Circulating pregnancy-associated plasma protein a predicts outcome in patients with acute coronary syndrome but no troponin I elevation

Pregnancy-associated plasma protein-A levels in patients with acute coronary syndromes: comparison with markers of systemic inflammation, platelet activation, and myocardial necrosis

OBJECTIVES

The goal of this study was to determine the predictive value of pregnancy-associated plasma protein-A (PAPP-A) in patients with acute coronary syndromes (ACS).

BACKGROUND

Pregnancy-associated plasma protein-A is a zinc-binding matrix metalloproteinase abundantly expressed in eroded and ruptured plaques and may serve as a marker of plaque destabilization.

METHODS

In 547 patients with angiographically validated ACS and in a heterogeneous emergency room population of 644 patients with acute chest pain, respectively, PAPP-A as well as markers of myocardial necrosis (troponin T [TnT]), ischemia (vascular endothelial growth factor [VEGF]), inflammation (high-sensitivity C-reactive protein [hsCRP]), anti-inflammatory activity (interleukin [IL]-10), and platelet activation (soluble CD40 ligand [sCD40L]) were determined. Patients were followed for the occurrence of death or myocardial infarction.

RESULTS

In patients with ACS, elevated PAPP-A levels (>12.6 mIU/l) indicated an increased risk (odds ratio 2.44 [95% confidence interval (CI) 1.43 to 4.15]; p = 0.001). When the analysis was restricted to TnT-negative patients, PAPP-A still identified a subgroup of high-risk patients (odds ratio [OR] 2.72 [95% confidence interval (CI) 1.25 to 5.89]; p = 0.009). In a multivariable model, PAPP-A (OR 2.01; p = 0.015), sCD40L (OR 2.37; p = 0.003), IL-10 (OR 0.43; p = 0.003), and VEGF (OR 2.19; p = 0.018) were independent predictors. Prospective validation in patients with chest pain confirmed that PAPP-A levels reliably identify high-risk patients (adjusted OR 2.32 [95% CI 1.32 to 4.26]; p = 0.008). Patients negative for all three markers (TnT, sCD40L, and PAPP-A) were at very low cardiac risk (30 days: 3.0% event rate; no death).

CONCLUSIONS

The PAPP-A level as a marker of plaque instability is a strong independent predictor of cardiovascular events in patients with ACS. Simultaneous determination of biomarkers with distinct pathophysiological profiles appears to remarkably improve risk stratification in patients with ACS.

Circulating pregnancy-associated plasma protein A is not an early marker of acute myocardial infarction

OBJECTIVE

The purpose of this study was to assess whether serum levels of pregnancy-associated plasma protein A (PAPP-A) are elevated early in patients with acute myocardial infarction (AMI).

DESIGN AND METHODS

We measured serum levels of PAPP-A in 80 patients with AMI and in 80 age-matched healthy control subjects. The mean (+/-SEM) time from onset of symptoms to blood sampling was 6.3 +/- 2.8 h in the group with AMI.

RESULTS

The PAPP-A levels did not differ between the control group and the AMI group (1.24 +/- 0.07 vs. 1.29 +/- 0.02 mIU/l; P = 0.54).

CONCLUSIONS

Measurement of serum PAPP-A does not seem to be a useful early marker for AMI.

Molecular Distinction of Circulating Pregnancy-Associated Plasma Protein A in Myocardial Infarction and Pregnancy

Background: In the blood of pregnant women, pregnancy-associated plasma protein A (PAPP-A) is present as a covalent complex with the proform of eosinophil major basic protein (proMBP). Recently, increased serum concentrations of PAPP-A have been found in acute coronary syndromes (ACS). The aim of this study was to investigate whether the circulating PAPP-A in ACS is the same as that in pregnancy.

Methods: We developed two time-resolved immunofluorometric assays based on a relative epitope map constructed by the use of 17 monoclonal antibodies. One assay, which measured total PAPP-A, used two PAPP-A subunit-specific antibodies. The other assay, which measured PAPP-A/proMBP complex, used one proMBP subunit-specific antibody and one PAPP-A subunit-specific antibody. Serum samples from four patients with myocardial infarction (MI), three pregnant women in their first trimester, and one in her third trimester were fractionated by gel filtration on a Superose™ 6 precision column. The two assays were used to analyze fractions obtained by gel filtration as well as serum samples serially collected from four other MI patients.

Results: Pregnancy-related PAPP-A was eluted as a single peak with a molecular mass of ∼700 kDa, whereas ACS-related PAPP-A was also eluted as a single peak but with a molecular mass of ∼530 kDa. Pregnancy-related PAPP-A was detected equally by the two assays, whereas increased ACS-related PAPP-A was detected only by the assay for total PAPP-A.

Conclusions: Our results provide the first evidence that circulating ACS-related PAPP-A is different from circulating pregnancy-related PAPP-A in that it is not complexed with proMBP. These findings provide a solid foundation for the design of immunoassays to accurately measure atherosclerosis-associated plasma protein A in the circulation.

Biomarkers of cardiac disease

The challenge of medical practice today is to identify individuals who are at risk of developing disease, determine the severity of the disease and distinguish the responders from the nonresponders to therapy (individualized medicine). Advances in molecular genetics and biology have shifted the paradigm for identification of markers from large-scale epidemiologic studies to studies on genomic- and proteomic-based techniques. Consequently, a large number of biologic markers, referred to as biomarkers, are being identified and validated to serve for risk stratification, prognostication and individualization of therapy. Identification of biomarkers for cardiovascular diseases could also provide insight into the pathogenesis of the phenotype, which is fundamental for the development of specific therapies. The list of biomarkers for cardiovascular disease is expanding rapidly. Nonetheless, the field is in the early stages of evolution and large-scale clinical studies are required to validate the utility of newly identified biomarkers in diagnosis, risk stratification and treatment of cardiovascular diseases. Selected biomarkers for coronary atherosclerosis, acute coronary syndromes and heart failure are discussed in this review.

CDC/AHA Workshop on Markers of Inflammation and Cardiovascular Disease

Inflammation is a recognized key component of acute coronary syndromes. Such pathogenetic achievement has led to the use of inflammatory cells and proteins as prognostic markers in these syndromes. A number of markers have been proposed, including proinflammatory cytokines such as interleukin-6, interleukin-1RA, and tumor necrosis factor-α, adhesion molecules such as intracellular adhesion molecule-1 and vascular adhesion molecule-1 and markers of cell activation. Although all are of scientific interest, the clinical use of these markers is limited by their high cost, low availability, and unfavorable biological profile. Conversely, common markers of inflammation such as C-reactive protein (CRP), the prototypic acute phase protein, and to a lesser extent fibrinogen, have been proven to be reliable and important markers of risk in ischemic heart disease. CRP, in particular, has been found to be associated with short- and long-term prognosis in acute coronary syndromes, including ST-elevation myocardial infarction, and in stable angina, and to predict the risk of restenosis and major events, including death, after revascularization procedures. CRP has been consistently found to be independent from other risk factors and to have an incremental value beyond the common risk factors and biochemical markers of risk, including troponin. Whether CRP also should be used as a guide to therapy is still a matter of discussion that deserves further, properly designed studies.

Markers to define ischemia: are they ready for prime time use in patients with acute coronary syndromes?

Optimal treatment of patients who present with chest pain is predicated on accurate identification of those patients with a cardiac etiology of their discomfort. Serial troponins and electrocardiograms are very sensitive for the detection of myocardial infarction but they are insensitive for the detection of ischemia. There are many analytes that are being actively evaluated for routine use to facilitate the identification of patients with myocardial ischemia. At present, only one assay is US Food and Drug Administration-approved for the exclusion of ischemia; many other analytes are under clinical evaluation and are briefly reviewed. At present, none of these analytes are yet appropriate for routine clinical use.

Evaluation of pregnancy-associated plasma protein A as a prognostic indicator in acute coronary syndrome patients

BACKGROUND

Higher circulating concentrations of pregnancy-associated plasma protein A (PAPP-A), a potential proatherosclerotic metalloproteinase, have been associated with increased risk for acute coronary syndrome (ACS). Our goal was to determine the ability of circulating concentrations of PAPP-A to predict adverse events in patients presenting to the Emergency Department (ED) with symptoms of ACS.

METHODS

A total of 346 patients with symptoms of ACS were included in the study. Serum samples obtained immediately after enrollment were analyzed for PAPP-A and cardiac troponin T (cTnT). The occurrence of adverse events during a 30-day follow-up period was recorded, and receiver-operating characteristic (ROC) curve analysis was performed to evaluate the prognostic characteristics of PAPP-A and cTnT.

RESULTS

A total of 33 (9.5 %) patients developed adverse events during the follow up period. At a cut-off concentration of 0.22 mIU/l, PAPP-A was a predictor of adverse events with a sensitivity and specificity (95% C.I.) of 66.7% (48.2-82.0) and 51.1% (45.4-56.8), respectively. The sensitivity and specificity of cTnT were 51.5% (33.6-69.2) and 82.1% (77.4-86.2), respectively, using a 0.01-ng/ml cut-off value, which was obtained using ROC analysis.

CONCLUSIONS

PAPP-A appears to be a modest predictor of adverse events in patients presenting to the ED with ACS symptoms, being inferior to cTnT in predicting adverse events in an ED setting. PAPP-A appears to be as sensitive as cTnT, but it is less specific.

Increased Levels of Pregnancy-Associated Plasma Protein A Are Associated with Mortality in Hemodialysis Patients: Preliminary Results

Pregnancy-associated plasma protein A (PAPP-A) is a new prognostic indicator of acute coronary syndrome. This protein is elevated in hemodialysis (HD) patients and is closely related to inflammation and oxidative stress. The aim of our pilot study was to find out whether PAPP-A is related to mortality in HD patients. 40 HD patients in a stable clinical state (20 men and 20 women, mean age 69 +/- 12 years) were enrolled in the study and followed up for 20 months. PAPP-A was assessed immunochemically (TRACE method) in serum samples (before the HD session) at the beginning of the observation period. During the follow-up, 22 patients died, 15 of them due to cardiovascular events. PAPP-A levels were significantly higher in the patients who died, compared to living HD patients: 26.8 (21.6-36.8) vs. 20 (14.9-26.6) mU/l, p = 0.034. PAPP-A could also be a new prognostic marker in hemodialysis patients, probably due to its close association with cardiovascular risk. More extensive studies are required to confirm this hypothesis.

Pregnancy-Associated Plasma Protein A and Its Endogenous Inhibitor, the Proform of Eosinophil Major Basic Protein (proMBP), Are Related to Complex Stenosis Morphology in Patients With Stable Angina Pectoris

Background— The metalloproteinase pregnancy-associated plasma protein-A (PAPP-A) has been implicated in coronary plaque disruption. Its endogenous inhibitor, the proform of eosinophil major basic protein (proMBP), may also play a role in this process. Atheromatous plaque disruption often presents as complex angiographic lesions. We sought to assess whether PAPP-A, proMBP, and PAPP-A/ProMBP ratio are markers of angiographic plaque complexity in patients with chronic stable angina.

Methods and Results— We studied 396 stable angina patients (age 63±10 years, 230 men) of whom 289 had angiographically documented coronary artery disease (≥75% stenosis). All coronary stenoses ≥30% diameter reduction (n =531 in 322 patients) were assessed and classified as complex (n =228) or smooth (n =303) by previously validated criteria. PAPP-A, proMBP, and C-reactive protein (hs-CRP) serum levels were measured by ELISA. Patients with complex coronary stenoses had a significantly ( P <0.001) higher PAPP-A/proMBP ratio (3.1±1.2 versus 2.7±0.8×10 −3 ) and PAPP-A levels (5.9±1.6 versus 5.1±1.4 mIU/L) than those without. On univariate analysis, male gender ( P <0.001), age ( P <0.001), previous history of myocardial infarction ( P =0.013), reduced ejection fraction ( P <0.001), severe coronary artery disease ( P <0.001), aspirin treatment ( P <0.001), PAPP-A levels ( P <0.001), and PAPP-A/proMBP ratio ( P <0.001) were correlated with the number of complex stenoses. Multiple regression analysis showed that male gender, age, severe coronary artery disease, and PAPP-A/proMBP ratio were independent predictors of the number of angiographically complex stenoses.

Conclusions— In patients with stable angina, PAPP-A and PAPP-A/proMBP ratio are associated with angiographic plaque complexity.

Biochemical markers of cardiac diseases

This article reviews the current contribution of the determination of biochemical markers to clinical cardiology and discusses some important developments in this field. Biochemical markers play a pivotal role in the diagnosis and management of patients with acute coronary syndrome (ACS), as witnessed by the incorporation of cardiac troponins into new international guidelines for patients with ACS and in the redefinition of myocardial infarction. Despite the success of cardiac troponins, there is still a need for development of early markers that can reliably rule out ACS from the emergency room at presentation and detect myocardial ischemia also in the absence of irreversible myocyte injury. Under investigation are two classes of indicators: markers of early injury/ischemia and markers of coronary plaque instability and disruption. Finally, with the characterization of the cardiac natriuretic peptides, Laboratory Medicine is also assuming part in the assessment of cardiac function.