced tumors. Meanwhile, there were no significant differences in both 5-year and 10-year disease-free survival and overall survival between NBNC-HCC group and B-HCC or C-HCC group. CONCLUSIONS: Our meta-analysis revealed patients with NBNC-HCC had as worse prognosis as those with hepatitis virus-related HCC. More attention should be paid on patients with non-alcoholic steatohepatitis or metabolic syndromes to prevent the incidence of NBNC-HCC.

Comparative study on left-sided versus right-sided hepatectomy for resectable peri-hilar cholangiocarcinoma: a systematic review and meta-analysis.

BACKGROUND: Peri-hilar cholangiocarcinoma (pCCA) is a unique entity, and radical surgery provides the only chance for cure and long-term survival. But it is still under debate which surgical strategy (i.e., left-sided hepatectomy, LH or right-sided hepatectomy, RH) should be followed and benefitted. METHODS: We performed a systematic review and meta-analysis to analyze the clinical outcomes and prognostic value of LH versus RH for resectable pCCA. This study followed the PRISMA and AMSTAR guidelines. RESULTS: A total of 14 cohort studies include 1072 patients in the meta-analysis. The results showed no statistical difference between the two groups in terms of overall survival (OS) and disease-free survival (DFS). But compared to the LH group, the RH group exhibited more employment of preoperative portal vein embolization (PVE), higher rate of overall complications, post-hepatectomy liver failure (PHLF), and perioperative mortality, while LH was associated with higher frequency of arterial resection/reconstruction, longer operative time, and more postoperative bile leakage. There was no statistical difference between the two groups in terms of preoperative biliary drainage, R0 resection rate, portal vein resection, intraoperative bleeding, and intraoperative blood transfusion rate. CONCLUSIONS: According to our meta-analyses, LH and RH have comparable oncological effects on curative resection for pCCA patients. Although LH is not inferior to RH in DFS and OS, it requires more arterial reconstruction which is technically demanding and should be performed by experienced surgeons in high-volume centers. Selectin of surgical strategy between LH and RH should be based on not only tumor location (Bismuth classification) but also vascular involvement and future liver remnant (FLR).

Guidelines for Diagnosis and Treatment of Hepatocellular Carcinoma with Portal Vein Tumor Thrombus in China (2021 Edition).

Portal vein tumor thrombus (PVTT) is very common and it plays a major role in the prognosis and clinical staging of hepatocellular carcinoma (HCC). We have published the first version of the guideline in 2016 and revised in 2018. Over the past several years, many new evidences for the treatment of PVTT become available, especially for the advent of new targeted drugs and immune checkpoint inhibitors which have further improved the prognosis of PVTT. So, the Chinese Association of Liver Cancer and Chinese Medical Doctor Association revised the 2018 version of the guideline to adapt to the development of PVTT treatment. Future treatment strategies for HCC with PVTT in China would depend on new evidences from more future clinical trials.

Retraction notice to "Iron chelator-induced up-regulation of Ndrg1 inhibits proliferation and EMT process by targeting Wnt/ß-catenin pathway in colon cancer cells" [Biochem. Biophys. Res. Commun. 506/1 (2018) 114-121].

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). The Editor-in-Chief has decided to retract this paper as the results cannot be relied upon. The authors contacted the editorial office admitting to outsourcing some of the experiments, specifically identifying that the Western Blot images were generated by a third-party laboratory. The authors tried to validate the results of the paper and obtain the raw data but were unable to do so, and offered to run additional experiments to correct the paper. The authors claim that the results and conclusions are still valid. The authors utilised potentially fraudulent data to generate their conclusions in this paper, which is in significant violation of journal policies and scientific best practice. The paper is therefore retracted.

The efficacy and safety of preoperative cholangiography via percutaneous transhepatic gallbladder drainage (PTGBD) for difficult laparoscopic cholecystectomy (LC).

BACKGROUND: Percutaneous transhepatic gallbladder drainage (PTGBD) is an important procedure for initial treatment of severe acute cholecystitis (AC) that is contraindicated for early laparoscopic cholecystectomy (LC). We presented our primary experience on a new approach of cholangiography via PTGBD (PTGBD-C) for preoperative delineation of biliary anatomy. METHODS: A retrospective analysis was conducted on 93 patients who received PTGBD followed by LC for AC, with allocation into 2 groups that were PTGBD with (PTGBD-C group, 32 patients) or without (PTGBD-N group, 61 patients) cholangiography. All the clinical data, including demographics, cholangiography findings, operations, and complications, were collected and analyzed. RESULTS: Cholangiography was attempted in 32 patients with a success of 31 cases, and the most common complication was transient fever in 3 patients. PTGBD-C group of patients showed significantly less operation time (83.2 ± 22.32 vs. 106.5 ± 40.25 min, P = 0.041) and conversion rate (0 vs. 2). There was no statistical difference in terms of postoperative hospitalization and complications. CONCLUSIONS: PTGBD-C is a feasible and safe procedure for severe AC patients with delayed LC. It has advantages of direct cholangiography, being easy to perform and cost-effective, thus should be considered for clinical usage.

KIAA1522 is a new biomarker of promoting the tumorigenesis and distant metastasis of colorectal carcinoma.

PURPOSE: Our research was absorbed into exploring the expression, clinicopathological value, biological significance and signaling pathway of KIAA1522 in colorectal carcinoma and its distant metastasis. MATERIALS AND METHODS: The expression of KIAA1522 and survival analysis in colorectal carcinoma (CRC) were assessed using GEPIA databases. Then we evaluated the expression of KIAA1522 immunohistochemically in tissue samples of 57 patients with colorectal carcinoma liver metastasis (CRLM). The correlations between the expression of KIAA1522, clinical significance and prognosis of these 57 patients with CRLM were analyzed. The migration and invasion of KIAA1522 were explored by western blotting, CCK-8, colony formation, flow cytometry, wound healing assays and transwell invasion in vitro and tail vein injection models in vivo. Then, transcriptome sequencing and gene set enrichment analysis was performed to identify the signaling pathways involved, while western blotting analysis and immunohistochemistry (IHC) were used to identify the expression of key genes in Notch signaling. RESULTS: KIAA1522 was overexpressed in CRLM tissues and colon cancer cell lines, and the expression of KIAA1522 in metastatic sites was positively correlated with that in primary sites. In addition, the overexpression of KIAA1522 is associated with poor clinicopathological features. Survival analysis showed that the overexpression of KIAA1522 predicted a low overall survival rate in patients with CRLM. Functional studies suggested that KIAA1522 promotes the proliferation, invasion and migration of colon carcinoma in vitro. KIAA1522 could promote distant metastasis of CRC in vivo. Moreover, KIAA1522 upregulated the Notch signaling pathway in colorectal cancer cell lines in vitro and lung metastatic nodes in vivo. CONCLUSION: In conclusion, it is suggested that the upregulation of KIAA1522 might promote the tumorigenicity and metastasis of colorectal carcinoma through Notch signaling pathway. KIAA1522 plays a carcinogenic role in the metastasis of colorectal carcinoma and might serve as a new molecular target for the treatment.

Effect of p18 on endothelial barrier function by mediating vascular endothelial Rab11a-VE-cadherin recycling.

Endothelial barrier integrity requires recycling of VE-cadherin to adherens junctions. Both p18 and Rab11a play significant roles in VE-cadherin recycling. However, the underlying mechanism and the role of p18 in activating Rab11a have yet to be elucidated. Performing in vitro and in vivo experiments, we showed that p18 protein bound to VE-cadherin before Rab11a through its VE-cadherin-binding domain (aa 1-39). Transendothelial resistance showed that overexpression of p18 promoted the circulation of VE-cadherin to adherens junctions and the recovery of the endothelial barrier. Silencing of p18 caused endothelial barrier dysfunction and prevented Rab11a-positive recycling endosome accumulation in the perinuclear recycling compartments. Furthermore, p18 knockdown in pulmonary microvessels markedly increased vascular leakage in mice challenged with lipopolysaccharide and cecal ligation puncture. This study showed that p18 regulated the pulmonary endothelial barrier function in vitro and in vivo by regulating the binding of Rab11a to VE-cadherin and the activation of Rab11a.

The postoperative choledochoscopy in the management of the residual hepatolithiasis involving the caudate lobe: A retrospective study.

ABSTRACT: To reveal the role of the postoperative choledochoscopy in treating the residual calculi in the caudate lobe (CL) of the liver.We recruited 66 patients with T-tube/percutaneous transhepatic cholangioscopy tract who still had residual gallstones in the CL at least 6 weeks after the operation. Imaging examinations determined the gallstones' locations in the patients, and all of them underwent the postoperative choledochoscopic examination through the T-tube/percutaneous transhepatic cholangioscopy tract for therapeutic intervention.Among the 66 patients, the residual gallstones were mostly located in the Spiegel lobe (48/66, 72.7%), and the residual gallstones that located in the origin of the CL bile branches were successfully determined in the 57 patients (57/66, 86.4%), the remaining 9 patients were unclear because the proximal ducts were severely narrow or even atresia. The mean frequency of the postoperative choledochoscopy was 3.6 (range, 1-10) times. There were 9 patients with complications, and no mortality occurred. In the origin-proved 57 patients, 6 patients failed to remove the gallstones altogether, and the final residual gallstone clearance rate was 77.3% (51/66). There was no significant difference between the Spiegel lobe and the other parts of the CL in determining the bile duct's origins, gallstone clearance rate, and complications. However, the frequency of choledochoscopy in the other parts of the CL was more than in the Spiegel lobe.The postoperative choledochoscopy, an essential method for treating the residual gallstones in the CL, commands high efficiency for calculi extraction and fewer complications. The main reasons for failing to remove the residual gallstones are that the bile duct's origins could not be determined, and the distal bile ducts are atretic in the CL.

Prognostic Value of Peripheral Whole Blood Cell Counts Derived Indexes in Gallbladder Carcinoma: A Systematic Review and Meta-Analysis.

BACKGROUND: Gallbladder carcinoma (GBC) is a rare gastrointestinal malignancy with poor prognosis. Adequate pre-treatment prediction of survival is essential for risk stratification and patient selection for aggressive surgery or adjuvant therapeutic strategy. Whole blood cell count (WBCC) derived indexes are broadly used as prognosticative biomarkers in various cancer types, but their utility in GBC needs to be validated. METHODS: An extensive literature review was conducted in line with PRISMA guideline until June 31 2020, to identify original studies concerning WBCC-derived indexes as prognostic indicators in GBC. All relative parameters were extracted and pooled for statistical analyses. RESULTS: Fourteen studies incorporating 2,324 patients were included with a high quality and low risk of biases. All 14 studies evaluated the prognostic value of NLR showing a significant correlation with OS in GBC patients (HR = 1.94, P <0.001). Elevated NLR was revealed to correlate with TNM stage (stages III and IV, OR = 4.65, P <0.001), tumor differentiation (OR = 2.37, P <0.042), CA 19-9 (SMD = 0.47, P = 0.01), but no significance was found with age, sex and CEA. Positive indicative value of MLR and PLR were also confirmed with a HR of 2.06 (P <0.001) and 1.34 (P <0.001), respectively. CONCLUSION: The WBCC-derived indexes including NLR, MLR/LMR and PLR were validated to be useful prognostic parameters for predicting survival outcomes in GBC patients. These series of indexes, especially NLR, could improve risk stratification and facilitate better patient selection for surgical resection or aggressive chemotherapy in the decision making of GBC patients.

RECK expression is associated with angiogenesis and immunogenic Tumor Microenvironment in Hepatocellular Carcinoma, and is a prognostic factor for better survival.

Angiogenesis and immunosuppression have been described as closely related processes that can occur in parallel. As an inhibitor of matrix metalloproteinase, whether the level of reversion-inducing cysteine-rich protein with Kazal motifs (RECK) in hepatocellular carcinoma (HCC) reflects a link between angiogenesis and immunosuppression is still unknown. We analyzed RNA expression, immune infiltration and survival of HCC from The Cancer Genome Atlas databases. Immune scores and stromal scores were calculated based on the ESTIMATE algorithm to quantify the immune and stromal components in HCC. The association between RECK and clinicopathological features was further investigated by immunohistochemistry on tissue microarray. We found that the prognosis of patients with high RECK expression was significantly better than that of patients with low RECK expression. High RECK expression was associated with high ESTIMATE Score, recruitment of more tumor-infiltrating lymphocytes, low tumor purity, and high PD-L1 expression. In addition, positive RECK expression was associated with a lower incidence of vascular invasion and recurrence, a lower level of alpha fetoprotein (AFP) and microvessel density and a better tumor differentiation. Multivariate analyses revealed that reduced RECK expression was an independent prognostic factor for recurrence and poor prognosis. In conclusion, high RECK expression reflects an immunogenic and hypovascularity status in HCC. RECK is a promising prognostic marker for survival of HCC and may act as a complementary indicator for patients to receive anti-angiogenic therapy or immunotherapy.

The Impact of Intraoperative Frozen Section on Resection Margin Status and Survival of Patients Underwent Pancreatoduodenectomy for Distal Cholangiocarcinoma.

BACKGROUND: Intraoperative frozen section (FS) is broadly used during pancreaticoduodenectomy (PD) to ensure a negative margin status, but its survival benefits on obtaining a secondary R0 resection for distal cholangiocarcinoma (dCCA) is controversial and unclear. METHODS: Clinical data of 107 patients who underwent PD for dCCA was retrospectively collected and divided into different groups based on use of FS (FS and non-FS groups) and status of resection margin (pR0, sR0 and R1 groups), and clinical parameters and survival of patients were compared and analyzed accordingly. RESULTS: There were 50 patients in FS group with a median survival of 28 months, 57 patients in non-FS group with a median survival of 27 months. There was no statistical difference between the two groups with Kaplan-Meier survival analysis (P = 0.347). There were 98 patients in R0 group (88 in pR0 and 10 in sR0) and nine patients in R1 group, with a median survival of 29 months and 22 months respectively, which showed a better survival in R0 group than in R1 group (P = 0.006). Survival analyses between subgroups revealed difference between pR0 and R1 group (P = 0.005), while no statistical difference concerning pR0 vs. sR0 (P = 0.211) and sR0 vs. R1 groups (P = 0.262). Multivariate Cox regression analysis revealed resection margin status, pre-operative biliary drainage and lymph node invasion to be independent prognostic factors for dCCA patients. CONCLUSIONS: Intraoperative FS should be recommended as it significantly increased the rate of R0 resection, which was positively related to a better survival. A primary R0 resection should also be encouraged and if not, a secondary R0 could be considered at the discretion of surgeons as it showed similar survival with primary R0 resection.

Clinical Benefit of Antiviral Agents for Hepatocellular Carcinoma Patients With Low Preoperative HBV-DNA Loads Undergoing Curative Resection: A Meta-Analysis.

BACKGROUND AND AIMS: The clinical benefit of adjuvant antiviral therapy after curative therapy for HCC in patients with high preoperative HBV-DNA loads has been studied widely but that in patients with low preoperative HBV-DNA loads remains controversial. The purpose of this study was to determine the effect of antiviral treatment prophylaxis on HBV reactivation, overall survival (OS), and postoperative liver function in patients with low preoperative HBV-DNA levels undergoing curative resection. METHODS: A meta-analysis was conducted by searching Web of Science, PubMed, Embase, and Cochrane Library until May 2020. We used REVMAN for data analysis and completed the study under the PRISMA guidelines. RESULTS: Three randomized trials and seven cohort studies, comprising of 1,131 individuals, were included in the meta-analysis. Antiviral treatment significantly reduced the rate of HBV reactivation after curative treatment of HCC, with a pooled risk ratio of 0.12 (95% c.i. 0.07 to 0.21; P < 0.00001). The trials were consistently favorable for the antiviral group, with a pooled hazard ratio of 0.52 (95% c.i. 0.37 to 0.74; P = 0.0002) in respect of OS rate. However, by pooling the data from studies that reported ALT on the 30th day postoperatively, the result didn't reach statistical significance (mean difference -4.38, 95% c.i. -13.83 to 5.07; P = 0.36). The I² values of the heterogeneity test for the above three comparisons are zero. CONCLUSION: Antiviral therapy during curative resection is effective in reducing HBV reactivation and improving OS rate in HCC patients with low viral load.

Role of the E3 Ubiquitin Ligase TRIM4 in Predicting the Prognosis of Hepatocellular Carcinoma.

The E3 ubiquitin ligase TRIM4 has been reported to regulate the assembly of the antiviral signalling complex, induce mitochondrial aggregation and sensitize cells to H2O2-induced death. However, the relationship between TRIM4 and human malignancies, including hepatocellular carcinoma (HCC), is unclear. In this study, we detected the expression of TRIM4 in 134 pairs of HCC tissues and peritumoural tissues and investigated the association of TRIM4 expression with the prognosis of HCC. We found that the TRIM4 expression was much lower in HCC tissues than in peritumoural tissues and was significantly associated with vascular invasion, tumour capsule and Hong Kong Liver Cancer (HKLC) stage. Univariate and multivariate analyses revealed that the TRIM4 expression was an independent prognostic factor for overall survival (OS) and recurrence-free survival (RFS) in our HCC cohort. Patients with higher TRIM4 expression had a lower incidence of intrahepatic recurrence and a higher OS rate (p<0.001 and p<0.01, respectively). These results were further validated in another independent cohort of 200 HCC patients. In conclusion, the TRIM4 level in HCC tissues is an independent prognostic factor for HCC patients. Close clinical monitoring is recommended for patients with low TRIM4 expression.

An Incidentally Discovered Hepatic Mass with Rim Calcification.

A wide array of pathologic abnormalities can cause hepatic calcifications, which are relatively uncommon and may result from both benign and malignant tumors, as well as inflammatory and infectious conditions. A pattern recognition approach is important to follow when faced with characterization of a calcified hepatic lesion. Radiologists should be aware of morphologic imaging features of calcified liver lesions to help differentiate benign from malignant lesions. Liver biopsy should be offered when the diagnosis is doubtful.

TMPRSS4 Drives Angiogenesis in Hepatocellular Carcinoma by Promoting HB-EGF Expression and Proteolytic Cleavage.

BACKGROUND AND AIMS: Heparin-binding epidermal growth factor (HB-EGF), a member of the epidermal growth factor family, plays a pivotal role in the progression of several malignancies, but its role and regulatory mechanisms in hepatocellular carcinoma (HCC) remain obscure. Here, we report that transmembrane protease serine 4 (TMPRSS4) significantly enhanced the expression and proteolytic cleavage of HB-EGF to promote angiogenesis and HCC progression. APPROACH AND RESULTS: A mechanistic analysis revealed that TMPRSS4 not only increased the transcriptional and translational levels of HB-EGF precursor, but also promoted its proteolytic cleavage by enhancing matrix metallopeptidase 9 expression through the EGF receptor/Akt/mammalian target of rapamycin/ hypoxia-inducible factor 1 α signaling pathway. In addition, HB-EGF promoted HCC proliferation and invasion by the EGF receptor/phosphoinositide 3-kinase/Akt signaling pathway. The level of HB-EGF in clinical samples of serum or HCC tissues from patients with HCC was positively correlated with the expression of TMPRSS4 and the microvessel density, and was identified as a prognostic factor for overall survival and recurrence-free survival, which suggests that HB-EGF can serve as a potential therapeutic target for HCC. More importantly, we provide a demonstration that treatment with the HB-EGF inhibitor cross-reacting material 197 alone or in combination with sorafenib can significantly suppress angiogenesis and HCC progression. CONCLUSIONS: HB-EGF can be regulated by TMPRSS4 to promote HCC proliferation, invasion, and angiogenesis, and the combination of the HB-EGF inhibitor cross-reacting material 197 with sorafenib might be used for individualized treatment of HCC.

Safety of Simultaneous Hepatectomy and Splenectomy in the Treatment of Hepatocellular Carcinoma Complicated with Hypersplenism: A Meta-analysis.

BACKGROUND: We conducted this meta-analysis to compare the efficacy and safety of simultaneous hepatectomy and splenectomy (HS) with hepatectomy alone (HA) in patients with hepatocellular carcinoma (HCC) and hypersplenism. MATERIALS AND METHODS: A systematic search was conducted in PubMed, Embase, Cochrane Library, and Wanfang Data through March 1, 2018, with no limits. Two investigators independently screened all retrieved studies. The investigators of the original publications were contacted if required information was absent. All the included studies were managed by EndNote X7. Quality assessment of the included studies was performed using a modified Newcastle-Ottawa Scale judgment. Extracted data for each endpoint were analyzed by using STATA 12.0 software. RESULTS: Thirteen studies, including a total of 1468 patients, comparing the effects of HS with HA were pooled in this meta-analysis. Outcomes including postoperative complications, perioperative mortality, intraoperative blood transfusion, and albumin (ALB) content at postoperation day (POD) 7 did not differ significantly between the two groups. Simultaneous approaches significantly promoted 1-, 3-, and 5-year disease-free survival (DFS) rates and overall survival (OS) rates, prolonged operation time, aggravated intraoperative blood loss, increased white blood cell (WBC) and platelet (PLT) counts at POD 7, and lowered total bilirubin (T-Bil) contents at POD 1 and 7. CONCLUSION: Compared to HA, HS is safer and more effective in ameliorating liver function and improving survival of HCC patients complicated with hypersplenism. This trial is registered with CRD42018093779.

Regional lymphadenectomy vs. extended lymphadenectomy for hilar cholangiocarcinoma (Relay-HC trial): study protocol for a prospective, multicenter, randomized controlled trial.

BACKGROUND: The prognostic benefits and safety of extended lymphadenectomy for hilar cholangiocarcinoma remain uncertain. The available evidence is still insufficient concerning its retrospective aspect. The aim of this study is to explore the clinical effect and safety of extended lymphadenectomy compared to regional lymphadenectomy in patients with hilar cholangiocarcinoma. METHODS: The Relay-HC trial is a prospective, multicenter, and randomized controlled trial. Seven hundred and thirty-four eligible patients with resectable perihilar cholangiocarcinoma across 15 tertiary hospitals in China will be randomly assigned (1:1) to receive either regional lymphadenectomy or extended lymphadenectomy. The primary objective is to determine the overall survival after the two approaches. Secondary objectives of the study include the evaluation of perioperative mortality, postoperative complication, and disease-free survival. This study has been approved by the ethics committee of each participating hospital. DISCUSSION: The Relay-HC trial is designed to investigate the prognostic benefits and safety of expanded lymphadenectomy for hilar cholangiocarcinoma. Currently, it has never been investigated in a prospective randomized controlled clinical trial. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR), ChiCTR1800015688 . Registered on 15 April 2018.

Determination of Water Content of Nitrogen Containing Hydrogen Sulfide by Karl Fischer Coulometric Titration.

Measuring the water content in natural gas is important for safety; however, complex matrixes make the results inaccurate. Natural gas contains hydrogen sulfide (H2S), which react with iodine (I2), causing Karl Fischer coulometric titration (KFCT) to give higher results. The KFCT method for the determination of water content of nitrogen containing H2S was investigated. A chilled mirror hygrometer offered a reference water content to calibrate the KFCT. The interfering of H2S was reduced by subtracting I2 consumed by H2S according to the reaction mechanism of ISO 10101; however, the modified results remained higher. A possible reaction mechanism with a stoichiometry of H2S to I2 of 1:2.5 was proposed. The improved KFCT method had an error of water content no more than (3 + 2%·x) mg/kg (x, water content in mg/kg) and had the potential of online monitoring of natural gas.