Discovery and validation of urine markers of acute pediatric appendicitis using high-accuracy mass spectrometry

Observation Safely Reduces the Use of the Computerized Tomography in Medium-to-Low-Risk Patients with Suspected Acute Appendicitis: Results of a Randomized Controlled Trial

Objectives-The objective was to compare the effectiveness of observation in standard-of-care computed tomography (CT) in adult patients with suspected acute appendicitis (AA). Methods-Patients with clinically suspected AA and inconclusive diagnosis after primary clinical examination, laboratory examination, and transabdominal ultrasound (TUS) were eligible for the study, and they were randomized (1:1) to parallel groups: observation-group patients were observed for 8-12 h and then, repeated clinical and laboratory examinations and TUS were performed; CT group (control group) patients underwent abdominopelvic CT scan. The study utilized Statistical Analysis System 9.2 for data analysis, including tests, logistic regression, ROC analysis, and significance evaluation. Patients were enrolled in the study at Vilnius University Hospital Santaros Klinikos in Lithuania between December 2018 and June 2021. Results-A total of 160 patients (59 men, 101 women), with a mean age of 33.7 ± 14.71, were included, with 80 patients in each group. Observation resulted in a reduced likelihood of a CT scan compared with the CT group (36.3% vs. 100% p < 0.05). One diagnostic laparoscopy was performed in the observation group; there were no cases of negative appendectomy (NA) in the CT group. Both conditional CT and observation pathways resulted in high sensitivity and specificity (97.7% and 94.6% vs. 96.7% and 95.8%). Conclusions-Observation including the repeated evaluation of laboratory results and TUS significantly reduces the number of CT scans without increasing NA numbers or the number of complicated cases.

Leucine-Rich Alpha-2-Glycoprotein as a non-invasive biomarker for pediatric acute appendicitis: a systematic review and meta-analysis

The aim of this study was to analyze the diagnostic performance of Leucine-Rich Alpha-2-Glycoprotein (LRG1) in pediatric acute appendicitis (PAA). We conducted a systematic review of the literature in the main databases of medical bibliography. Two independent reviewers selected the articles and extracted relevant data. Methodological quality was assessed using the QUADAS2 index. A synthesis of the results, standardization of the metrics and 4 random-effect meta-analyses were performed. Eight studies with data from 712 participants (305 patients with confirmed diagnosis of PAA and 407 controls) were included in this review. The random-effect meta-analysis of serum LRG1 (PAA vs control) resulted in a significant mean difference (95% CI) of 46.76 μg/mL (29.26-64.26). The random-effect meta-analysis for unadjusted urinary LRG1 (PAA vs control) resulted in a significant mean difference (95% CI) of 0.61 μg/mL (0.30-0.93). The random-effect meta-analysis (PAA vs control) for urinary LRG1 adjusted for urinary creatinine resulted in a significant mean difference (95% CI) of 0.89 g/mol (0.11-1.66).   Conlusion: Urinary LRG1 emerges as a potential non-invasive biomarker for the diagnosis of PAA. On the other hand, due to the high between-study heterogeneity, the results on serum LRG1 should be interpreted with caution. The only study that analyzed salivary LRG1 showed promising results. Further prospective studies are needed to confirm these findings. What is Known: • Pediatric acute appendicitis continues to be a pathology with a high rate of diagnostic error. • Invasive tests, although useful, are a source of stress for patients and their parents. What is New: • LRG1 emerges as a promising urinary and salivary biomarker for the noninvasive diagnosis of pediatric acute appendicitis.

LRG1 is an adipokine that promotes insulin sensitivity and suppresses inflammation

While dysregulation of adipocyte endocrine function plays a central role in obesity and its complications, the vast majority of adipokines remain uncharacterized. We employed bio-orthogonal non-canonical amino acid tagging (BONCAT) and mass spectrometry to comprehensively characterize the secretome of murine visceral and subcutaneous white and interscapular brown adip ocytes. Over 600 proteins were identified, the majority of which showed cell type-specific enrichment. We here describe a metabolic role for leucine-rich α-2 glycoprotein 1 (LRG1) as an obesity-regulated adipokine secreted by mature adipocytes. LRG1 overexpression significantly improved glucose homeostasis in diet-induced and genetically obese mice. This was associated with markedly reduced white adipose tissue macrophage accumulation and systemic inflammation. Mechanistically, we found LRG1 binds cytochrome c in circulation to dampen its pro-inflammatory effect. These data support a new role for LRG1 as an insulin sensitizer with therapeutic potential given its immunomodulatory function at the nexus of obesity, inflammation, and associated pathology.

Diagnostic performance of calprotectin and APPY-1 test in pediatric acute appendicitis: a systematic review and a meta-analysis

BACKGROUND

Pediatric acute appendicitis (AA) is a challenging pathology to diagnose. In the last decades, multiple biomarkers have been evaluated in different human biological samples to improve diagnostic performance. This study aimed to examine the diagnostic performance of serum, fecal and urinary calprotectin as well as the role of the APPY-1 biomarker panel in pediatric acute appendicitis.

METHODS

We conducted a systematic review of the literature that involved an extensive search in the main databases of medical bibliography (Medline, PubMed, Web of Science and SciELO). Two independent reviewers selected the relevant articles based on the previously defined inclusion and exclusion criteria. Methodological quality of the selected article was rated using the QUADAS2 index. Data extraction was performed by two independent reviewers. A synthesis of the results, a standardization of the metrics and two random-effect meta-analyses, one for serum calprotectin and one for APPY-1, were performed.

RESULTS

The research resulted in 173 articles. Thirty-eight duplicates were removed. Among the remaining 135 articles, we excluded 125 following the inclusion and exclusion criteria, resulting in the 10 studies included in this review. This systematic review included data from of 3901 participants (1276 patients with confirmed diagnosis of AA and 2625 controls). The age of the participants ranged from 0 to 21 years. Four of the studies compared serum calprotectin values and reported significant differences between groups, but inconsistent results regarding cutoff points, sensitivity and specificity. Two publications compared urinary values of calprotectin and presented inconsistent results regarding sensitivity and specificity as well. One publication evaluated the diagnostic performance of fecal calprotectin, but it did not provide data on measured values. Four studies evaluated the diagnostic performance of APPY-1 test in pediatric acute appendicitis. The calculated pooled sensitivity and specificity of those studies were 97.37 (95% CI 95.60-98.44) and 36.74 (95% CI 32.28-41.44), respectively, and the calculated pooled NLR, 0.0714 (95% CI 0.041-0.115).

CONCLUSION

Serum calprotectin has limited diagnostic yield in pediatric acute appendicitis. Its performance seems to increase with the hours of clinical evolution and in advanced AA, although the evidence is limited. There is not enough evidence on the usefulness of urinary or fecal calprotectin in the diagnosis of pediatric acute appendicitis. On the other hand, the APPY-1 is a reliable test to exclude the diagnosis of AA in patients at low or moderate risk according to PAS and Alvarado Score.

LRG1: an emerging player in disease pathogenesis

The secreted glycoprotein leucine-rich α-2 glycoprotein 1 (LRG1) was first described as a key player in pathogenic ocular neovascularization almost a decade ago. Since then, an increasing number of publications have reported the involvement of LRG1 in multiple human conditions including cancer, diabetes, cardiovascular disease, neurological disease, and inflammatory disorders. The purpose of this review is to provide, for the first time, a comprehensive overview of the LRG1 literature considering its role in health and disease. Although LRG1 is constitutively expressed by hepatocytes and neutrophils, Lrg1-/- mice show no overt phenotypic abnormality suggesting that LRG1 is essentially redundant in development and homeostasis. However, emerging data are challenging this view by suggesting a novel role for LRG1 in innate immunity and preservation of tissue integrity. While our understanding of beneficial LRG1 functions in physiology remains limited, a consistent body of evidence shows that, in response to various inflammatory stimuli, LRG1 expression is induced and directly contributes to disease pathogenesis. Its potential role as a biomarker for the diagnosis, prognosis and monitoring of multiple conditions is widely discussed while dissecting the mechanisms underlying LRG1 pathogenic functions. Emphasis is given to the role that LRG1 plays as a vasculopathic factor where it disrupts the cellular interactions normally required for the formation and maintenance of mature vessels, thereby indirectly contributing to the establishment of a highly hypoxic and immunosuppressive microenvironment. In addition, LRG1 has also been reported to affect other cell types (including epithelial, immune, mesenchymal and cancer cells) mostly by modulating the TGFβ signalling pathway in a context-dependent manner. Crucially, animal studies have shown that LRG1 inhibition, through gene deletion or a function-blocking antibody, is sufficient to attenuate disease progression. In view of this, and taking into consideration its role as an upstream modifier of TGFβ signalling, LRG1 is suggested as a potentially important therapeutic target. While further investigations are needed to fill gaps in our current understanding of LRG1 function, the studies reviewed here confirm LRG1 as a pleiotropic and pathogenic signalling molecule providing a strong rationale for its use in the clinic as a biomarker and therapeutic target.

Novel molecular biomarkers and diagnosis of acute appendicitis in children

Reliable and efficient diagnosis of pediatric appendicitis is essential for the establishment of a clinical management plan and improvement of patient outcomes. Current strategies used to diagnose a child presenting with a suspected appendicitis include laboratory studies, clinical scores and diagnostic imaging. Although these modalities work in conjunction with each other, one optimal diagnostic strategy has yet to be agreed upon. The recent introduction of precision medicine techniques such as genomics, transcriptomics, proteomics and metabolomics has increased both the diagnostic sensitivity and specificity of appendicitis. Using these novel strategies, the integration of precision medicine into clinical practice via point-of-care technologies is a plausible future. These technologies would assist in the screening, diagnosis and prognosis of pediatric appendicitis.

Serum and Urine Biomarker Leucine-Rich Alpha-2 Glycoprotein 1 Differentiates Pediatric Acute Complicated and Uncomplicated Appendicitis

PURPOSE

This prospective, single-center cohort study analyzes the potential of inflammatory protein mediator leucine-rich alpha-2 glycoprotein 1 (LRG1) for the early and accurate diagnosis of acute appendicitis (AA), and differentiation of acute complicated (AcA) from uncomplicated appendicitis (AuA).

METHODS

Participants were divided into the AcA, AuA, and control groups, and their serum (s-LRG1) and urine LRG1 (u-LRG1) levels were assayed preoperatively on the second and fifth postoperative days.

RESULTS

153 patients participated, 97 had AA. Preoperative u-LRG1 with a cut-off value of 0.18 μg/mL generated an area under the receiver operated characteristic (AUC) curve of 0.70 (95% CI 0.62-0.79) for AA versus control (p < 0.001), while the results for AcA versus AuA were not significant (AUC 0.60, 95% CI 0.49-0.71, p = 0.089). The s-LRG1 levels of AA versus the control with a cut-off value of 51.69 μg/mL generated an AUC of 0.94 (95% CI 0.91-0.99, p < 0.001). The cut-off value of s-LRG1 was 84.06 μg/mL for diagnosis of AcA from AuA, and therefore, significant (AUC 0.69, 95% CI 0.59-0.80, p = 0.001).

CONCLUSIONS

LRG1 exhibited excellent diagnostic performance as an inexpensive, non-invasive, rapid, and accurate biomarker able to reflect the pathogenesis of AA. LRG1 has the potential to replace advanced imaging to diagnose clinically ambiguous AA cases.

Comparison of leucine-rich alpha-2-glycoprotein-1 (LRG-1) plasma levels between patients with and without appendicitis, a case-controlled study

Acute appendicitis (AA) is the first cause of emergency surgery. Leucine-Rich Alpha-2-Glycoprotein 1 (LRG1) has been shown to be a potential biomarker in cases of AA in children, but there are conflicting results for its use in adults. The objective of this study is to compare the median plasma values of LRG1 in patients with acute abdomen with and without appendicitis. This case–control study was conducted prospectively at the emergency room (ER) of a tertiary teaching hospital, between March 1st, 2011 and December 31st, 2012. Patients with recent abdominal pain, aged 18–70 years who attended at the ER were included in the study. Blood samples were drawn at the first presentation. Those who were submitted to surgery and had a pathology report of AA were considered as cases. Those without a need for surgery and treated for other conditions, e.g., pelvic inflammatory disease, were considered as controls. Follow-up in controls was made up to 30 days. LRG1 plasma median values were measured using an ELISA kit and compared between groups. A total of 28 participants, 14 cases with acute appendicitis and 14 controls, were included. The median (range) values of leucine-rich alpha-2-glycoprotein-1 level in the group with appendicitis and control group were 8.8 ng/ml (5.5–31) and 11 (4.6–108) ng/ml, respectively (Mann–Whitney test P = 0.26). Median plasma leucine-rich alpha-2-glycoprotein-1 levels were not useful in diagnosing Acute Appendicitis in patients with acute abdominal pain.

Salivary biomarker for acute appendicitis in children: a pilot study

PURPOSE

Assays of salivary biomarkers for diagnosis are gaining popularity in pediatric diseases due to their non-invasive nature. Our pilot project aims to evaluate the utility of salivary leucine-rich-alpha-2-glycoprotein (LRG) in the diagnosis of pediatric acute appendicitis (AA).

METHODS

We prospectively recruited 34 patients, aged between 4 and 16 years, admitted with acute abdominal pain suspicious of appendicitis. The patients' demography, clinical characteristics, laboratory investigations, imaging examination results, operative findings, and discharge diagnoses were recorded. We compared the diagnostic performance of the patients' total white counts, neutrophil percentages, C-reactive protein, and saliva LRG levels. Saliva samples were obtained using the SalivaBio Children's Swab and LRG levels were quantified using a commercially available LRG enzyme-linked immunosorbent assay (ELISA) kit. IRB approval was obtained.

RESULTS

Seventeen patients had a confirmed diagnosis of appendicitis on histology. Another 17 were confirmed not to have appendicitis after a minimum of 24 h of hospitalization, with further verification via telephone interview 2 weeks later. The median levels of saliva LRG were elevated in patients with AA as compared to those without (P = 0.008). At a cutoff of LRG 0.33 ng/μg, we obtained a diagnostic specificity of 100% and sensitivity of 35.3%.

CONCLUSION

Our proof-of-concept study demonstrated the diagnostic potential of saliva LRG for appendicitis in children. The distinct advantage of saliva LRG assays is that the procedure is simple, pain-free, and requires no specialized skill. Further study with a larger cohort is needed to verify our results.

Determining acute complicated and uncomplicated appendicitis using serum and urine biomarkers: interleukin-6 and neutrophil gelatinase-associated lipocalin

PURPOSE

The study aim is to determine whether serum and urine interleukin-6 (IL-6) and neutrophil gelatinase-associated lipocalin (NGAL) can be included in the early diagnostic algorithm for pediatric appendicitis.

METHODS

Prospective single-center cohort study included 92 children divided into control, acute complicated appendicitis (AcA) and acute uncomplicated appendicitis (AnA) groups. Serum and urine samples were assayed for IL-6 and NGAL preoperatively, and on the second and fifth postoperative days. Intraoperative and bacteriological findings divided the appendicitis patients.

RESULTS

Average serum biomarker levels were higher in appendicitis patients versus the control, and the following values were produced via receiver operating characteristic (ROC) analysis. NGAL and IL-6 cutoff values were 113.95 ng/ml and 24.64 pg/ml, respectively, NGAL had 68.3% sensitivity and 65.5% specificity, while IL-6 had 72.6% and 86.2%. Comparing AcA and AnA, IL-6 was the only biomarker of significance yielding 77.4% sensitivity and 58.1% specificity with a 26.43 pg/ml cutoff value. Urine biomarkers were non-specific in differentiation appendicitis severity and ultimately, between infectious and non-infectious disease.

CONCLUSION

Although NGAL provided measurable useful diagnostic information in evaluating children for appendicitis, its values were not sufficient for appendicitis severity. Serum IL-6 remains a strong biomarker for suspected acute appendicitis and has promising results predicting its severity.

Prohibitin is a prognostic marker and therapeutic target to block chemotherapy resistance in Wilms' tumor

Wilms' tumor is the most common type of childhood kidney cancer. To improve risk stratification and identify novel therapeutic targets for patients with Wilms' tumor, we used high-resolution mass spectrometry proteomics to identify urine tumor markers associated with Wilms' tumor relapse. We determined the urine proteomes at diagnosis of 49 patients with Wilms' tumor, non-Wilms' tumor renal tumors, and age-matched controls, leading to the quantitation of 6520 urine proteins. Supervised analysis revealed specific urine markers of renal rhabdoid tumors, kidney clear cell sarcomas, renal cell carcinomas as well as those detected in patients with cured and relapsed Wilms' tumor. In particular, urine prohibitin was significantly elevated at diagnosis in patients with relapsed as compared with cured Wilms' tumor. In a validation cohort of 139 patients, a specific urine prohibitin ELISA demonstrated that prohibitin concentrations greater than 998 ng/mL at diagnosis were significantly associated with ultimate Wilms' tumor relapse. Immunohistochemical analysis revealed that prohibitin was highly expressed in primary Wilms' tumor specimens and associated with disease stage. Using functional genetic experiments, we found that prohibitin was required for the growth and survival of Wilms' tumor cells. Overexpression of prohibitin was sufficient to block intrinsic mitochondrial apoptosis and to cause resistance to diverse chemotherapy drugs, at least in part by dysregulating factors that control apoptotic cytochrome c release from mitochondrial cristae. Thus, urine prohibitin may improve therapy stratification, noninvasive monitoring of treatment response, and early disease detection. In addition, therapeutic targeting of chemotherapy resistance induced by prohibitin dysregulation may offer improved therapies for patients with Wilms' and other relapsed or refractory tumors.

Gestational Diabetes Mellitus Regulatory Network Identifies hsa-miR-145-5p and hsa-miR-875-5p as Potential Biomarkers

BACKGROUND

Gestational diabetes mellitus (GDM) is pregnancy-related diabetes with vital risks for both mother and the fetus. Molecular studies represent one of the popular approaches for investigating mechanisms associated with the disease nature. One of which is through interaction network analysis via Cytoscape V. 3.6.1.

METHODS

In this study, the microRNA (miRNA) expression array of GSE98043 from gene expression omnibus (GEO) database was retrieved and screened. We identified 12 differentially expressed (DE) miRNAs (P ≤ 0.05) and nine target hub-bottleneck genes (disease score > 1) for GDM based on miRNA-target interactions created via plugin ClueGO + Cluepedia + STRING.

RESULTS

MiRNA-target information showed that the miRNAs are mostly up-regulated and hsa-miR-145-5p and hsa-miR-875-5p targets the most genes. Among target genes, IL6, GCG, APOB, and ALB have the highest associations with DE-miRNAs. Gene ontology analysis based on biological processes identification via ClueGO + CluePedia, in addition, showed that target hub-bottlenecks are mainly related to metabolism functions and any changes in this regulatory network could impose fundamental alterations in these processes.

CONCLUSIONS

It can be concluded that via these introduced miRNAs and their targets, the molecular tests for diagnosis and treatment of GDM can be improved after applying validation approaches.

Diagnosis of acute pediatric appendicitis from children with inflammatory diseases by combination of metabolic markers and inflammatory response variables

BACKGROUND

The discovery of new metabolic markers may be helpful for early diagnosis of acute pediatric appendicitis (APA). However, no studies have been reported regarding identification of potential metabolic markers for the APA diagnosis by metabonomics.

METHODS

Serum samples of APA (n=32), non-appendicitis inflammation (NAI, n=32) and healthy children (HS, n=65) were analyzed by the 1H NMR-based metabonomics. A logistic regression model was established to screen the most efficient markers combinations for classification. Forty double-blind samples were further validated the model.

RESULTS

Nine blood metabolites that were different in the APA group from other groups were identified. To differentiate APA from HS, single variable of acetate, formate, white blood cell (WBC) and C-reactive protein (CRP) showed a high diagnostic value (area under the receiver operating characteristic [AUROC]<0.92), while they had a weak diagnostic value (AUROC<0.77) for identifying the APA and NAI. By contrast, the AUROC values of leucine (0.799) were higher than that of WBC and CRP. A combination of five variables, i.e. leucine, lactate, betaine, WBC and CRP, showed a high diagnostic value (AUROC=0.973) for the APA discriminating from the NAI, and the sensitivity and specificity were 93.8% and 93.7%, respectively. Further double-blind sample prediction showed that the accuracy of the model was 85% for 40 unknown samples.

CONCLUSIONS

The current study provides useful information in our understanding of the metabolic alterations associated with APA and indicates that measurement of these metabolites in serum effectively aids in the clinical identification of APA.

A novel noninvasive appendicitis score with a urine biomarker

PURPOSE

The aim of our study was to develop an appendicitis score incorporating a urine biomarker, Leucine rich alpha-2-glycoprotein (LRG), for evaluation of children with abdominal pain.

METHODS

From January to August 2017 we prospectively enrolled children aged 4-16 years old admitted for suspected appendicitis. Urine samples for LRG analysis were obtained preoperatively and quantified by enzyme-linked immunosorbent assay (ELISA) after correction for patient hydration status. The diagnosis of appendicitis was based on operative findings and histology. Logistic regression was used to identify prospective predictors.

RESULTS

A total of 148 patients were recruited, of which 42(28.4%) were confirmed appendicitis. Our Appendicitis Urinary Biomarker (AuB) model incorporated urine LRG with 3 clinical predictors: 'constant pain', 'right iliac fossa tenderness', 'pain on percussion'. Area under the ROC curve for AuB was 0.82 versus 0.78 for the Pediatric Appendicitis Score (PAS) on the same cohort of patients. A model-calculated risk score of <0.15 is interpreted as low risk of appendicitis. Sensitivity for the AuB at this cutoff was 97.6%, specificity 37.7%, negative predictive value 97.6%, positive predictive value 38.3%, and negative likelihood ratio 0.06.

CONCLUSION

The noninvasive AuB score appears promising as a diagnostic tool for excluding appendicitis in children without the need for blood sampling.

TYPE OF STUDY

Study of diagnostic test.

LEVEL OF EVIDENCE

Level III.

Metabolic analysis of acute appendicitis by using system biology approach

AIM

Introducing possible suitable compound as diagnostic agent in appendicitis is aim of this investigation.

BACKGROUND

Appendicitis diagnosis is a difficult step in treatment of disease due to complex abdominal pain signal which may be refer to the non-appendicitis pain.

METHODS

Gene expression profiles of children with non-preforated appendicitis in comparison with the samples with non- appendicitis abdominal pain are analysis via protein - protein interaction (PPI) and the critical compounds are introduced by STITCH.

RESULTS

Ten compounds including including MgATP, glycerol, MgADP, calcium ions, chloride, magnesium, phosphate, sulphate, acetate, and sodium are introduced as possible biomarker panel to differentiate appendicitis from the other abdominal pains.

CONCLUSION

A laboratory method such as flame photometry based on metal detection for diagnosis of appendicitis is possible, however more investigations are required.

Current state of the art for enhancing urine biomarker discovery

INTRODUCTION

Urine is a highly desirable biospecimen for biomarker analysis because it can be collected recurrently by non-invasive techniques, in relatively large volumes. Urine contains cellular elements, biochemicals, and proteins derived from glomerular filtration of plasma, renal tubule excretion, and urogenital tract secretions that reflect, at a given time point, an individual's metabolic and pathophysiologic state.

AREAS COVERED

High-resolution mass spectrometry, coupled with state of the art fractionation systems are revealing the plethora of diagnostic/prognostic proteomic information existing within urinary exosomes, glycoproteins, and proteins. Affinity capture pre-processing techniques such as combinatorial peptide ligand libraries and biomarker harvesting hydrogel nanoparticles are enabling measurement/identification of previously undetectable urinary proteins. Expert commentary: Future challenges in the urinary proteomics field include a) defining either single or multiple, universally applicable data normalization methods for comparing results within and between individual patients/data sets, and b) defining expected urinary protein levels in healthy individuals.

A comprehensive analysis and annotation of human normal urinary proteome

Biomarkers are measurable changes associated with the disease. Urine can reflect the changes of the body while blood is under control of the homeostatic mechanisms; thus, urine is considered an important source for early and sensitive disease biomarker discovery. A comprehensive profile of the urinary proteome will provide a basic understanding of urinary proteins. In this paper, we present an in-depth analysis of the urinary proteome based on different separation strategies, including direct one dimensional liquid chromatography–tandem mass spectrometry (LC/MS/MS), two dimensional LC/MS/MS, and gel-eluted liquid fraction entrapment electrophoresis/liquid-phase isoelectric focusing followed by two dimensional LC/MS/MS. A total of 6085 proteins were identified in healthy urine, of which 2001 were not reported in previous studies and the concentrations of 2571 proteins were estimated (spanning a magnitude of 10⁶) with an intensity-based absolute quantification algorithm. The urinary proteins were annotated by their tissue distribution. Detailed information can be accessed at the “Human Urine Proteome Database” (www.urimarker.com/urine).

How to diagnose an acutely inflamed appendix; a systematic review of the latest evidence

Acute appendicitis is the most common condition that presents with an acute abdomen needing emergency surgery. Despite this common presentation, correctly diagnosing appendicitis remains a challenge as clinical signs or positive blood results can be absent in 55% of the patients. The reported proportion of missed diagnoses of appendicitis ranges between 20% and 40%. A delay or mis-diagnosis of appendicitis can result in severe complications such as perforation, abscess formation, sepsis, and intra-abdominal adhesions. Literature has shown that patients who had a negative appendectomy suffer post-op complications and infections secondary to hospital stays; there have even been reported cases of fatality. It is therefore crucial that timely and accurate diagnosis of appendicitis is achieved to avoid complications of both non-operating as well as unnecessary surgical intervention. The aim of this review is to systematically report and analyse the latest evidence on the different approaches used in diagnosing appendicitis. We include discussions of clinical scoring systems, laboratory tests, latest innovative bio-markers and radiological imaging.

Circulating human leucine-rich α-2-glycoprotein 1 mRNA and protein levels to detect acute appendicitis in patients with acute abdominal pain

BACKGROUND

Elevated levels of circulating plasma and urine leucine-rich-2-glycoprotein-1 (LRG1) protein has been found in patients with acute appendicitis (AA) and may be useful for diagnosis. This study aimed to investigate whether combined tests including circulating LRG1 mRNA levels improve the early diagnosis of AA.

METHODS

Between December 2011 and October 2012, a prospective study was conducted on patients aged 18years or older presenting to the ED with acute abdominal pain (<7days of symptom onset). Levels of whole blood LRG1 mRNA and plasma LRG1 protein taken from these patients within 24h of arrival (mean 12.4h) were analyzed. The primary outcome was AA.

RESULTS

Eighty-four patients (40 (47.6%) with AA and 44 (52.4%) without AA; mean age 35years; 41.6% males) were recruited. Median whole blood LRG1 mRNA and plasma LRG1 levels were higher in AA patients than in non-AA. Of 40 AA patients, 13 (32.5%) were diagnosed as complicated AA. In ROC analysis of LRG1 mRNA (normalized to GAPDH), LRG1 protein and Alvarado score for discriminating AA and non-AA, the areas under the curve (AUC) were 0.723, 0.742 and 0.805 respectively. The AUC of combination of normalized LRG1 mRNA, LRG1 protein and Alvarado score was 0.845.

CONCLUSION

A combination of modified whole blood LRG1 mRNA levels, plasma LRG1 protein and Alvarado score at the ED may be useful to diagnose simple and complicated AA from other causes of abdominal pain.

Towards comprehensive and quantitative proteomics for diagnosis and therapy of human disease

Given superior analytical features, MS proteomics is well suited for the basic investigation and clinical diagnosis of human disease. Modern MS enables detailed functional characterization of the pathogenic biochemical processes, as achieved by accurate and comprehensive quantification of proteins and their regulatory chemical modifications. Here, we describe how high-accuracy MS in combination with high-resolution chromatographic separations can be leveraged to meet these analytical requirements in a mechanism-focused manner. We review the quantification methods capable of producing accurate measurements of protein abundance and posttranslational modification stoichiometries. We then discuss how experimental design and chromatographic resolution can be leveraged to achieve comprehensive functional characterization of biochemical processes in complex biological proteomes. Finally, we describe current approaches for quantitative analysis of a common functional protein modification: reversible phosphorylation. In all, current instrumentation and methods of high-resolution chromatography and MS proteomics are poised for immediate translation into improved diagnostic strategies for pediatric and adult diseases.

Urinary biomarkers in pediatric appendicitis

PURPOSE

The diagnosis of pediatric appendicitis is still a challenge, resulting in perforation and negative appendectomies. The aim of this study was to evaluate novel biomarkers in urine and to use the most promising biomarkers in conjunction with the Pediatric Appendicitis Score (PAS), to see whether this could improve the accuracy of diagnosing appendicitis.

METHODS

A prospective study of children with suspected appendicitis was conducted with assessment of PAS, routine blood tests, and measurements of four novel urinary biomarkers: leucine-rich α-2-glycoprotein (LRG), calprotectin, interleukin 6 (IL-6), and substance P. The biomarkers were blindly determined with commercial ELISAs. Urine creatinine was used to adjust for dehydration. The diagnosis of appendicitis was based on histopathological analysis.

RESULTS

Forty-four children with suspected appendicitis were included, of which twenty-two (50 %) had confirmed appendicitis. LRG in urine was elevated in children with appendicitis compared to children without (p < 0.001), and was higher in children with gangrenous and perforated appendicitis compared to those with phlegmonous appendicitis (p = 0.003). No statistical significances between groups were found for calprotectin, IL-6 or substance P. LRG had a receiver operating characteristic area under the curve of 0.86 (95 % CI 0.79-0.99), and a better diagnostic performance than all routine blood tests. LRG in conjunction with PAS showed 95 % sensitivity, 90 % specificity, 91 % positive predictive value, and 95 % negative predictive value.

CONCLUSION

LRG, adjusted for dehydration, is a promising novel urinary biomarker for appendicitis in children. LRG in combination with PAS has a high diagnostic performance.

Investigation of urine proteome of preterm newborns with respiratory pathologies

A serious problem during intensive care and nursing of premature infants is the invasiveness of many examination methods. Urine is an excellent source of potential biomarkers due to the safety of the collection procedure. The purpose of this study was to determine the features specific for the urine proteome of preterm newborns and their changes under respiratory pathologies of infectious and non-infectious origin. The urine proteome of 37 preterm neonates with respiratory diseases and 10 full-term newborns as a control group were investigated using the LC-MS/MS method. The total number of identified proteins and unique peptides was 813 and 3672 respectively. In order to further specify the defined infant-specific dataset these proteins were compared with urine proteome of healthy adults (11 men and 11 pregnant women) resulting in 94 proteins found only in infants. Pairwise analysis performed for label-free proteomic data revealed 36 proteins which reliably distinguished newborns with respiratory disorders of infectious genesis from those with non-infectious pathologies, including: proteins involved in cell adhesion (CDH-2,-5,-11, NCAM1, TRY1, DSG2), metabolism (LAMP1, AGRN, TPP1, GPX3, APOD, CUBN, IDH1), regulation of enzymatic activity (SERPINA4, VASN, GAPDH), inflammatory and stress response (CD55, CD 93, NGAL, HP, TNFR, LCN2, AGT, S100P, SERPINA1/C1/B1/F1).

Advancing Urinary Protein Biomarker Discovery by Data-Independent Acquisition on a Quadrupole-Orbitrap Mass Spectrometer

The promises of data-independent acquisition (DIA) strategies are a comprehensive and reproducible digital qualitative and quantitative record of the proteins present in a sample. We developed a fast and robust DIA method for comprehensive mapping of the urinary proteome that enables large scale urine proteomics studies. Compared to a data-dependent acquisition (DDA) experiments, our DIA assay doubled the number of identified peptides and proteins per sample at half the coefficients of variation observed for DDA data (DIA = ∼8%; DDA = ∼16%). We also tested different spectral libraries and their effects on overall protein and peptide identifications and their reproducibilities, which provided clear evidence that sample type-specific spectral libraries are preferred for reliable data analysis. To show applicability for biomarker discovery experiments, we analyzed a sample set of 87 urine samples from children seen in the emergency department with abdominal pain. The whole set was analyzed with high proteome coverage (∼1300 proteins/sample) in less than 4 days. The data set revealed excellent biomarker candidates for ovarian cyst and urinary tract infection. The improved throughput and quantitative performance of our optimized DIA workflow allow for the efficient simultaneous discovery and verification of biomarker candidates without the requirement for an early bias toward selected proteins.

Predictive value of C-reactive protein, ultrasound and Alvarado score in acute appendicitis: a prospective pediatric cohort

PURPOSE

To evaluate whether C-reactive protein (CRP) level and ultrasound (US) results on admission could aid the diagnostic accuracy of Alvarado score.

METHODS

A prospective study was performed on children <14 years admitted for suspected acute appendicitis. Patients were categorized into three groups based on the Alvarado score: group I: score 7-10, group II: score 5-6, group III: score 0-4.

RESULTS

The difference between predictive values of Alvarado score alone and Alvarado score with CRP was not statically significant. The PPV increased from 74.29% (Alvarado score and CRP) to 93.75% (Alvarado score and US) in group 1 (P = .001) and the NPV increased from 64.86 and 79.69% (Alvarado score and CRP) to 82.6 and 88.2% (Alvarado score and US) in group 2 (P = .01) and group 3 (P = .001), respectively.

CONCLUSIONS

Alvarado score and ultrasound taken together improve the predictive value of diagnosing acute appendicitis in children.

Development of metabolic and inflammatory mediator biomarker phenotyping for early diagnosis and triage of pediatric sepsis

Introduction

The first steps in goal-directed therapy for sepsis are early diagnosis followed by appropriate triage. These steps are usually left to the physician’s judgment, as there is no accepted biomarker available. We aimed to determine biomarker phenotypes that differentiate children with sepsis who require intensive care from those who do not.

Methods

We conducted a prospective, observational nested cohort study at two pediatric intensive care units (PICUs) and one pediatric emergency department (ED). Children ages 2–17 years presenting to the PICU or ED with sepsis or presenting for procedural sedation to the ED were enrolled. We used the judgment of regional pediatric ED and PICU attending physicians as the standard to determine triage location (PICU or ED). We performed metabolic and inflammatory protein mediator profiling with serum and plasma samples, respectively, collected upon presentation, followed by multivariate statistical analysis.

Results

Ninety-four PICU sepsis, 81 ED sepsis, and 63 ED control patients were included. Metabolomic profiling revealed clear separation of groups, differentiating PICU sepsis from ED sepsis with accuracy of 0.89, area under the receiver operating characteristic curve (AUROC) of 0.96 (standard deviation [SD] 0.01), and predictive ability (Q²) of 0.60. Protein mediator profiling also showed clear separation of the groups, differentiating PICU sepsis from ED sepsis with accuracy of 0.78 and AUROC of 0.88 (SD 0.03). Combining metabolomic and protein mediator profiling improved the model (Q² =0.62), differentiating PICU sepsis from ED sepsis with accuracy of 0.87 and AUROC of 0.95 (SD 0.01). Separation of PICU sepsis or ED sepsis from ED controls was even more accurate. Prespecified age subgroups (2–5 years old and 6–17 years old) improved model accuracy minimally. Seventeen metabolites or protein mediators accounted for separation of PICU sepsis and ED sepsis with 95 % confidence.

Conclusions

In children ages 2–17 years, combining metabolomic and inflammatory protein mediator profiling early after presentation may differentiate children with sepsis requiring care in a PICU from children with or without sepsis safely cared for outside a PICU. This may aid in making triage decisions, particularly in an ED without pediatric expertise. This finding requires validation in an independent cohort.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1026-2) contains supplementary material, which is available to authorized users.

Evaluation of urinary protein precipitation protocols for the multidisciplinary approach to the study of chronic pelvic pain research network

Standardization of sample collection, shipping, and storage has been a major focus of biorepositories servicing large, multi-institute studies. The standardization of total protein concentration measurements may also provide an important metric for characterizing biospecimens. The measurement of total protein concentration in urine is challenging because of widely variable sample dilutions obtained in the clinic and the lack of a reference matrix for use with a standard curve and blank subtraction. Urinary proteins are therefore typically precipitated and reconstituted in a reference solution before quantitation. We have tested three different methods for protein precipitation and evaluated them using variability in total protein concentration measurement as a metric. The methods were tested on four urine samples ranging from very concentrated to very dilute. A method using a commercially available kit provided the most reproducible results, with average coefficients of variation <10%. Addition of a freeze/thaw did not lead to significant protein loss or additional variability. Samples were titrated and the measurements obtained appeared to be linearly correlated with sample starting volume. This method was applied to analysis of 77 urine biorepository samples and provided reproducible results when the same sample was assayed on different microwell plates.

RNA Biosignatures in Adolescent Patients in a Pediatric Emergency Department With Pelvic Inflammatory Disease

BACKGROUND

Adolescents are at high risk for pelvic inflammatory disease (PID). Because accurate diagnosis of PID is difficult, and complications of untreated PID are significant, novel methods to improve diagnosis are essential.

OBJECTIVES

To determine if patients with PID have unique RNA expression patterns compared to controls.

METHODS

Peripheral blood was collected from adolescent females with PID in the emergency department, and from control patients in the operating room. RNA was isolated, and microarray analysis was performed. Initial analysis involved a training set of 18 patients (9 PID patients with either Neisseria gonorrhoeae or Chlamydia trachomatis infection and 9 control patients). Supervised and unsupervised cluster analyses were performed, followed by network analysis. The training set was used to classify a set of 15 additional PID patients and 2 controls.

RESULTS

Supervised cluster analysis of the training set revealed 170 genes which were differentially expressed in PID patients versus controls. Network analysis indicated that several differentially expressed genes are involved in immune activation. Analysis of additional PID patients based on the training set findings revealed that patients with positive testing for Trichomonas vaginalis partitioned with the PID group, whereas patients with no organism identified partitioned with both groups.

CONCLUSIONS

RNA sample collection from adolescents in the emergency department is feasible. Genes were identified which were differentially expressed in PID patients versus controls, many of which are involved in inflammation. Future studies should confirm the training set findings on a larger sample and may lead to improved accuracy of PID diagnosis.

Syringe-push membrane absorption as a simple rapid method of urine preparation for clinical proteomics

Background

The analysis of urinary proteome might reveal biomarkers of clinical value. However, current methods of urine preparation for down-stream proteomic analysis are complicated, time-consuming, and/or expensive. This study aims to develop a robust, simple, inexpensive and readily accessible urine preparation method to facilitate clinical proteomic workflow.

Result

Syringe-push membrane absorption (SPMA) was successfully developed by a combination of 5-ml medical syringe and protein-absorbable membrane. Comparing three membranes i.e., nitrocellulose, polyvinylidene difluoride (PVDF) and Whatman no.1, nitrocellulose combined with SPMA (nitrocellulose-SPMA) provided the greatest quality of proteome profile as demonstrated by 2-DE. The quality of the proteome profile and the performance of nitrocellulose-SPMA were systematically compared with three current methods of urine preparation (i.e., ultrafiltration, dialysis/lyophilization and precipitation). While different methods of urine preparation provided comparable proteome quality, nitrocellulose-SPMA had better working performance due to acceptable recovery yield, less workload, short working time, high accessibility and low unit cost. In addition, protein absorbed on nitrocellulose harvested from the SPMA procedure could be stored as a dried membrane at room temperature for at least 1-month without protein degradation or modification.

Conclusions

SPMA is a simple rapid method of preparing urine for downstream proteomic analysis. Because of it is highly accessible and has long storage duration, this technique holds potential benefit for large-scale multi-center research and future development of clinical investigation based upon urinary proteomic analysis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12014-015-9087-4) contains supplementary material, which is available to authorized users.

Influence of honeybee sting on peptidome profile in human serum

The aim of this study was to explore the serum peptide profiles from honeybee stung and non-stung individuals. Two groups of serum samples obtained from 27 beekeepers were included in our study. The first group of samples was collected within 3 h after a bee sting (stung beekeepers), and the samples were collected from the same person a second time after at least six weeks after the last bee sting (non-stung beekeepers). Peptide profile spectra were determined using MALDI-TOF mass spectrometry combined with Omix, ZipTips and magnetic beads based on weak-cation exchange (MB-WCX) enrichment strategies in the mass range of 1–10 kDa. The samples were classified, and discriminative models were established by using the quick classifier, genetic algorithm and supervised neural network algorithms. All of the statistical algorithms used in this study allow distinguishing analyzed groups with high statistical significance, which confirms the influence of honeybee sting on the serum peptidome profile. The results of this study may broaden the understanding of the human organism’s response to honeybee venom. Due to the fact that our pilot study was carried out on relatively small datasets, it is necessary to conduct further proteomic research of the response to honeybee sting on a larger group of samples.

Journal Club: the Alvarado score as a method for reducing the number of CT studies when appendiceal ultrasound fails to visualize the appendix in adults

OBJECTIVE. The purpose of this article is to evaluate the hypothesis that Alvarado scores of 3 or lower identify adult patients who are unlikely to benefit from CT after appendiceal ultrasound fails to show the appendix and is otherwise normal. MATERIALS AND METHODS. We identified 119 consecutive adults for whom the appendix was not seen on otherwise normal appendiceal sonography performed as the first imaging study for suspected appendicitis, who subsequently underwent CT within 48 hours, and whose data permitted retrospective calculation of admission Alvarado scores. Specific benefits of CT were defined as diagnoses of appendicitis or significant alternative findings, and specific benefits were compared between patients with Alvarado scores of 3 or less and 4 or higher. Significant alternative findings on CT were findings other than appendicitis that were treated with medical or surgical therapy during the admission or that were to be addressed during follow-up care. Diagnostic reference standards were discharge diagnoses, pathologic examinations, and clinical follow-up. RESULTS. No patients (0.0%, 0/49) with Alvarado scores 3 or lower had appendicitis, compared with 17.1% (12/70) of patients with Alvarado scores 4 or higher (p = 0.001), and CT showed neither appendicitis nor significant alternative findings in 85.7% (42/49) versus 58.6% (41/70) of these patients, respectively (p = 0.002). The rates of perforated appendicitis, as well as significant alternative CT findings, did not differ significantly. CONCLUSION. Adults with Alvarado scores 3 or lower who have nonvisualized appendixes and otherwise normal appendiceal sonography are at very low risk for appendicitis or significant alternative findings and therefore are not likely to benefit from CT.

Urine sample preparation in 96-well filter plates to characterize inflammatory and infectious diseases of the urinary tract

Urine has been an important body fluid source for diagnostic and prognostic biomarkers of diseases for a long time. Technological advances during the last two decades have enabled a fundamental shift from the discovery of candidate protein biomarkers using single-assay platforms to highly parallel liquid chromatography tandem mass spectrometry (LC-MS/MS)-based proteomic analysis platforms. MS/MS-based approaches such as multiple reaction monitoring (MRM) are also being used increasingly for targeted protein biomarker validation. In large part due to the fact that the majority of protein in voided urine is soluble, such studies have focused on the analysis of urine supernatants, whereas the pellets were discarded after centrifugal sedimentation. Urine sediments are of particular value in the analysis of urinary tract infections (UTI). The LC-MS/MS methods now have sufficient resolving power and sensitivity to survey metaproteomes--the entirety of proteins derived from multiple organisms that interact with each other in mutualistic or antagonistic fashion. Challenges of proteomic analysis of urine include the high dynamic range of protein abundance, high levels of protein post-translational modifications, and high quantities of natural protease inhibitors. Recently, a robust and scalable workflow that can parallelize the processing of multiple urinary supernatant and sediment samples was developed and validated in our lab. This method utilizes 96-well format filter-aided sample preparation (96FASP) strategy and was shown to successfully identify large numbers of proteins from urine samples. Processing 10-50 µg total protein in single experiment, LC-MS/MS with a Q-Exactive mass spectrometer resulted in more than 1,100 distinct human protein identifications from urine supernatants, and around 400 microbial and 1,400 human protein identifications from urine sediments. The surveys are a rich data resource not only for biomarker discovery but also to interrogate mechanisms of pathogenesis in the urinary system.

Dynamic changes of urinary proteins in focal segmental glomerulosclerosis model

Compare to blood, which has mechanisms to maintain homeostasis, urine is more likely to reflect changes in the body. As urine accumulates all types of changes, identifying the precise cause of changes in the urine proteome is challenging and crucial in biomarker discovery. To reduce the confounding factors to minimal, some studies used animal model resembling human diseases. This chapter highlights the importance of animal models and introduces a strategic research which focused on adriamycin-induced nephropathy. In this study, urine samples were collected at before adriamycin administration and days 3, 7, 11, 15, and 23 after, urinary proteins were profiled by LC-MS/MS. Of 23 changed proteins with disease development, 13 proteins were identified as stable in normal human urine, meaning that changes in these proteins are more likely to reflect disease. We think this stage-dependent dynamic changes of urine proteome in animal models will help to support the role of urine as key source in biomarker discovery especially in kidney diseases and help to identify corresponding biomarkers for clinical validation.

Effects of diuretics on urinary proteins

Biomarker is the measurable change associated with a physiological or pathophysiological process. Unlike blood which has mechanisms to keep the internal environment homeostatic, urine is more likely to reflect changes of the body. As a result, urine is likely to be a better biomarker source than blood. However, since the urinary proteome is affected by many factors, including diuretics, careful evaluation of those effects is necessary if urinary proteomics is used for biomarker discovery. The human orthologs of most of these 14 proteins affected are stable in the healthy human urinary proteome, and 10 of them are reported as disease biomarkers. Thus, our results suggest that the effects of diuretics deserve more attention in future urinary protein biomarker studies. Moreover, the distinct effects of diuretics on the urinary proteome may provide clues to the mechanisms of diuretics.

Diagnosing appendicitis: evidence-based review of the diagnostic approach in 2014

Introduction

Acute appendicitis is the most common abdominal emergency requiring emergency surgery. However, the diagnosis is often challenging and the decision to operate, observe or further work-up a patient is often unclear. The utility of clinical scoring systems (namely the Alvarado score), laboratory markers, and the development of novel markers in the diagnosis of appendicitis remains controversial. This article presents an update on the diagnostic approach to appendicitis through an evidence-based review.

Methods

We performed a broad Medline search of radiological imaging, the Alvarado score, common laboratory markers, and novel markers in patients with suspected appendicitis.

Results

Computed tomography (CT) is the most accurate mode of imaging for suspected cases of appendicitis, but the associated increase in radiation exposure is problematic. The Alvarado score is a clinical scoring system that is used to predict the likelihood of appendicitis based on signs, symptoms and laboratory data. It can help risk stratify patients with suspected appendicitis and potentially decrease the use of CT imaging in patients with certain Alvarado scores. White blood cell (WBC), C-reactive protein (CRP), granulocyte count and proportion of polymorphonuclear (PMN) cells are frequently elevated in patients with appendicitis, but are insufficient on their own as a diagnostic modality. When multiple markers are used in combination their diagnostic utility is greatly increased. Several novel markers have been proposed to aid in the diagnosis of appendicitis; however, while promising, most are only in the preliminary stages of being studied.

Conclusion

While CT is the most accurate mode of imaging in suspected appendicitis, the accompanying radiation is a concern. Ultrasound may help in the diagnosis while decreasing the need for CT in certain circumstances. The Alvarado Score has good diagnostic utility at specific cutoff points. Laboratory markers have very limited diagnostic utility on their own but show promise when used in combination. Further studies are warranted for laboratory markers in combination and to validate potential novel markers.

Usefulness of serum leucine-rich alpha-2 glycoprotein as a disease activity biomarker in patients with rheumatoid arthritis

Our study aimed to investigate whether serum leucine-rich alpha-2-glycoprotein (LRG) levels are elevated in patients with rheumatoid arthritis (RA). In addition, we assessed their correlation with disease activity parameters and pro-inflammatory cytokine, tumor necrosis factor-α (TNF-α). Our study included 69 patients with RA and 48 age- and sex-matched healthy controls. Serum concentrations of TNF-α and LRG were determined by enzyme-linked immunosorbent assay. Serum LRG concentrations were significantly elevated in patients with RA compared with those in healthy controls (30.8 ± 14.4 vs. 22.2 ± 6.1 ng/mL; P<0.001). In patients with RA, serum LRG levels were found to be correlated with disease activity score 28 (DAS28), erythrocyte sedimentation rate, and C-reactive protein levels (γ=0.671; γ=0.612; and γ=0.601, P<0.001, respectively), but not with serum TNF-α levels. Serum LRG levels in patients with an active disease status (DAS28≥2.6) were significantly higher than those in remission (DAS28<2.6) (36.45 ± 14.36 vs. 24.63 ± 8.81 ng/mL; P<0.001). Our findings suggest that serum LRG could contribute to the inflammatory process independent of TNF-α and it may be a novel biomarker for assessing inflammatory activity in patients with RA.

Dynamic changes of urinary proteins in a focal segmental glomerulosclerosis rat model

Background

In contrast to blood, which has mechanisms to maintain a homeostatic internal environment, urine is more likely to reflect changes in the body. As urine accumulates all types of changes, identifying the precise cause of changes in the urine proteome is challenging and crucial in biomarker discovery. To reduce the effects of both genetic and environmental factors on the urinary proteome, this study used a rat model of adriamycin-induced nephropathy resembling human focal segmental glomerulosclerosis (FSGS) development.

Results

Urine samples were collected at before adriamycin administration and day3, 7, 11, 15 and 23 after. Urinary proteins were profiled by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Of 23 changed proteins with disease development, 20 have human orthologs, and 13 proteins were identified as stable in normal human urine, meaning that changes in these proteins are more likely to reflect disease. Fifteen of the identified proteins have not been established to function in FSGS development. Seven proteins were selected for verification in ten more rats as markers closely associated with disease severity by western blot.

Conclusion

We identified proteins changed in different stages of FSGS in rat models, which may aid in biomarker development and the understanding of FSGS pathogenesis.

Urine sample preparation in 96-well filter plates for quantitative clinical proteomics

Urine is an important, noninvasively collected body fluid source for the diagnosis and prognosis of human diseases. Liquid chromatography mass spectrometry (LC-MS) based shotgun proteomics has evolved as a sensitive and informative technique to discover candidate disease biomarkers from urine specimens. Filter-aided sample preparation (FASP) generates peptide samples from protein mixtures of cell lysate or body fluid origin. Here, we describe a FASP method adapted to 96-well filter plates, named 96FASP. Soluble urine concentrates containing ~10 μg of total protein were processed by 96FASP and LC-MS resulting in 700-900 protein identifications at a 1% false discovery rate (FDR). The experimental repeatability, as assessed by label-free quantification and Pearson correlation analysis for shared proteins among replicates, was high (R ≥ 0.97). Application to urinary pellet lysates which is of particular interest in the context of urinary tract infection analysis was also demonstrated. On average, 1700 proteins (±398) were identified in five experiments. In a pilot study using 96FASP for analysis of eight soluble urine samples, we demonstrated that protein profiles of technical replicates invariably clustered; the protein profiles for distinct urine donors were very different from each other. Robust, highly parallel methods to generate peptide mixtures from urine and other body fluids are critical to increase cost-effectiveness in clinical proteomics projects. This 96FASP method has potential to become a gold standard for high-throughput quantitative clinical proteomics.

Deciphering the peptidome of urine from ovarian cancer patients and healthy controls

Background

Ovarian cancer (OvCa) is the most lethal gynecological malignancy. The emergence of high-throughput technologies, such as mass spectrometry, has allowed for a paradigm shift in the way we search for novel biomarkers. Urine-based peptidomic profiling is a novel approach that may result in the discovery of noninvasive biomarkers for diagnosing patients with OvCa. In this study, the peptidome of urine from 6 ovarian cancer patients and 6 healthy controls was deciphered.

Results

Urine samples underwent ultrafiltration and the filtrate was subjected to solid phase extraction, followed by fractionation using strong cation exchange chromatography. These fractions were analyzed using an Orbitrap mass spectrometer. Over 4600 unique endogenous urine peptides arising from 713 proteins were catalogued, representing the largest urine peptidome reported to date. Each specimen was processed in triplicate and reproducibility at the protein (69-76%) and peptide (58-63%) levels were noted. More importantly, over 3100 unique peptides were detected solely in OvCa specimens. One such promising biomarker was leucine-rich alpha-2-glycoprotein (LRG1), where multiple peptides were found in all urines from OvCa patients, but only one peptide was found in one healthy control urine sample.

Conclusions

Mining the urine peptidome may yield highly promising novel OvCa biomarkers.

Effects of three commonly-used diuretics on the urinary proteome

Biomarker is the measurable change associated with a physiological or pathophysiological process. Unlike blood which has mechanisms to keep the internal environment homeostatic, urine is more likely to reflect changes of the body. As a result, urine is likely to be a better biomarker source than blood. However, since the urinary proteome is affected by many factors, including diuretics, careful evaluation of those effects is necessary if urinary proteomics is used for biomarker discovery. Here, we evaluated the effects of three commonly-used diuretics (furosemide, F; hydrochlorothiazide, H; and spirolactone, S) on the urinary proteome in rats. Urine samples were collected before and after intragastric administration of diuretics at therapeutic doses and the proteomes were analyzed using label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS). Based on the criteria of P≤0.05, a fold change ≥2, a spectral count ≥5, and false positive rate (FDR) ≤1%, 14 proteins (seven for F, five for H, and two for S) were identified by Progenesis LC-MS. The human orthologs of most of these 14 proteins are stable in the healthy human urinary proteome, and ten of them are reported as disease biomarkers. Thus, our results suggest that the effects of diuretics deserve more attention in future urinary protein biomarker studies. Moreover, the distinct effects of diuretics on the urinary proteome may provide clues to the mechanisms of diuretics.

Proteomic Workflows for Biomarker Identification Using Mass Spectrometry - Technical and Statistical Considerations during Initial Discovery

Identification of biomarkers capable of differentiating between pathophysiological states of an individual is a laudable goal in the field of proteomics. Protein biomarker discovery generally employs high throughput sample characterization by mass spectrometry (MS), being capable of identifying and quantifying thousands of proteins per sample. While MS-based technologies have rapidly matured, the identification of truly informative biomarkers remains elusive, with only a handful of clinically applicable tests stemming from proteomic workflows. This underlying lack of progress is attributed in large part to erroneous experimental design, biased sample handling, as well as improper statistical analysis of the resulting data. This review will discuss in detail the importance of experimental design and provide some insight into the overall workflow required for biomarker identification experiments. Proper balance between the degree of biological vs. technical replication is required for confident biomarker identification.

Evaluation of the diagnostic accuracy of plasma markers for early diagnosis in patients suspected for acute appendicitis

OBJECTIVES

The main objective of this study was to evaluate the diagnostic accuracy of two novel biomarkers, calprotectin (CP) and serum amyloid A (SAA), along with the more traditional inflammatory markers C-reactive protein (CRP) and white blood cell count (WBC), in patients suspected of having acute appendicitis (AA). The secondary objective was to compare diagnostic accuracy of these biomarkers with a clinical scoring system and radiologic imaging.

METHODS

A total of 233 patients with suspected AA, presenting to the emergency department (ED) between January 2010 and September 2010, and 52 healthy individuals serving as controls, were included in the study. Blood was drawn and CP and SAA-1 concentrations were measured using enzyme-linked immunosorbent assay (ELISA). CRP and WBC concentrations were routinely measured and retrospectively abstracted from the electronic health record, together with physical examination findings and radiologic reports. The Alvarado score was calculated as a clinical scoring system for AA. Final diagnosis of AA was based on histopathologic examination. The Mann-Whitney U-test was used for between-group comparisons. Receiver operating characteristic (ROC) curves were used to measure the diagnostic accuracy for the tests and to determine the best cutoff points.

RESULTS

Seventy-seven of 233 patients (33%) had proven AA. Median plasma levels for CP and SAA-1 were significantly higher in patients with AA than in those with another final diagnosis (CP, 320.9 ng/mL vs. 212.9 ng/mL; SAA-1, 30 mg/mL vs. 0.6 mg/mL; p < 0.001). CRP and WBC were significantly higher in patients with AA as well. The Alvarado score was helpful at the extremes (<3 or >7). Ultrasound (US) had a sensitivity of 84% and a specificity of 94%. Computed tomography (CT) had a sensitivity of 100% and a specificity of 91%. The area under the ROC (95% confidence interval [CI]) was 0.67 (95% CI = 0.60 to 0.74) for CP, 0.76 (95% CI = 0.70 to 0.82) for SAA, 0.71 (95% CI = 0.64 to 0.78) for CRP, and 0.79 (95% CI = 0.73 to 0.85) for WBC. No cutoff points had high enough sensitivity and specificity to accurately diagnose AA. However, a high sensitivity of 97% was shown at 7.5 × 10(9) /L for WBC and 0.375 mg/mL for SAA.

CONCLUSIONS

CP, SAA-1, CRP, and WBC were significantly elevated in patients with AA. None had cutoff points that could accurately discriminate between AA and other pathology in patients with suspected AA. A WBC < 7.5 × 10(9) /L, with a low level of clinical suspicion for AA, can identify a subgroup of patients who may be sent home without further evaluation, but who should have available next-day follow-up.

Urine proteomics for discovery of improved diagnostic markers of Kawasaki disease

Kawasaki disease (KD) is a systemic vasculitis of unknown etiology. Absence of definitive diagnostic markers limits the accuracy of clinical evaluations of suspected KD with significant increases in morbidity. In turn, incomplete understanding of its molecular pathogenesis hinders the identification of rational targets needed to improve therapy. We used high-accuracy mass spectrometry proteomics to analyse over 2000 unique proteins in clinical urine specimens of patients with KD. We discovered that urine proteomes of patients with KD, but not those with mimicking conditions, were enriched for markers of cellular injury such as filamin and talin, immune regulators such as complement regulator CSMD3, immune pattern recognition receptor muclin, and immune cytokine protease meprin A. Significant elevations of filamin C and meprin A were detected in both the serum and urine in two independent cohorts of patients with KD, comprised of a total of 236 patients. Meprin A and filamin C exhibited superior diagnostic performance as compared to currently used markers of disease in a blinded case-control study of 107 patients with suspected KD, with receiver operating characteristic areas under the curve of 0.98 (95% confidence intervals [CI] of 0.97-1 and 0.95-1, respectively). Notably, meprin A was enriched in the coronary artery lesions of a mouse model of KD. In all, urine proteome profiles revealed novel candidate molecular markers of KD, including filamin C and meprin A that exhibit excellent diagnostic performance. These disease markers may improve the diagnostic accuracy of clinical evaluations of children with suspected KD, lead to the identification of novel therapeutic targets, and allow the development of a biological classification of Kawasaki disease.

Application of proteomics to cerebrovascular disease

While neurovascular diseases such as ischemic and hemorrhagic stroke are the leading causes of disability in the world, the repertoire of therapeutic interventions has remained remarkably limited. There is a dire need to develop new diagnostic, prognostic, and therapeutic options. The study of proteomics is particularly enticing for cerebrovascular diseases such as stroke, which most likely involve multiple gene interactions resulting in a wide range of clinical phenotypes. Currently, rapidly progressing neuroproteomic techniques have been employed in clinical and translational research to help identify biologically relevant pathways, to understand cerebrovascular pathophysiology, and to develop novel therapeutics and diagnostics. Future integration of proteomic with genomic, transcriptomic, and metabolomic studies will add new perspectives to better understand the complexities of neurovascular injury. Here, we review cerebrovascular proteomics research in both preclinical (animal, cell culture) and clinical (blood, urine, cerebrospinal fluid, microdialyates, tissue) studies. We will also discuss the rewards, challenges, and future directions for the application of proteomics technology to the study of various disease phenotypes. To capture the dynamic range of cerebrovascular injury and repair with a translational targeted and discovery approach, we emphasize the importance of complementing innovative proteomic technology with existing molecular biology models in preclinical studies, and the need to advance pharmacoproteomics to directly probe clinical physiology and gauge therapeutic efficacy at the bedside.

Serum leucine-rich alpha-2 glycoprotein is a disease activity biomarker in ulcerative colitis

BACKGROUND

Reliable biomarkers for monitoring disease activity have not been clinically established in ulcerative colitis (UC). This study aimed to investigate whether levels of serum leucine-rich alpha-2 glycoprotein (LRG), identified recently as a potential disease activity marker in Crohn's disease and rheumatoid arthritis, correlate with disease activity in UC.

METHODS

Serum LRG concentrations were determined by enzyme-linked immunosorbent assay (ELISA) in patients with UC and healthy controls (HC) and were evaluated for correlation with disease activity. Expression of LRG in inflamed colonic tissues from patients with UC was analyzed by western blotting and immunohistochemistry. Interleukin (IL)-6-independent induction of LRG was investigated using IL-6-deficient mice by lipopolysaccharide (LPS)-mediated acute inflammation and dextran sodium sulfate (DSS)-induced colitis.

RESULTS

Serum LRG concentrations were significantly elevated in active UC patients compared with patients in remission (P < 0.0001) and HC (P < 0.0001) and were correlated with disease activity in UC better than C-reactive protein (CRP). Expression of LRG was increased in inflamed colonic tissues in UC. Tumor necrosis factor alpha (TNF-α), IL-6, and IL-22, serum levels of which were elevated in patients with active UC, could induce LRG expression in COLO205 cells. Serum LRG levels were increased in IL-6-deficient mice with LPS-mediated acute inflammation and DSS-induced colitis.

CONCLUSIONS

Serum LRG concentrations correlate well with disease activity in UC. LRG induction is robust in inflamed colons and is likely to involve an IL-6-independent pathway. Serum LRG is thus a novel serum biomarker for monitoring disease activity in UC and is a promising surrogate for CRP.

Detection and diagnostic value of urine leucine-rich α-2-glycoprotein in children with suspected acute appendicitis

STUDY OBJECTIVE

Previously, we used a proteomics approach for the discovery of new diagnostic markers of acute appendicitis and identified leucine-rich α-2-glycoprotein (LRG) that was elevated in the urine of children with acute appendicitis and enriched in diseased appendices. Here, we sought to evaluate the diagnostic utility of enzyme-linked immunosorbent assay (ELISA) of urine LRG in a blinded, prospective, cohort study of children being evaluated for acute abdominal pain.

METHODS

Urine LRG concentration was measured with a commercially available LRG ELISA and selected ion monitoring mass spectrometry. Urine LRG test performance was evaluated blindly against the pathologic diagnosis and histologic grade of appendicitis.

RESULTS

Urine LRG was measured in 49 patients. Mean urine LRG concentration measured with commercial LRG ELISA was significantly elevated in patients with acute appendicitis but exhibited an interference effect. Direct measurements using selected ion monitoring mass spectrometry demonstrated that LRG was elevated more than 100-fold in patients with acute appendicitis compared with those without, with the receiver operating characteristic area under the curve of 0.98 (95% confidence interval 0.96 to 1.0). Among patients with acute appendicitis, elevations of urine LRG measured with ELISA and selected ion monitoring mass spectrometry correlated with the histologic severity of appendicitis.

CONCLUSION

Urine LRG ELISA allows for discrimination between patients with and without acute appendicitis but exhibits limited accuracy because of immunoassay interference. Direct measurements of urine LRG with selected ion monitoring mass spectrometry demonstrate superior diagnostic performance. Development of a clinical-grade urine LRG assay is needed to advance the diagnostic accuracy of clinical evaluations of appendicitis.