Yunxia Wan

NT-ProBNP Levels in Saliva and Its Clinical Relevance to Heart Failure

Background Current blood based diagnostic assays to detect heart failure (HF) have large intra-individual and inter-individual variations which have made it difficult to determine whether the changes in the analyte levels reflect an actual change in disease activity. Human saliva mirrors the body’s health and well being and ∼20% of proteins that are present in blood are also found in saliva. Saliva has numerous advantages over blood as a diagnostic fluid which allows for a non-invasive, simple, and safe sample collection. The aim of our study was to develop an immunoassay to detect NT-proBNP in saliva and to determine if there is a correlation with blood levels. Methods Saliva samples were collected from healthy volunteers (n = 40) who had no underlying heart conditions and HF patients (n = 45) at rest. Samples were stored at −80°C until analysis. A customised homogeneous sandwich AlphaLISA(R) immunoassay was used to quantify NT-proBNP levels in saliva. Results Our NT-proBNP immunoassay was validated against a commercial Roche assay on plasma samples collected from HF patients (n = 37) and the correlation was r2 = 0.78 (p<0.01, y = 1.705× +1910.8). The median salivary NT-proBNP levels in the healthy and HF participants were <16 pg/mL and 76.8 pg/mL, respectively. The salivary NT-proBNP immunoassay showed a clinical sensitivity of 82.2% and specificity of 100%, positive predictive value of 100% and negative predictive value of 83.3%, with an overall diagnostic accuracy of 90.6%. Conclusion We have firstly demonstrated that NT-proBNP can be detected in saliva and that the levels were higher in heart failure patients compared with healthy control subjects. Further studies will be needed to demonstrate the clinical relevance of salivary NT-proBNP in unselected, previously undiagnosed populations.

Circulating Fragments of N-Terminal Pro–B-Type Natriuretic Peptides in Plasma of Heart Failure Patients

BACKGROUND The use of nonstandardized N-terminal pro-B-type natriuretic peptide (NT-proBNP) assays can contribute to the misdiagnosis of heart failure (HF). Moreover, there is yet to be established a common consensus regarding the circulating forms of NT-proBNP being used in current assays. We aimed to characterize and quantify the various forms of NT-proBNP in the circulation of HF patients. METHODS Plasma samples were collected from HF patients (n = 20) at rest and stored at -80 °C. NT-proBNP was enriched from HF patient plasma by use of immunoprecipitation followed by mass spectrometric analysis. Customized homogeneous sandwich AlphaLISA® immunoassays were developed and validated to quantify 6 fragments of NT-proBNP. RESULTS Mass spectrometry identified the presence of several N- and C-terminally processed forms of circulating NT-proBNP, with physiological proteolysis between Pro2-Leu3, Leu3-Gly4, Pro6-Gly7, and Pro75-Arg76. Consistent with this result, AlphaLISA immunoassays demonstrated that antibodies targeting the extreme N or C termini measured a low apparent concentration of circulating NT-proBNP. The apparent circulating NT-proBNP concentration was increased with antibodies targeting nonglycosylated and nonterminal epitopes (P < 0.05). CONCLUSIONS In plasma collected from HF patients, immunoreactive NT-proBNP was present as multiple N- and C-terminally truncated fragments of the full length NT-proBNP molecule. Immunodetection of NT-proBNP was significantly improved with the use of antibodies that did not target these terminal regions. These findings support the development of a next generation NT-proBNP assay targeting nonterminal epitopes as well as avoiding the central glycosylated region of this molecule.

Quantification of D-dimer levels in human saliva

BACKGROUND Plasma D-dimer tests are currently used to exclude deep vein thrombosis and pulmonary embolism. Human saliva has numerous advantages over blood as a diagnostic sample. The aims of our study were to develop a reliable immunoassay to detect D-dimer levels in saliva, and to determine the correlation between salivary and blood D-dimer levels. RESULTS/METHODOLOGY: Saliva and blood samples were collected from 40 healthy volunteers. We developed a AlphaLISA® immunoassay with acceptable analytical performances to quantify D-dimer levels in the samples. The median salivary D-dimer levels were 138.1 ng/ml (morning) and 140.7 ng/ml (afternoon), and the plasma levels were 75.0 ng/ml. Salivary D-dimer levels did not correlate with plasma levels (p = 0.61). CONCLUSION For the first time, we have quantified D-dimer levels and found twofold increase in saliva (p < 0.05) than in plasma. Further studies are required to demonstrate the clinical relevance/utility of salivary D-dimer in patients with confirmed deep vein thrombosis and/or pulmonary embolism.

Within-Day Baseline Variation in Salivary Biomarkers in Healthy Men

Saliva is an easily accessible sample and offers practical and noninvasive biomarker solutions as an alternative to blood and urine-based diagnostics. Saliva contains a plethora of biomolecules such as nucleic acids, hormones, proteins, and electrolytes. On the other hand, little is known on the extent to which the biomolecules in saliva vary over time within a given person. This baseline information is crucial for future development of robust saliva-based diagnostics. We have collected unstimulated whole mouth saliva from 20 healthy young men at four times during the day, including before and after a meal. We measured the salivary cortisol, testosterone, C-reactive protein (CRP), stability of genomic DNA (gDNA) and DNA methylation levels of APC, P16INK4a, and PCQAP in these samples. We found that the salivary CRP, DNA methylation, and CD44 gDNA levels did not vary significantly across four time points (p > 0.05) while the salivary cortisol and testosterone levels significantly varied from the morning collection to the afternoon collection (p < 0.05). Furthermore, salivary cortisol levels were significantly affected by eating (p < 0.05). Our study offers a within-person baseline temporal assessment of several clinically relevant biomolecules and diagnostics, and suggests that salivary cortisol and testosterone levels vary over time in a given day whereas CRP and DNA methylation of tumor suppressor genes and CD44 amplification are stable throughout the day. Future research and clinical applications of salivary biomarkers and diagnostics should take into consideration their temporal variations.

A pilot study to demonstrate diagnostic potential of galectin-3 levels in saliva

Aim Heart failure (HF) affects millions of older individuals in both developed and low/middle-income countries. Serum galectin-3 levels have been shown to have prognostic value. However, its use as a diagnostic biomarker has not been explored. The aim was to establish a saliva galectin-3 reference range and to demonstrate the potential diagnostic utility of salivary and serum galectin-3 levels in assessing HF. Methods Blood and saliva samples were collected from age-matched healthy controls (n=51) and patients with HF (n=63). Customised immunoassays were developed to quantify salivary galectin-3 levels. The diagnostic performances of these assays were evaluated by receiver operator characteristic (ROC) curves analysis. Results The galectin-3 concentrations were significantly elevated in saliva and serum samples of patients with HF compared with controls (p<0.001 and p<0.0001, respectively). Using ROC curve analysis, both serum and salivary galectin-3 gave area under the curve (AUC)=0.86 and AUC=0.73, respectively. There was also a significant correlation (r=0.4, p<0.01) between serum and salivary galectin-3 levels. Conclusions For the first time, we have quantified galectin-3 levels in human saliva and have demonstrated potential clinical utility in diagnosing HF. Further, larger multicentre clinical trials are needed before salivary galectin-3 levels can be implemented in a clinical setting.

A multimarker approach to diagnose and stratify heart failure

BACKGROUND We have previously demonstrated that circulating NT-proBNP is truncated at the N and C termini. Aims of this study are three-fold: firstly to determine whether the NT-proBNP levels correlate with NYHA functional classes when measuring with different antibody pairs; secondly to evaluate the diagnostic potential of ProBNP and; thirdly to investigate whether combining NT-proBNP assays with or without ProBNP would lead to better diagnostic accuracies. METHODS Plasma samples were collected from healthy controls (n=52) and HF patients (n=46). Customized AlphaLISA® immunoassays were developed and validated to measure the concentrations of proBNP and NT-proBNP (with antibodies targeting 13-45, 13-76, 28-76). The diagnostic performance and predictive value of proBNP and NT-proBNP assays and their combinations were evaluated. RESULTS Plasma proBNP assay showed acceptable diagnostic performance. NT-proBNP13-76 assay is useful in diagnosing and stratifying HF patients. The diagnostic performance of NT-proBNP13-76 demonstrated improvement over commercial NT-proBNP tests. The combination of NT-proBNP13-76 with NT-proBNP28-76 assays gave the best diagnostic assay performance. CONCLUSION Our results demonstrate that while there is major heterogeneity in circulating NT-proBNP, specific epitopes of the peptides are extraordinarily stable, providing ideal targets for clinically useful diagnostic assays. Future new clinical diagnostic clinical trials should include a multimarker approach rather than using a single marker to diagnose HF.

Profiling of immunoglobulins in resting and mechanically stimulated saliva

BACKGROUND Dysregulation of salivary immunoglobulins has been implicated in illnesses ranging from periodontal disease to HIV aids and malignant cancers. Despite these advances there is a lack of agreement among studies with regard to the salivary immunoglobulin levels in healthy controls. METHODOLOGY Resting and mechanically stimulated saliva samples and matching serum samples were collected from healthy individuals (n = 33; 40-55 years of age; gender: 23 female, 10 male). A matrix-matched AlphaLISA(®) assay was developed to determine the concentrations of IgG1 and IgG4 in serum and saliva samples. CONCLUSION Clear relationships were observed in the flow rate and concentration of each immunoglobulin in the two types of saliva. This study affirms the need to establish and standardize collection methods before salivary IgGs are used for diagnostic purposes.

Salivary miRNA panel to detect HPV-positive and HPV-negative head and neck cancer patients

Head and neck squamous cell carcinomas (HNSCC) are a heterogeneous group of tumours that originate predominantly from the oral cavity, pharynx and larynx. Our aim was to determine whether salivary miRNA expression levels can diagnose these cancer subtypes. Saliva samples were collected from healthy controls (n=113, smoker and non-smokers), HPV-positive (n=54) and HPV-negative (n=47) HNSCC patients. The miRNA expression levels in saliva was quantified using qPCR. The potential of salivary miRNAs to discriminate these groups of patients was evaluated using multiple logistic regression with ROC analysis and a 10-fold cross-validation analysis. Salivary miRNA-9, -127, -134, -191, -222 and -455 were shown to discriminate a control group from a HPV-negative HNSCC patient group with a sensitivity of 60% and a specificity of 94%; whilst salivary miRNA-9,-134, -196b, -210, and -455 were the most parsimonious subset discriminating a control group from a HPV-positive HNSCC group, with a sensitivity of 65% and a specificity of 95%. Furthermore, miRNA-9, -134, -196b, -210 and -455 as a panel, was the most parsimonious subset to discriminate HPV-positive HNSCC patients from HPV-negative HNSCC patients. In addition, the expression levels of miRNA-9, -127, -196a, -196b, -210, -222 and -455 were significantly increased in the saliva collected from early stage HNSCC patients compared to controls. A future multi-centre confirmatory study is warranted to test the diagnostic performance of these salivary miRNA prior to clinical implementation.

Development of Paper-Based Analytical Devices for Minimizing the Viscosity Effect in Human Saliva

Rationale: Saliva as a sample matrix is rapidly gaining interest for disease diagnosis and point-of-care assays because it is easy to collect (non-invasive) and contains many health-related biomarkers. However, saliva poses particular problems relative to more common urine and blood matrices, which includes low analyte concentrations, lack of understanding of biomolecule transportation and inherent viscosity variability in human samples. While several studies have sought to improve assay sensitivity, few have addressed sample viscosity specifically. The goal of this study is to minimize the effect of sample viscosity on paper-based analytical devices (PADs) for the measurement of pH and nitrite in human saliva. Methods: PADs were used to measure salivary pH from 5.0 to 10.0 with a universal indicator consisting of chlorophenol red, phenol red and phenolphthalein. Nitrite determination was performed using the Griess reaction. Artificial saliva with viscosity values between 1.54 and 5.10 mPa∙s was tested on the proposed PAD. To ensure the proposed PADs can be tailored for use in-field analysis, the devices were shipped to Australia and tested with human specimens. Results: Initial experiments showed that viscosity had a significant impact on the calibration curve for nitrite; however, a more consistent curve could be generated when buffer was added after the sample, irrespective of sample viscosity. The linear range for nitrite detection was 0.1 to 2.4 mg/dL using the improved method. The nitrite measurement in artificial saliva also showed a good correlation with the standard spectrophotometry method (p=0.8484, paired sample t-test, n=20). Measured pH values from samples with varying viscosities correlated well with the results from our pH meter. Conclusions: The inherent variation of salivary viscosity that impacts nitrite and pH results can be addressed using a simple washing step on the PAD without the need for complex procedures.

A pilot study to profile salivary angiogenic factors to detect head and neck cancers

BackgroundEarly diagnosis of head and neck squamous cell carcinoma (HNSCCs) is an appealing way to increase survival rates in these patients as well as to improve quality of life post-surgery. Angiogenesis is a hallmark of tumor initiation and progression. We have investigated a panel of angiogenic factors in saliva samples collected from HNSCC patients and controls using the Bio-Plex ProTM assays.MethodsWe have identified a panel of five angiogenic proteins (sEGFR, HGF, sHER2, sIL-6Ra and PECAM-1) to be elevated in the saliva samples collected from HNSCC patients (n = 58) compared to a control cohort (n = 8 smokers and n = 30 non-smokers).ResultsHigh positive correlations were observed between the following sets of salivary proteins; sEGFR:sHER2, sEGFR:HGF, sEGFR:sIL-6Rα, sHER2:HGF and sHER2:sIL6Ra. A moderate positive correlation was seen between FGF-basic and sEGFR.ConclusionWe have shown that angiogenic factor levels in saliva can be used as a potential diagnostic biomarker panel in HNSCC.