Calprotectin and platelet aggregation in patients with stable coronary artery disease

Circulating Levels of Calprotectin as a Biomarker in Patients With Coronary Artery Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Calprotectin, also known as MRP8/14, is generated by immune cells and is altered in several inflammatory diseases. Studies have assessed their levels in patients with coronary artery disease (CAD) and its subtypes (stable CAD and acute coronary syndrome [ACS]). Herein, we aimed to systematically investigate these associations through a systematic review and meta-analysis.

METHODS

A systematic search was conducted in four online databases, including PubMed, Scopus, Embase, and the Web of Science. Relevant studies were retrieved, screened, and extracted. Random-effect meta-analysis was performed for the calculation of standardized mean difference (SMD) and 95% confidence interval (CI). Blood calprotectin levels were compared between CAD patients and controls, as well as CAD subtypes.

RESULTS

A total of 20 studies were included in the systematic review and meta-analysis, comprising 3300 CAD patients and 1230 controls. Patients with CAD had significantly higher calprotectin levels (SMD 0.81, 95% CI 0.32-1.30, p < 0.01). Similarly, patients with ACS were reported to have higher levels compared to those with stable CAD. However, there was no significant difference in terms of blood calprotectin levels between stable CAD cases and healthy controls. Finally, studies have shown that calprotectin could be used as a diagnostic biomarker of CAD while also predicting major adverse events and mortality in these patients.

CONCLUSION

Based on our findings, calprotectin, as an inflammatory marker, could be used as a possible biomarker for patients with CAD and ACS. These suggest the possibility of pathophysiological pathways for this involvement and warrant further research on these associations as well as their clinical utility.

Calprotectin and periostin levels in periodontitis patients with coronary artery disease

OBJECTIVE

The aim of the study was to assess the effect of non-surgical periodontal therapy (NSPT) on periodontal and cardiac parameters as well as on the expression of calprotectin and periostin levels in periodontitis patients with and without coronary artery disease (CAD).

METHODS

Ninety subjects were categorised into three groups: Group H: periodontally and systemically healthy subjects, Group P: stage III grade B periodontitis subjects with no associated systemic diseases and Group P + CAD: stage III grade B periodontitis subjects diagnosed with CAD. Demographic, periodontal and cardiac parameters were recorded at baseline (0 day) and on the 180th day after NSPT. Gingival crevicular fluid was collected from all participants at baseline (0 day) and after the 180th day. Calprotectin and periostin expression were reassessed.

RESULTS

A significant increase in the levels of calprotectin (34.05 ± 11.72) was seen at baseline in the P + CAD group, whereas on the contrary, a decreased periostin (1.59 ± 0.41) was also noted at baseline. The study also showed a significant improvement in periodontal and cardiac parameters on the 180th day following NSPT.

CONCLUSION

Detection of calprotectin and periostin expression in GCF samples could represent a link to the association of periodontitis and CAD.

Platelets exacerbate cardiovascular inflammation in a murine model of Kawasaki disease vasculitis

Kawasaki disease (KD) is the leading cause of acquired heart disease among children. Increased platelet counts and activation are observed during the course of KD, and elevated platelet counts are associated with higher risks of developing intravenous immunoglobulin resistance and coronary artery aneurysms. However, the role of platelets in KD pathogenesis remains unclear. Here, we analyzed transcriptomics data generated from the whole blood of patients with KD and discovered changes in the expression of platelet-related genes during acute KD. In the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis, LCWE injection increased platelet counts and the formation of monocyte-platelet aggregates (MPAs), upregulated the concentration of soluble P-selectin, and increased circulating thrombopoietin and interleukin 6 (IL-6). Furthermore, platelet counts correlated with the severity of cardiovascular inflammation. Genetic depletion of platelets (Mpl-/- mice) or treatment with an anti-CD42b antibody significantly reduced LCWE-induced cardiovascular lesions. Furthermore, in the mouse model, platelets promoted vascular inflammation via the formation of MPAs, which likely amplified IL-1B production. Altogether, our results indicate that platelet activation exacerbates the development of cardiovascular lesions in a murine model of KD vasculitis. These findings enhance our understanding of KD vasculitis pathogenesis and highlight MPAs, which are known to enhance IL-1B production, as a potential therapeutic target for this disorder.

Further Insights into the Gut Microbiota of Cow's Milk Allergic Infants: Analysis of Microbial Functionality and Its Correlation with Three Fecal Biomarkers

Cow's milk allergy (CMA) is one of the most prevalent food allergies in children. Several studies have demonstrated that gut microbiota influences the acquisition of oral tolerance to food antigens at initial stages of life. Changes in the gut microbiota composition and/or functionality (i.e., dysbiosis) have been linked to inadequate immune system regulation and the emergence of pathologies. Moreover, omic sciences have become an essential tool for the analysis of the gut microbiota. On the other hand, the use of fecal biomarkers for the diagnosis of CMA has recently been reviewed, with fecal calprotectin, α-1 antitrypsin, and lactoferrin being the most relevant. This study aimed at evaluating functional changes in the gut microbiota in the feces of cow's milk allergic infants (AI) compared to control infants (CI) by metagenomic shotgun sequencing and at correlating these findings with the levels of fecal biomarkers (α-1 antitrypsin, lactoferrin, and calprotectin) by an integrative approach. We have observed differences between AI and CI groups in terms of fecal protein levels and metagenomic analysis. Our findings suggest that AI have altered glycerophospholipid metabolism as well as higher levels of lactoferrin and calprotectin that could be explained by their allergic status.

Within-person reproducibility of proteoforms related to inflammation and renal dysfunction

Protein biomarkers and microheterogeneity have attracted increasing attention in epidemiological and clinical research. Knowledge of within-person reproducibility over time is paramount to determine whether a single measurement accurately reflects an individual's long-term exposure. Yet, research investigating within-person reproducibility for proteoforms is limited. We investigated the reproducibility of the inflammatory markers C-reactive protein (CRP), serum amyloid A (SAA), and calprotectin (S100A8/9), and the renal function marker cystatin C (CnC) using a novel immuno-MALDI-TOF MS assay. Reproducibility, expressed as intraclass correlation coefficient (ICC), was calculated for 16 proteoforms using plasma samples of the Western Norway B Vitamin Intervention Trial (WENBIT) cohort collected 1-3 y apart from 295 stable angina pectoris (SAP) patients and 16 weeks apart from 38 subjects of the Intervention with Omega Fatty Acids in High-risk Patients with Hypertriglyceridemic Waist (OMEGA) trial with abdominal obesity but no other documented co-morbidities. ICCs for inflammatory markers were lower in WENBIT (CRP: 0.51, SAAt: 0.38, S100At: 0.31) compared to OMEGA subjects (CRP: 0.71, SAAt: 0.73, S100At: 0.48), while comparable for CnCt (WENBIT: 0.69, OMEGA: 0.67). Excluding SAP patients with elevated inflammation (CRP > 10 µg/ml) increased the ICC of SAAt to 0.55. Reduction of the time interval from 3 to 1 y in WENBIT group increased ICCs for all proteoforms. With a few exceptions ICCs did not differ between proteoforms of the same biomarker. ICCs were highest in OMEGA subjects with fair-to-good reproducibility for all markers. Reproducibility of SAA and S100A8/9 proteoforms in the WENBIT cohort was related to inflammation. This work will inform future clinical and epidemiological research which relies on single time point biomarker assessment to investigate inflammation and renal function.

A neutrophil signature is strongly associated with increased cardiovascular risk in gout

OBJECTIVE

To investigate the association between neutrophil activation and cardiovascular risk in gout patients. We hypothesize that neutrophil activation mediates inflammation and therefore takes part in atherogenesis in gout patients.

METHOD

Patient data were collected from 75 consecutive gout patients participating in the Reade gout cohort Amsterdam. Levels of neutrophil extracellular traps (NETs) and neutrophil activation (calprotectin and peroxidase activity) were analysed by ELISA and fluorimetry in plasma and compared with healthy controls. Markers of neutrophil activation were related to clinical markers of cardiovascular risk, including BMI, smoking, blood pressure, lipid profile and 10 year risk of cardiovascular mortality (EU-SCORE).

RESULTS

Increased levels of NETs were found in gout patients, although increased levels were not associated with cardiovascular risk. However, markers of neutrophil activation, including peroxidase activity correlated with waist:hip ratio (β = 0.33, P < 0.001), cholesterol ratio (β = 0.46, P < 0.005) and triglycerides (β = 0.60, P < 0.001) as well as the 10 year risk of cardiovascular mortality (β = 0.44, P = 0.001). Calprotectin levels were elevated in hypertension (P = 0.005) and diabetes (P = 0.02). Finally, gout patients with high levels of both peroxidase and calprotectin ('neutrophil activation signature') had a markedly elevated cardiovascular risk score (P = 0.001), with 68% of the patients having high cardiovascular risk (odds ratio 2.9, P = 0.03).

CONCLUSION

We demonstrated elevated levels of neutrophil activation markers, MPO and calprotectin in gout patients as compared with healthy controls. Of note, neutrophil activation markers were associated with several risk factors for cardiovascular disease, including hyperlipidaemia, hypertension and diabetes. Finally, the presence of a neutrophil activation signature was strongly associated with an increased 10 year risk of cardiovascular mortality. Further studies are needed to determine whether gout-specific factors and/or cardiovascular risk factors contribute to the elevated neutrophil activation observed in these patients.

Elevated Faecal Calprotectin in Patients with a Normal Colonoscopy: Does It Matter in Clinical Practice? A Retrospective Observational Study

Introduction

Faecal calprotectin (FC) is commonly used as a diagnostic tool for patients with gastrointestinal (GI) symptoms. However, there is uncertainty in daily clinical practice how to interpret an elevated FC in patients with a normal colonoscopy. We investigated if patients with a normal colonoscopy but with an elevated FC more often were diagnosed with a GI disease in a 3-year follow-up period.

Methods

Patients referred for colonoscopy (n = 1,263) to the Umeå University Hospital endoscopy unit between 2007 and 2013 performed a FC test (CALPRO^®) on the day before bowel preparation. A medical chart review was performed on all patients who had normal findings on their colonoscopy (n = 585, median age 64 years).

Results

Thirty-four percent of the patients (n = 202) with normal colonoscopy had elevated FC (>50 μg/g), and these patients were more frequently diagnosed with upper GI disease during the follow-up period than patients with normal FC levels (9.9 vs. 4.7%; p = 0.015). The upper GI diseases were mainly benign (i.e., gastritis). In a binary logistic regression analysis controlling for age, gender, nonsteroid anti-inflammatory drug use, and proton-pump inhibitor use, there was no difference for a new diagnosis of upper GI disease in the follow-up period (multivariate OR 1.70; 95% CI: 0.77-3.74). There was no difference in a new diagnosis of lower GI disease (6.4 vs. 5.2%; p = 0.545) or cardiovascular disease/death (multivariate OR 1.68; 95% CI: 0.83-3.42) in the follow-up period between patients with elevated versus normal FC levels.

Conclusions

In patients with a normal colonoscopy, a simultaneously measured increased FC level was not associated with an increased risk for significant GI disease during a follow-up period of 3 years.

Prognostic value of 12 novel cardiological biomarkers in stable coronary artery disease. A 10-year follow-up of the placebo group of the Copenhagen CLARICOR trial

OBJECTIVE

To assess if 12 novel circulating biomarkers, when added to 'standard predictors' available in general practice, could improve the 10-year prediction of cardiovascular events and mortality in patients with stable coronary heart disease.

DESIGN

The patients participated as placebo receiving patients in the randomised clarithromycin for patients with stable coronary artery disease (CLARICOR) trial at a random time in their disease trajectory.

SETTING

Five Copenhagen University cardiology departments and a coordinating centre.

PARTICIPANTS

1998 participants with stable coronary artery disease.

OUTCOMES

Death and composite of myocardial infarction, unstable angina pectoris, cerebrovascular disease and death.

RESULTS

When only 'standard predictors' were included, 83.4% of all-cause death predictions and 68.4% of composite outcome predictions were correct. Log(calprotectin) and log(cathepsin-S) were not associated (p≥0.01) with the outcomes, not even as single predictors. Adding the remaining 10 biomarkers (high-sensitive assay cardiac troponin T; neutrophil gelatinase-associated lipocalin; osteoprotegerin; N-terminal pro-B-type natriuretic peptide; tumour necrosis factor receptor 1 and 2; pregnancy-associated plasma protein A; endostatin; YKL40; cathepsin-B), which were all individually significantly associated with the prediction of the two outcomes, increased the figures to 84.7% and 69.7%.

CONCLUSION

When 'standard predictors' routinely available in general practices are used for risk assessment in consecutively sampled patients with stable coronary artery disease, the addition of 10 novel biomarkers to the prediction model improved the correct prediction of all-cause death and the composite outcome by <1.5%.

TRIAL REGISTRATION NUMBER

NCT00121550.

Prognostic value of serum calprotectin level in elderly diabetic patients with acute coronary syndrome undergoing percutaneous coronary intervention: A Cohort study

Patients with acute coronary syndrome (ACS) have an increased serum level of calprotectin. The purpose of present study was to analyze the prognostic significance of serum calprotectin levels in elderly diabetic patients underwent percutaneous coronary intervention (PCI) due to ACS.A total of 273 consecutive elderly diabetic patients underwent PCI for primary ACS were enrolled. Serum calprotectin levels were measured before PCI, and baseline clinical characteristics of all patients were collected. All patients were followed up at regular interval for major adverse cardiovascular events (MACEs) during 1 year after PCI. MACEs include cardiovascular death, nonfatal myocardial infarction, and target vessel revascularization (TVR). The predicting value of serum calprotectin for MACEs was analyzed by using univariate and multivariate analysis and receiver-operating characteristic curve (ROC).At the endpoint of this study, 47 patients of all 273 patients had MACEs. According to optimal cutoff value of calprotectin for predicting MACEs by ROC analysis, all patients were stratified into a high calprotectin group and a low calprotectin group. The incidence rate of MACEs and TVR in high calprotectin group was prominently higher than that in low calprotectin group (21.9% vs 11.5%, P = .02). In multivariable COX regression analysis adjusting for potential confounders, serum calprotectin level remains as an independent risk predictor of MACE (hazard ratio, 1.56; 95% confidence interval [CI]: 1.08-4.62; P = .01).In diabetic patients with a comorbidity of ACS, a high serum level of calprotectin is associated to a higher MACE rate after PCI.

Serum Calprotectin Levels and Outcome Following Percutaneous Coronary Intervention in Patients with Diabetes and Acute Coronary Syndrome

Background

A retrospective study of data from a prospective clinical registry was conducted to evaluate the prognostic role of serum calprotectin in patients with diabetes who underwent percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS).

Material/Methods

Data were retrieved for 273 patients with diabetes mellitus who underwent PCI for primary ACS in a single center. Serum calprotectin levels were measured before PCI. Baseline clinical data included the Global Registry of Acute Coronary Events (GRACE) risk score for ACS. All patients underwent regular follow-up for major adverse cardiovascular events (MACE) during 12 months after PCI, including target vessel revascularization (TVR), defined as the need for an unplanned repeat PCI or coronary artery procedure. The predictive value of serum calprotectin for MACE was analyzed by using univariate and multivariate analysis and receiver operating characteristic (ROC) curve analysis.

Results

At the final follow-up, 47 of the 273 patients studies experienced MACE. Optimal cutoff values for serum calprotectin levels predictive for MACE stratified patients into a high calprotectin group and a low calprotectin group. The incidence of MACE and TVR in the high calprotectin group was significantly greater than in the low calprotectin group (21.9% vs. 11.5%; P=0.02). Multivariate analysis, adjusted for confounders, showed that the serum level of calprotectin was an independent risk factor for MACE (HR, 1.56; 95% CI, 1.08–4.62; P=0.01).

Conclusions

In patients with diabetes and the co-morbidity of ACS, a high serum level of calprotectin was associated with a significantly increased risk for MACE following PCI.

Zinc Homeostasis in Platelet-Related Diseases

Zn2+ deficiency in the human population is frequent in underdeveloped countries. Worldwide, approximatively 2 billion people consume Zn2+-deficient diets, accounting for 1-4% of deaths each year, mainly in infants with a compromised immune system. Depending on the severity of Zn2+ deficiency, clinical symptoms are associated with impaired wound healing, alopecia, diarrhea, poor growth, dysfunction of the immune and nervous system with congenital abnormalities and bleeding disorders. Poor nutritional Zn2+ status in patients with metastatic squamous cell carcinoma or with advanced non-Hodgkin lymphoma, was accompanied by cutaneous bleeding and platelet dysfunction. Forcing Zn2+ uptake in the gut using different nutritional supplementation of Zn2+ could ameliorate many of these pathological symptoms in humans. Feeding adult rodents with a low Zn2+ diet caused poor platelet aggregation and increased bleeding tendency, thereby attracting great scientific interest in investigating the role of Zn2+ in hemostasis. Storage protein metallothionein maintains or releases Zn2+ in the cytoplasm, and the dynamic change of this cytoplasmic Zn2+ pool is regulated by the redox status of the cell. An increase of labile Zn2+ pool can be toxic for the cells, and therefore cytoplasmic Zn2+ levels are tightly regulated by several Zn2+ transporters located on the cell surface and also on the intracellular membrane of Zn2+ storage organelles, such as secretory vesicles, endoplasmic reticulum or Golgi apparatus. Although Zn2+ is a critical cofactor for more than 2000 transcription factors and 300 enzymes, regulating cell differentiation, proliferation, and basic metabolic functions of the cells, the molecular mechanisms of Zn2+ transport and the physiological role of Zn2+ store in megakaryocyte and platelet function remain elusive. In this review, we summarize the contribution of extracellular or intracellular Zn2+ to megakaryocyte and platelet function and discuss the consequences of dysregulated Zn2+ homeostasis in platelet-related diseases by focusing on thrombosis, ischemic stroke and storage pool diseases.

Arterial Thrombosis Is Accompanied by Elevated Mitogen-Activated Protein Kinase (MAPK) and Cyclooxygenase-2 (COX-2) Expression via Toll-Like Receptor 4 (TLR-4) Activation by S100A8/A9

BACKGROUND The aim of this study was to determine the involvement of S100A8/A9 in the development of arterial thrombosis. MATERIAL AND METHODS A total of 303 patients were enrolled in this study, with 110 having acute coronary syndrome (ACS) and 110 having coronary heart disease (CHD), and 83 subjects served as healthy blood donors. The concentrations of Toll-like receptor 4 (TLR-4), cyclooxygenase-2 (COX-2), and S100A8/A9 protein were determined in the sera of the participants and in peripheral blood mononuclear cells (PBMCs) derived from a rat carotid artery thrombosis model and in human aortic endothelial cells (HAECs). The mitogen-activated protein kinase (MAPK) inhibitor SB203580 and the TLR-4 blocker CLI-095 were used to investigate the role of the TLR-4-MAPK-COX2 signaling axis in thrombosis. RESULTS The levels of COX-2, TLR-4, and S100A8/A9 in the sera of patients with ACS and CHD were significantly higher than in healthy controls (P<0.05). S100A8/A9 expression was significantly correlated with TLR-4 and COX-2 in the ACS group and with TLR-4 in the CHD group. In the rat carotid thrombosis model, the expressions of TLR-4, COX-2, and p-p38 MAPK significantly increased until 14 days after thrombosis induction, whereas S100A8/A9 expression increased until day 7, but then decreased. Administration of SB203580 to rats reduced COX-2 expression in PBMCs after thrombosis induction, and incubation of HAECs with CLI-095 reduced their p-p38 MAPK and COX-2 response to S100A8/A9 stimulation. CONCLUSIONS S100A8/A9 is upregulated after blood vessel injury and is enhanced in combination with TLR-4 COX-2 induction via p38 MAPK activation.

Neutrophil gelatinase-associated lipocalin (NGAL) and cardiovascular events in patients with stable coronary artery disease

Inflammation is an important mediator in the pathogenesis of atherosclerosis. Neutrophil gelatinase-associated lipocalin (NGAL) is a small glycoprotein secreted by neutrophils. NGAL regulates the activity of matrix metalloproteinase-9, which plays a role in plaque instability. It has therefore been hypothesised that NGAL may modulate inflammation and promote the development and progression of atherosclerosis. Our aim was to assess the predictive value of plasma NGAL in a prospective cohort study of 876 high-risk patients with stable coronary artery disease (CAD). NGAL levels were measured using the NGAL Test^TM from BioPorto Diagnostics. Clinical follow-up was performed after a median of 3.1 years. The endpoint was a combination of non-fatal acute myocardial infarction (MI), cardiovascular death (CVD), or ischaemic stroke. The NGAL concentration was (median [25;75%]: 64.3 µg/L [51.3;81.4]). The area under the receiver operating characteristic curve (AUC) was 0.56 (95% confidence interval (CI): 0.49;0.64) for the diagnosis of the composite endpoint and 0.66 (95% CI: 0.56;0.75) after adding NGAL to high-sensitive C-reactive protein (hs-CRP), leucocyte count, interleukin-6 (IL-6), calprotectin, age, sex, body mass index (BMI), diabetes mellitus, smoking and creatinine. However, the AUC for hs-CRP, leucocyte count, IL-6, calprotectin, age, sex, BMI, diabetes mellitus, smoking and creatinine without NGAL was similar at 0.66 (95% CI: 0.56;0.76). NGAL alone had no predictive value with respect to the composite endpoint of non-fatal AMI, ischaemic stroke, or CVD in stable CAD patients. NGAL did not add any predictive value to the endpoint compared with existing inflammatory biomarkers and cardiovascular risk factors.

The influence of low-grade inflammation on platelets in patients with stable coronary artery disease

Inflammation is likely to be involved in all stages of atherosclerosis. Numerous inflammatory biomarkers are currently being studied, and even subtle increases in inflammatory biomarkers have been associated with increased risk of cardiovascular events in patients with coronary artery disease (CAD). Low-grade inflammation may influence both platelet production and platelet activation potentially leading to enhanced platelet aggregation. Thrombopoietin is considered the primary regulator of platelet production, but it likely acts in conjunction with numerous cytokines, of which many have altered levels in CAD. Previous studies have shown that high-sensitive C-reactive protein (CRP) independently predicts increased platelet aggregation in stable CAD patients. Increased levels of CRP, fibrinogen, interleukin-6, stromal cell-derived factor-1, CXC motif ligand 16, macrophage migration inhibitory factor, RANTES, calprotectin, and copeptin have been associated with increased risk of cardiovascular events in CAD patients. Additionally, some of these inflammatory markers have been associated with enhanced platelet activation and aggregation. However, CRP and other inflammatory markers provide only limited additional predictive value to classical risk factors such as smoking, blood pressure, and cholesterol levels. Existing data do not clarify whether inflammation simply accompanies CAD and increased production and aggregation of platelets, or whether a causal relationship exists. In this review, we provide a comprehensive overview of inflammatory markers in stable CAD with particular emphasis on platelet production, activation, and aggregation in CAD patients.

Coronary artery disease-associated genetic variants and biomarkers of inflammation

INTRODUCTION

Genetic constitution and inflammation both contribute to development of coronary artery disease (CAD). Several CAD-associated single-nucleotide polymorphisms (SNPs) have recently been identified, but their functions are largely unknown. We investigated the associations between CAD-associated SNPs and five CAD-related inflammatory biomarkers.

METHODS

We genotyped 45 CAD-associated SNPs in 701 stable CAD patients in whom levels of high-sensitivity C-reactive protein (hsRCP), interleukin-6, calprotectin, fibrinogen and complement component 3 levels had previously been measured. A genetic risk score was calculated to assess the combined risk associated with all the genetic variants. A multiple linear regression model was used to assess associations between the genetic risk score, single SNPs, and the five inflammatory biomarkers.

RESULTS

The minor allele (G) (CAD risk allele) of rs2075650 (TOMM40/APOE) was associated with lower levels of high-sensitivity C-reactive protein (effect per risk allele: -0.37 mg/l [95%CI -0.56 to -0.18 mg/l]). The inflammatory markers tested showed no association with the remaining 44 SNPs or with the genetic risk score.

CONCLUSIONS

In stable CAD patients, the risk allele of a common CAD-associated marker at the TOMM40/APOE locus was associated with lower hsCRP levels. No other genetic variants or the combined effect of all variants were associated with the five inflammatory biomarkers.

Predictors for major cardiovascular outcomes in stable ischaemic heart disease (PREMAC): statistical analysis plan for data originating from the CLARICOR (clarithromycin for patients with stable coronary heart disease) trial

BACKGROUND

The purpose of the predictors for major cardiovascular outcomes in stable ischaemic heart disease (PREMAC) study is exploratory and hypothesis generating. We want to identify biochemical quantities which-conditionally on the values of available standard demographic, anamnestic, and biochemical data-may improve the prediction of cardiovascular outcomes and/or death in patients suffering from stable ischaemic heart disease. The candidate biochemical quantities include N-terminal pro-B-type natriuretic peptide, YKL-40, osteoprotegerin, high-sensitive assay cardiac troponin T (hs-cTnT), pregnancy-associated plasma protein-A (PAPP-A), cathepsin B, cathepsin S, soluble TNF receptor 1 and 2, neutrophil gelatinase-associated lipocalin, endostatin, and calprotectin. As an extra objective, we also want to assess if skewness in these predictors may explain why the clarithromycin for patients with stable coronary heart disease (CLARICOR) trial found increased all-cause and cardiovascular (CV) mortality on a brief clarithromycin regimen compared with placebo.

METHODS

Baseline data were obtained from the hospital files at five cardiology clinics covering the Copenhagen area. The CLARICOR trial included data from 4372 stable coronary artery disease patients recruited among such patients alive and diagnosed with acute myocardial infarction or unstable angina pectoris during 1993 to 1999 in Copenhagen and randomised during October 1999 to April 2000 to the CLARICOR trial of 14 days clarithromycin versus placebo.Initial follow-up lasted for 2.6 years, during which outcomes were collected through hospital and death registries and assessed by an adjudication committee. Corresponding register data later showed to produce similar results. The adjudicated outcomes were therefore replaced and augmented by register data on outcomes to cover 10 years of follow-up. Biochemical marker data were obtained from analysis of serum from the CLARICOR bio-bank collected at randomisation and stored at -80° C.Using Cox proportional hazard method, we will identify among the candidate biochemical quantities those which are significant predictors when used alone and in combination with the standard predictors as defined in the present study.

DISCUSSION

Patients who became stable during the period 1993 to 1999 and died before October 1999 are missing. The data from the placebo patients are nevertheless useful to identify new prognostic biomarkers in patients with stable coronary artery disease, and data from both trial groups are useful to assess important potential skewness between randomised groups. However, due to the potential selection bias, we do not feel that it is advisable to try to rank identified biochemical predictors relative to each other nor to use the results for predictive purposes.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT00121550 Date of registration 13 July 2005Date of enrolment of first participant 12 October 1999.