N-terminal and C-terminal fragments of IGFBP-4 as novel biomarkers for short-term risk assessment of major adverse cardiac events in patients presenting with ischemia A.B. Postnikov a, ⁎ , 1 , T.I. Smolyanova a, 1 , A.V. Kharitonov a , D.V. Serebryanaya a , S.V. Kozlovsky a , Y.A. Tryshina b , R.V. Malanicev c , A.G. Arutyunov d , M.M. Murakami e , F.S. Apple e , A.G. Katrukha a a HyTest Ltd, Intelligate 6th floor, Joukahaisenkatu 6, 20520, Turku, Finland b School of Biology, Moscow State University, Leninskye gory 1/12, 119992, Moscow, Russian Federation c City Hospital #4, Pavlovskaya 25, 115093, Moscow, Russian Federation d Pirogov Russian State Medical University, Ostrovityanova 1/7, 117997, Moscow, Russian Federation e Hennepin County Medical Center and the University of Minnesota, Department of Laboratory Medicine and Pathology, Minneapolis, MN, USA abstract article info Article history: Received 17 October 2011 Received in revised form 8 December 2011 Accepted 27 December 2011 Available online 28 January 2012 Keywords: Myocardial infarction Biomarkers Major adverse cardiac events (MACE) Cardiovascular risk Prognosis Immunoassay Acute coronary syndrome Ischemia Pregnancy Associated Plasma Protein A (PAPP-A) IGFBP-4 fragments Objectives: Pregnancy Associated Plasma Protein A (PAPP-A)-derived N- and C-terminal fragments of IGF-binding protein-4 (NT- and CT-IGFBP-4) released from vulnerable atherosclerotic plaques are proposed to be used for cardiovascular risk assessment. Design and methods: NT- and CT-IGFBP-4 were measured by novel immunoassays in EDTA-plasma of 180 patients admitted to the emergency department with symptoms of myocardial ischemia but without ST-segment elevation. Six-month incidence of major adverse cardiac events (MACE), including myocardial infarction, cardiac death, percutaneous coronary interventions, and coronary artery bypass grafting was recorded. Results: Sixteen patients met the endpoint. NT- and CT-IGFBP-4 were strong predictors of MACE: area under ROC curve (AUC) 0.856 and 0.809, respectively. NT-IGFBP-4 concentrations ≥ 214 μg/L and CT-IGFBP- 4 concentrations ≥ 124 μg/L were associated with increased risk of future MACE: adjusted hazard ratio 13.79 and 7.93, respectively. Conclusions: IGFBP-4 fragments can be utilized as biomarkers for MACE prediction in patients with suspected myocardial ischemia. © 2012 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. Introduction The search for and development of novel biomarkers for the assess- ment of the risk of major adverse cardiac events (MACE) associated with atherosclerosis is one of the most urgent goals of current diagnos- tics. Methods such as imaging and ultrasound scanning are most often used in the investigations of atherosclerotic plaque pathophysiology. These methods are notable for high quality visual data that provides a reliable basis for the classification of atherosclerotic plaques according to its size, thickness of fibrous cap, levels of intraplaque necrosis and cal- cification. However, in spite of high accuracy in the description of instant parameters of atherosclerotic plaques, imaging methods have limited capability to assess the risk of plaque rupture and con- sequently to predict future MACE [1]. Numerous low-molecular weight molecules, proteins, and complex multicomponent particles have been analyzed as possible circulating biomarkers for atherosclerotic plaque destabilization and rupture [2], but none of these biomarkers were gen- erally acknowledged [3]. Such biomarkers could be important for reli- able risk assessment of patients admitted to the emergency department with symptoms of myocardial ischemia, could allow more effective use of therapeutic and surgical methods for MACE prevention. Pregnancy associated plasma protein A (PAPP-A) has been studied as a candidate biomarker of atherosclerotic plaque destabilization along with other proteins, such as lipoprotein-associated phospholipase A2 (Lp-PLA2), myeloperoxidase (MPO), and C-reactive protein (CRP) [4–9]. It was shown that expression of PAPP-A is significantly increased in unstable atherosclerotic plaques [10]. PAPP-A expressed in the unsta- ble atherosclerotic plaque consists of two identical subunits (dimeric PAPP-A or dPAPP-A), in contrast to the heterotetrameric form found in the blood of pregnant women where two PAPP-A subunits are complexed with two subunits of the proform of eosinophil major basic protein (proMBP) [11]. The role of dPAPP-A as a factor involved in the process of atherosclerotic plaque destabilization was demonstrat- ed in PAPP-A knockout and overexpression mouse models [12,13]. Clinical application of dPAPP-A as a biomarker is hampered by low levels of the analyte and by heparin injections, which influence Clinical Biochemistry 45 (2012) 519–524 ⁎ Corresponding author. E-mail address: Alexander.Postnikov@hytest.fi (A.B. Postnikov). 1 Both authors contributed equally to this work. 0009-9120/$ – see front matter © 2012 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. 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