Etiologic diagnosis of ischemic stroke subtypes with plasma biomarkers

Clinical application of blood biomarkers in cerebrovascular disease

Identifying a biomarker or panel of biomarkers of cerebral ischemia would have a major impact on the care of stroke patients by facilitating early management decisions and individualization of care. Biochemical surrogates of cerebral ischemia might also play an important role by identifying relevant pathways for novel therapeutic strategies and by facilitating early clinical trials in cerebrovascular disease. Serum biomarkers related to pathways of hemostasis, oxidation and inflammation, or alterations in glial and neuronal proteins, have been identified but none have been recommended for routine clinical use. This review describes the most promising biomarkers of cerebrovascular disease and the context and limitations in which they have been studied.

Sensitive and selective detection of free FXIII activation peptide: a potential marker of acute thrombotic events

Coagulation factor XIII (FXIII) stabilizes fibrin fibers and is therefore a major player in the maintenance of hemostasis. FXIII is activated by thrombin resulting in cleavage and release of the FXIII activation peptide (AP-FXIII). The objective of this study was to characterize the released AP-FXIII and determine specific features that may be used for its specific detection. We analyzed the structure of bound AP-FXIII within the FXIII A-subunit and interactions of AP-FXIII by hydrogen bonds with both FXIII A-subunit monomers. We optimized our previously developed AP-FXIII ELISA by using 2 monoclonal antibodies. We determined high binding affinities between the antibodies and free AP-FXIII and demonstrated specific binding by epitope mapping analyses with surface plasmon resonance and enzyme-linked immunosorbent assay. Because the structure of free AP-FXIII had been characterized so far by molecular modeling only, we performed structural analysis by nuclear magnetic resonance. Recombinant AP-FXIII was largely flexible both in plasma and water, differing significantly from the rigid structure in the bound state. We suggest that the recognized epitope is either occluded in the noncleaved form or possesses a structure that does not allow binding to the antibodies. On the basis of our findings, we propose AP-FXIII as a possible new marker for acute thrombotic events.

Biomarkers of hypercoagulability and inflammation in childhood-onset arterial ischemic stroke

OBJECTIVE

To test the hypothesis that acute elevations of biomarkers of hypercoagulability and inflammation are common in children with arterial ischemic stroke (AIS), particularly among etiologic subtypes that carry an increased risk of recurrent stroke.

STUDY DESIGN

In this prospective/retrospective institutional-based cohort study of acute childhood-onset AIS (n = 50) conducted between 2005 and 2009, D-dimer, factor VIII (FVIII) activity, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were serially evaluated at the time of clinical blood sampling. Patients were classified by stroke subtype as cardioembolic, moyamoya, non-moyamoya arteriopathy, or other.

RESULTS

Both D-dimer and CRP were frequently elevated in acute childhood-onset AIS and exhibited a decreasing trend with time. Acute D-dimer levels were significantly higher in cardioembolic AIS compared with noncardioembolic AIS (median, 2.04 microg/mL [range 0.54-4.54 microg/mL] vs 0.32 microg/mL [0.22-3.18 microg/mL]; P = .002). At an optimal threshold of > or = 0.50 microg/mL, the sensitivity and specificity of D-dimer for cardioembolic subtype were 78% and 79%, respectively.

CONCLUSIONS

Our findings identify D-dimer and CRP as candidate biomarkers for etiology and prognosis in childhood-onset AIS. Further studies should investigate the role of these and other biomarkers of hypercoagulability and inflammation in childhood-onset AIS.

Interpretation and use of natriuretic peptides in non-congestive heart failure settings

Natriuretic peptides (NPs) have been found to be useful markers in differentiating acute dyspneic patients presenting to the emergency department (ED) and emerged as potent prognostic markers for patients with congestive heart failure (CHF). The best-established and widely used clinical application of BNP and NT-proBNP testing is for the emergent diagnosis of CHF in patients presenting with acute dyspnea. Nevertheless, elevated NPs levels can be found in many circumstances involving left ventricular (LV) dysfunction or hypertrophy; right ventricular (RV) dysfunction secondary to pulmonary diseases; cardiac inflammatory or infectious diseases; endocrinology diseases and high output status without decreased LV ejection fraction. Even in the absence of significant clinical evidence of volume overload or LV dysfunction, markedly elevated NP levels can be found in patients with multiple comorbidities with a certain degree of prognostic value. Potential clinical applications of NPs are expanded accompanied by emerging reports regarding screening the presence of secondary cardiac dysfunction; monitoring the therapeutic responses, risk stratifications and providing prognostic values in many settings. Clinicians need to have expanded knowledge regarding the interpretation of elevated NPs levels and potential clinical applications of NPs. Clinicians should recognize that currently the only reasonable application for routine practice is limited to differentiation of acute dyspnea, rule-out-diagnostic-tests, monitoring of therapeutic responses and prognosis of acute or decompensated CHF. The rationales as well the potential applications of NPs in these settings are discussed in this review article.

Bioinformatics for protein biomarker panel classification: what is needed to bring biomarker panels into in vitro diagnostics?

A large number of biomarkers have been discovered over the past few years using proteomics techniques. Unfortunately, most of them are neither specific nor sensitive enough to be translated into in vitro diagnostics and routine clinical practice. From this observation, the idea of combining several markers into panels to improve clinical performances has emerged. In this article, we present a discussion of the bioinformatics aspects of biomarker panels and the concomitant challenges, including high dimensionality and low patient number and reproducibility.

Prognostic values of lesion volume and biochemical markers in ischemic and hemorrhagic stroke: a stereological and clinical study

PURPOSE

Our aim was to evaluate the relationship between lesion volume, serum level of biochemical markers, and clinical situation in ischemic and hemorrhagic stroke.

METHODS

MRI was obtained on 33 ischemic and 28 hemorrhagic strokes. The Cavalieri method was used to measure the volume. To evaluate neurological situation of the patients, we used the National Institutes of Health Stroke Scale (NIHSS) and Rankin Disability Scores at the first, third, seventh, and thirtieth days. We measured the level of leptin, high sensitivity C-reactive protein (hs-CRP), insulin, cortisol, fibrinogen, protein C, protein S, von Willebrand factor, D-dimer, Antitrombin III, and Factor VIII (F VIII) at the same time intervals.

RESULTS

In ischemic events, cortisol level at third and seventh days, and fibrinogen level at the first day were correlated with lesion volumes (r = 0.5, p = .02; r = 0.4, p = .02; r = 0.5, p = .005, respectively). In hemorrhagic events, only fibrinogen level was correlated with lesion volumes at third day (r = 0.6, p = .04). No significant differences were found among all these biochemical parameters, neurological situation (p > .05), and lesion volumes at all times.

CONCLUSION

In the prediction of stroke prognosis, lesion volume and all of the evaluated biochemical parameters are not deterministic factors.

Pragmatic classification of the causes of high D-dimer

Venous thromboembolism (VTE) remains the most common preventable cause of in-hospital death and D-dimer (DD) is one of the essential diagnostic tools for it. Each risk factor for VTE can raise DD and they are numerous: 24 listed in 2008 European Guidelines. Acute coronary syndrome and stroke increase DD concentration, too. Thus, all three most important causes of cardiovascular death are capable of raising DD. Recent evidence suggests DD as a sensitive marker also for acute aortic dissection. Many other processes may raise DD concentration: atrial fibrillation, congestive heart failure, disseminated intravascular coagulation, etc. The adequate DD interpretation is additionally important due to the frequent usage of the test (probably millions of times a year in the world). Simple and concise classification is much easier to remember and such one is suggested.

D-dimer, magnetic resonance imaging diffusion-weighted imaging, and ABCD2 score for transient ischemic attack risk stratification

BACKGROUND

We sought to determine whether measurement of D-dimer (DD) would improve risk stratification after transient ischemic attack (TIA).

METHODS

We enrolled 167 patients with acute TIA in a prospective observational study. DD was measured using rapid enzyme-linked immunosorbent assay. The primary outcome measure was a composite end point consisting of stroke or death within 90 days or the identification of a high-risk stroke mechanism requiring specific early intervention (defined as > or =50% stenosis in a vessel referable to symptoms or a cardioembolic source warranting anticoagulation).

RESULTS

The composite end point occurred in 41 patients (25%). A 50% or greater stenosis was found in 25 patients (15%), a cardioembolic source in 14 (8%), and clinical events in 8 (5 strokes, 3 deaths), 6 of whom also had a high-risk cause of TIA. ABCD(2) score was associated with outcome (P for trend = .017, c-statistic 0.63). DD levels did not differ based on outcome status (geometric mean 0.75 v 0.82 microg fibrinogen equivalent unit/mL, P = .56), and DD had little use for predicting outcome (c-statistic 0.57), even when combined with ABCD(2) score. Of 96 patients with early magnetic resonance imaging (MRI), 23% had diffusion-weighted imaging (DWI) abnormalities, and MRI DWI was predictive of outcome (c-statistic 0.76). The addition of MRI DWI to ABCD(2) improved predictive accuracy (c-statistic 0.83) compared with either alone.

CONCLUSIONS

Many patients with TIA have a high-risk mechanism (large vessel stenosis or cardioembolism) or will experience stroke/death within 90 days. Increasing ABCD(2) scores were associated with this composite end point. Measurement of DD did not provide additional prognostic information.

Stroke biomarkers: progress and challenges for diagnosis, prognosis, differentiation, and treatment

BACKGROUND

Stroke is a devastating condition encompassing a wide range of pathophysiological entities that include thrombosis, hemorrhage, and embolism. Current diagnosis of stroke relies on physician clinical examination and is further supplemented with various neuroimaging techniques. A single set or multiple sets of blood biomarkers that could be used in an acute setting to diagnosis stroke, differentiate between stroke types, or even predict an initial/reoccurring stroke would be extremely valuable.

CONTENT

We discuss the current classification, diagnosis, and treatment of stroke, focusing on use of novel biomarkers (either solitary markers or multiple markers within a panel) that have been studied in a variety of clinical settings.

SUMMARY

The current diagnosis of stroke remains hampered and delayed due to lack of a suitable mechanism for rapid (ideally point-of-care), accurate, and analytically sensitive biomarker-based testing. There is a clear need for further development and translational research in this area. Potential biomarkers identified need to be transitioned quickly into clinical validation testing for further evaluation in an acute stroke setting; to do so would impact and improve patient outcomes and quality of life.

Soluble forms of RAGE in internal medicine

The receptor for advanced glycation end-products (RAGE) and its ligands are intimately involved in the pathobiology of a wide range of diseases that share common features, such as enhanced oxidative stress, immune/inflammatory responses, and altered cell functions. Soluble forms of RAGE (sRAGE), including the splice variant endogenous secretory (es)RAGE, have been found circulating in plasma and tissues. Experimental data suggest that these isoforms may neutralize the ligand-mediated damage by acting as a decoy. Moreover, evidence is mounting to support a role for both sRAGE and esRAGE as biomarkers or endogenous protection factors against RAGE-mediated pathogenesis. In this review, we will focus on clinical and therapeutical implications arising from studies investigating the significance of soluble RAGE isoforms in several clinical settings, including cardiovascular disease, diabetes mellitus, hypercholesterolemia, chronic renal failure, immune/inflammatory diseases, pulmonary diseases, neurodegeneration, and cancer.

Molecular biomarkers in stroke diagnosis and prognosis

Serum biomarkers related to the cascade of inflammatory, hemostatic, glial and neuronal perturbations have been identifed to diagnose and characterize intracerebral hemorrhage and cerebral ischemia. Interpretation of most markers is confounded by their latent rise, blood-brain barrier effects, the heterogeneity of etiologies and the wide range of normal values, limiting their application for early diagnosis, lesion size estimation and long-term outcome prediction. Certain hemostatic and inflammatory constituents have been found to predict response to thrombolysis and worsening due to infarct progression and secondary hemorrhage, offering a potential role for improved treatment selection and individualization of therapy. Biomarkers will become increasingly relevant for developing targets for neuroprotective therapies, monitoring response to treatment and as surrogate end points for treatment trials.

Usefulness of natriuretic peptide testing for long-term risk assessment following acute ischemic stroke

Acute-phase levels of B-type natriuretic peptide (BNP) and the N-terminal fragment of the BNP prohormone (NT-pro-BNP) have been associated with mortality when measured in patients with an acute ischemic stroke; however, data regarding the longer-term value of NT-pro-BNP for long-term prognostication after ischemic stroke are limited. Two hundred sixteen patients (mean age 67 +/- 13 years) with acute ischemic stroke were seen 6 months after index admission at which time a structured evaluation including measurement of plasma NT-pro-BNP was performed. Patients were followed for 45 months, with all-cause mortality as the clinical end point. Median NT-pro-BNP concentration for the entire group was 147 pg/ml (10th to 90th percentiles 37 to 869). At follow-up 45 patients (21%) had died. NT-pro-BNP concentrations were significantly higher in decedents (308 pg/ml, 10th to 90th percentiles 74 to 2,279) than in the 171 survivors (132 pg/ml, 10th to 90th percentiles 35 to 570, p <0.001). Patients with NT-pro-BNP < or =147 pg/ml had a significantly improved survival rate on univariate analysis (p <0.001). In multivariate analysis after adjustment for age, stroke severity, heart and renal failures, levels of NT-pro-BNP were an independent predictor of mortality >6 months after stroke (adjusted hazard ratio 1.5, 95% confidence interval 1.1 to 1.9, p = 0.005). In conclusion, NT-pro-BNP concentrations measured during the stable phase after acute ischemic stroke are strongly predictive of long-term mortality.

Soluble receptor for advanced glycation end products: a new biomarker in diagnosis and prognosis of chronic inflammatory diseases

The formation of advanced glycation end products (AGEs) is a result of the non-enzymatic reaction between sugars and free amino groups of proteins. AGEs, through interacting with their specific receptor for AGEs (RAGE), result in activation of pro-inflammatory states and are involved in numerous pathologic situations. The soluble form of RAGE (sRAGE) is able to act as a decoy to avoid interaction of RAGE with its pro-inflammatory ligands (AGEs, HMGB1, S100 proteins). sRAGE levels have been found to be decreased in chronic inflammatory diseases including atherosclerosis, diabetes, renal failure and the aging process. The use of measuring circulating sRAGEs may prove to be a valuable vascular biomarker and in this review, we describe the implications of sRAGE in inflammation and propose that this molecule may represent a future therapeutic target in chronic inflammatory diseases.

RAGE: a novel biological and genetic marker for vascular disease

RAGE [receptor for AGEs (advanced glycation end-products)] plays an important role in the development and progression of vascular disease. Studies in cultured cells and small animal models of disease have clearly demonstrated that RAGE is central to the pathogenesis of vascular disease of the macro- and micro-vessels in both the diabetic and non-diabetic state. Emerging results from human clinical studies have revealed that levels of circulating soluble RAGE in the plasma may reflect the presence and/or extent of vascular disease state. Additionally, genetic variants of the RAGE gene (AGER in HUGO nomenclature) have been associated with vascular disease risk. Combining RAGE circulating protein levels and the presence of particular RAGE polymorphisms may be a useful clinical tool for the prediction of individuals at risk for vascular disease. Therapeutic intervention targeted at the RAGE gene may therefore be a useful means of treating pathologies of the vasculature.

Blood markers for the prognosis of ischemic stroke: a systematic review

BACKGROUND AND PURPOSE

The performance of validated prognostic clinical models in acute ischemic stroke might be improved by addition of data on blood biomarkers.

METHODS

We searched Medline and EMBASE from 1966 to January 2007 for studies of blood markers in patients with ischemic stroke and an assessment of outcome (death, disability, or handicap). We adopted several strategies to reduce bias.

RESULTS

Studies were generally small (median number of subjects, 85; interquartile range, 49 to 184). Few had evidence of a sample size calculation (7 of 82 [9%]) or reported blinding to whether patients had stroke (21 of 82 [26%]). Of the 66 studies reporting a measure of association, 10 did not adjust for age or stroke severity, 14 adjusted for age, 7 adjusted for severity, and 35 adjusted for both; 30% (20 of 66) used a data-dependent threshold to predict good or bad outcome. There was evidence of within-study reporting bias and publication bias. Cardiac markers showed the most consistent association with poor outcome.

CONCLUSIONS

Blood biomarkers might provide useful information to improve the prediction of outcome after acute ischemic stroke. However, this review showed that many studies were subject to bias. Although some markers had some predictive ability, none of the studies was able to demonstrate that the biomarker added predictive power to a validated clinical model. The clinical usefulness of blood biomarkers for predicting prognosis in the setting of ischemic stroke has yet to be established.

Plasma brain natriuretic peptide as a surrogate marker for cardioembolic stroke

Background

Cardioembolic stroke generally results in more severe disability, since it typically has a larger ischemic area than the other types of ischemic stroke. However, it is difficult to differentiate cardioembolic stroke from non-cardioembolic stroke (atherothrombotic stroke and lacunar stroke). In this study, we evaluated the levels of plasma brain natriuretic peptide in acute ischemic stroke patients with cardioembolic stroke or non-cardioembolic stroke, and assessed the prediction factors of plasma brain natriuretic peptide and whether we could differentiate between stroke subtypes on the basis of plasma brain natriuretic peptide concentrations in addition to patient's clinical variables.

Methods

Our patient cohort consisted of 131 consecutive patients with acute cerebral infarction who were admitted to Kagawa University School of Medicine Hospital from January 1, 2005 to December 31, 2007. The mean age of patients (43 females, 88 males) was 69.6 ± 10.1 years. Sixty-two patients had cardioembolic stroke; the remaining 69 patients had non-cardioembolic stroke (including atherothrombotic stroke, lacunar stroke, or the other). Clinical variables and the plasma brain natriuretic peptide were evaluated in all patients.

Results

Plasma brain natriuretic peptide was linearly associated with atrial fibrillation, heart failure, chronic renal failure, and left atrial diameter, independently (F_4,126 = 27.6, p < 0.0001; adjusted R² = 0.45). Furthermore, atrial fibrillation, mitral regurgitation, plasma brain natriuretic peptide (> 77 pg/ml), and left atrial diameter (> 36 mm) were statistically significant independent predictors of cardioembolic stroke in the multivariable setting (Χ² = 127.5, p < 0.001).

Conclusion

It was suggested that cardioembolic stroke was strongly predicted with atrial fibrillation and plasma brain natriuretic peptide. Plasma brain natriuretic peptide can be a surrogate marker for cardioembolic stroke.