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1 152 Available online at Annals of Clinical & Laboratory Science, vol. 45, no. 2, 2015 The Distribution of Abbott High-Sensitivity Troponin I Levels in Korean Patients with Chest Pain Kyunghoon Lee 1, Soo-Youn Lee 1, Jin-Oh Choi 2, Eun-Seok Jeon 2, and Hyung-Doo Park 1 1 Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, and 2 Division of Cardiology, Department of Medicine, Cardiac and Vascular Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea Abstract. Background. Troponin is considered a primary biomarker for coronary heart disease. We investigated the clinical utility of the Abbott high-sensitivity cardiac troponin I (hs-tni) assay in patients with various cardiac problems. Methods. Precision was investigated by ten levels of pooled sera and three levels of control materials. We determined Abbott hs-tni levels in a total of 3314 Korean patients with chest pain, including acute myocardial infarction (n=381), unstable angina (n=327), stable angina (n=1361), variant angina (n=189), non-coronary artery diseases (n=236), and nonspecific chest pain (n=820). The 99 th percentile cutoff was established by the plasma from the cardio-healthy subgroup and validated by 118 healthy individuals. Results. The total coefficient of variation in patient pooled sera and controls ranged from % and %, respectively. There was a significant difference in hs-tni among various cardiac problems: subjects with non-cardiac chest pain (median 1.7 pg/ml, 25%/75% quartile 1.1/2.8 pg/ml), variant angina (2.4 pg/ml,1.4/5.6 pg/ml), stable angina (3.7 pg/ml, 2.1/8.9 pg/ml), unstable angina (10.7 pg/ml, 3.7/61.7 pg/ml), and non-coronary artery diseases (9.3 pg/ml, 4.3/37.4 pg/ml). However, the median levels of hs-tni were not statistically different (p=0.921) between unstable angina and non-coronary artery diseases. The overall 99 th percentile cutoff was 19.3 pg/ml (range pg/ ml). Conclusions. This new hs-tni assay may be helpful in determining a differential diagnosis in patients with chest pain. Key words: 99 th percentile, Chest pain, High-sensitivity troponin I, Korean Introduction Cardiac troponin (ctn) is the preferred biomarker for detecting acute myocardial injury and infarction. ctn is more sensitive and more tissue-specific compared to other biomarkers, including CK-MB, myoglobin, lactate dehydrogenase, and others [1,2]. A global task force with joint leadership among the European Society of Cardiology (ESC), the American College of Cardiology Foundation (ACCF), the American Heart Association (AHA), and the World Heart Federation (WHF) refined past criteria for myocardial infarction (MI) with a universal definition supporting the use of ctni as a preferred biomarker for myocardial injury [3]. The updated third universal definition of MI recommends diagnosis by detection of a typical change in cardiac biomarkers (preferably ctn) with at least one value exceeding the 99 th percentile cutoff, Address correspondence to Hyung-Doo Park, M.D., Ph.D.; Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, , Republic of Korea; phone: ; fax: ; e mail: nayadoo@hanmail.net along with evidence of MI consisting of at least one of the following: ischemic symptoms, pathological Q waves on ECG, ischemic ECG changes, left bundle branch block, imaging evidence of new loss of viable myocardium, new regional wall motion abnormality, or angiographic finding of intracoronary thrombus. It is recommended that acceptable imprecision and coefficient of variation (CV) at the 99 th percentile should be defined as 10% [3]. The major limitation of contemporary cardiac troponin assays is low sensitivity at presentation, especially in early presenters. To overcome this limitation, a high-sensitivity troponin (hs-tn) assay that conforms to the guidelines for the diagnosis of acute MI has been introduced [4]. Hs-Tn assays can measure concentrations above the standard assay s limit of detection for at least 50% of the healthy population, which is not possible with most contemporary ctn assays. Several hs-tn assays showed better precision at lower concentrations of 99 th percentile than ctn assays [5]. In comparison with the same manufacturer s previous ctn assay, /15/ by the Association of Clinical Scientists, Inc.

2 Hs-TnI in Koreans with chest pain 153 Table 1. Characteristics of hs-tni distributed patients Cardio-healthy Variant Stable Unstable Valvular heart Cardiomyopathies* Acute myocardial Angina Angina angina disease infarction N Age (20-71) (25-77) (32-89) (34-87) (40-84) (23-94) (30-96) No. of females (%) (35.8%) (14.3%) (27.3%) (33.6%) (43.0%) (30.3%) (24.4%) Creatinine (mg/dl) ( ) ( ) (0.40~13.26) ( ) ( ) ( ) ( ) NT-proBNP (pg/ml) (5-179) (6-2491) ( ) ( ) ( ) ( ) ( ) CRP (mg/dl) ( ) ( ) ( ) ( ) ( ) ( ) ( ) HbA1c (%) ( ) ( ) ( ) ( ) ( ) ( ) ( ) *Includes hypertrophic cardiomyopathy (HCMP) (n=13), hypertrophic cardiomyopathy dilated cardiomyopathy (DCMP) (n=45), ischemic cardiomyopathy (ICMP) (n=52), and stress-induced cardiomyopathy (SCMP) (n=12). All values except the number of patients and sex are median (range). the new hs-tn assay was able to more reliably measure lower concentrations [6]. In published studies, troponin has been detected in the majority of healthy populations with hs-tn assays, suggesting that low concentrations of troponin may be physiological [7,8]. Therefore, troponin may be considered a primary prevention biomarker and can be included as a risk factor for coronary heart disease just like smoking, hypertension, and hyperlipidemia [9]. Accordingly, it is of interest to determine the range of ctn in large populations and to evaluate the physiologic distribution of hs- Tn values using this new, highly sensitive assay. In this study, we investigated the clinical utility of the Abbott hs-tni assay in patients with various cardiac problems. Material and Methods From 2005 to 2007, a total of 3314 patients admitted with chest pain to the emergency department or the outpatient clinic at Samsung Medical Center were recruited for this study. Final adjudication was performed by expert cardiologists based primarily on imaging findings, including assessment of coronary status, cardiac morphology, and cardiac function. Cardiologists used clinical findings and routine cardiac markers (contemporary ctni, CK-MB, and myoglobin) to decide to do imaging assessment. All patients underwent coronary angiography and 46% had an echocardiogram. For patients from the emergency department, coronary angiography was performed within two hours of admission. Of the whole group, 820 patients were sorted into the non-cardiac chest pain group and had no signs of coronary stenosis, structural cardiac abnormality, or other cardiac diseases. The other 2494 patients were diagnosed with either acute MI (AMI, n=381), unstable angina (n=327), stable angina (n=1361), variant angina (n=189), or non-coronary artery diseases (n=236). The latter group consisted of patients with valvular heart diseases (VHD, n=114), hypertrophic cardiomyopathies (HCMP, n = 13), dilated cardiomyopathies (DCMP, n=45), ischemic cardiomyopathies (ICMP, n=52), and stress-induced cardiomyopathies (SCMP, n=12) (Table 1). The most frequent diagnosis was stable angina (41.1%). Informed consent was obtained from all patients before coronary angiography, and the study was approved by the local institutional review board. From the non-cardiac chest pain group, 544 subjects (349 males and 195 females; mean age ± standard deviation: 56±10 years) were selected to establish the 99 th percentile cutoff (Figure 1). The cutoff was analyzed using a nonparametric approach according to the Clinical and

3 154 Annals of Clinical & Laboratory Science, vol. 45, no. 2, 2015 Figure 1. Inclusion and exclusion criteria for the selection of patients with various cardiac diseases. Laboratory Standards Institute (CLSI) Protocol C28- A3c [10]. The method of percentile estimation was based on first ranking the hs-tni results and then obtaining the 90% confidence interval (CI) for the 99 th percentile cutoff. These patients had normal concentrations of serum creatinine, C-reactive protein (CRP), and N-terminal pro-brain natriuretic peptide (NT-proBNP). They had no previous history of cardiac disease or recurrent chest pain. Subjects who had abnormal serum creatinine, CRP, NT-proBNP, and a history of non-cardiac diseases (e.g., essential hypertension, lung diseases, cancers, sepsis, and muscular disorders) were excluded. The 99 th percentile cutoff was validated on the serum samples obtained from 118 healthy subjects (64 males and 54 females; 50±10 years) who visited a healthcare center for a regular check-up. All selected subjects had normal electrocardiograms and routine laboratory findings. Heparinized plasma samples (n=3314) were collected from the patients with chest pain. Samples were immediately separated from blood cells by centrifugation and stored as 0.5-mL aliquots at -70 C until the start of the study. Prior to the assay, each aliquot was thawed at room temperature, mixed, and re-centrifuged at 10,000 g. For validation of the 99 th percentile limit, fresh serum samples from healthcare center visitors were analyzed within four hours of collection. We used a prototype Architect STAT hs-tni assay (Abbott Diagnostics, Chicago, IL, USA) on an Abbott ARCHITECT i2000sr analyzer. Reagents for the hs-tni assay were provided by Abbott Diagnostics. The manufacturerclaimed limit of detection (LoD), 99 th percentile, and 10% CV concentration were 1.2 pg/ml, 16 pg/ml (CV 5.6%), and 3.0 pg/ml, respectively [5]. Based on the Gutenberg Health study [11], LoD was 3.4 pg/ml (range 0-50,000 pg/ml), and 10% CV concentration was 5.2 pg/ml. A precision study was performed according to the CLSI Protocol EP15-A2 [12]. Ten serum pools (levels 1-10) were prepared by pooling fresh sera from the patients. Level 10 pooling sera were diluted with 0.9% normal saline. Each pool was tested in four replicates daily for five days. The total %CVs were calculated and plotted against the mean concentration. The median values of the increased hs-tni concentration in AMI patients were compared with those of non-ami patients. The Mann-Whitney test was applied. A p-value of less than 0.05 was considered statistically significant. Statistical analyses were performed using MedCalc software 11.5 (Mariakerke, Belgium) and SPSS software 19.0 (Chicago, IL, USA). Median values and the 25 th and 75 th percentile values of hs-tni were calculated for all patient groups according to their disease status. Results The within-run CVs and total CVs in patient pooled sera ranged from % and %, respectively, at concentrations ranging from 8.6 (level 1) to pg/ml (level 10) (Table 2). The within-run CVs and total CVs in three control materials ranged from % and %, respectively. The CV was less than 10% at the 99 th percentile level of 19.3 pg/ml. The median hs-tni concentration in patients with AMI was greater than the median concentration in non-ami patients (2064 pg/ml vs. 4.6 pg/ml; p<0.001) with 25 th /75 th percentile values of 250/10,326 pg/ml versus 2.1/21.9 pg/ml, respectively. Figure 2 shows the median admission hs- TnI values by cardiac disease state. Healthy individuals showed a median hs-tni level of 1.5 pg/ ml. Subjects with non-cardiac chest pain showed lower levels of hs-tni (median 1.7 pg/ml, 25%/75% quartiles 1.1/2.8 pg/ml) compared to those with variant angina (2.4 pg/ml,1.4/5.6 pg/ ml). The patients with stable angina had a higher

4 Hs-TnI in Koreans with chest pain 155 Table 2. Precision results of the Architect hs-tni assay for ten patient pools and three control materials. Architect hs-tni assay Level N Mean (pg/ml) SD (pg/ml) CV (%) Within-run Total Patient pool Control materials Low Medium High median level of hs-tni (3.7 pg/ml, 2.1/8.9 pg/ ml) than subjects with non-cardiac chest pain (p<0.001). The patients with unstable angina (10.7 pg/ml, 3.7/61.7 pg/ml) and non-coronary artery diseases (9.3 pg/ml, 4.3/37.4 pg/ml) showed significantly higher hs-tni levels than those with variant angina or stable angina. However, the median levels of hs-tni were not statistically different (p=0.921) between subjects with unstable angina and those with non-coronary artery diseases. The 99 th percentile level was determined to be 19.3 pg/ml (90% CI pg/ml; Figure 3). The 99 th percentile cutoff level was 25.0 pg/ml (90% CI pg/ml) with a range of pg/ ml for males and 19.3 pg/ml (90% CI not applicable) with a range of pg/ml for females. Hs-TnI was detectable in all 544 samples from the non-cardiac chest pain population (100%), ranging from 0.2 to 30.6 pg/ml. In the validation set from healthy subjects, all subjects had a measurable hs-tni concentrations ranging from 0.1 to 19.0 pg/ml. Discussion The 99 th percentile limit was determined to be 19.3 pg/ml, lower than contemporary ctni assays including the ARCHITECT STAT TnI assay (28 pg/ml) [13-16]. As in previous studies, there was a statistically significant difference in the 99 th percentile limits by sex, with higher ctni in males than in females [6,7,17]. Compared with previous studies of the Abbott ARCHITECT hs-tni assay, our overall 99 th percentile was relatively low. According to the IFCC working group on the standardization of troponin I, a sample size of at least 300 individuals per group is required [18]. Therefore, this study has limitations because of insufficient female samples. Recommendations for defining a normal reference population were suggested, including clinical history, surrogate biomarkers, imaging modality and sufficient sample size are required to screen normal individuals [18]. The CV at the 99 th percentile level was less than 10% with this new hs-tni assay. Current guidelines recommend that the diagnostic threshold for acute MI should be the 99 th percentile of troponin levels in a healthy population with a 10% total CV at this level [19-21]. Most contemporary ctni assays, except for one, have not been able to achieve this recommendation at the 99 th percentile cutoff [5,14,15,22,23]. In one study, all participating ctni assays (n=15) failed to achieve an imprecision of 10% at their respective 99 th percentile cut-off levels. The level at which 10% CV was achieved ranged from approximately two- to four-times the 99 th percentile cutoff [22]. As newer hs-tni or hs- TnT assays become available, more sensitive and stable measurements are possible. Significantly lower concentrations of TnI can even be detected in a healthy population by high-sensitivity troponin assays [6].

5 156 Annals of Clinical & Laboratory Science, vol. 45, no. 2, 2015 high-sensitivity troponin assays, troponin can be detected in patients with transient ischemic or inflammatory myocardial injury [24,25] because these conditions also cause myocyte necrosis. Elevated troponin may be detected in conditions other than acute coronary syndrome, particularly in cardiac conditions like heart failure, cardiomyopathies, myocarditis, arrhythmias, and pulmonary embolism, and even after exercise in healthy individuals [24,26]. Figure 2. Hs-TnI distribution in patient groups with various cardiac conditions. The horizontal dashed line indicates the 99 th percentile cutoff (19.3 pg/ml). The boxplot graph indicates 25% quartile, median, 75% quartile. The bar indicates the smallest and largest. The median hs-tni concentration of each group is noted in the right side of the box plot. Non-coronary artery diseases consist of valvular heart disease (VHD), hypertrophic cardiomyopathy (HCMP), hypertrophic cardiomyopathy dilated cardiomyopathy (DCMP), ischemic cardiomyopathy (ICMP), and stress-induced cardiomyopathy (SCMP). Figure 3. Distribution of hs-tni concentrations in 544 cardiohealthy subjects: the 99th percentiles presented for a total of 544 plasma samples (A), 349 plasma samples of males (B), and 195 plasma samples of females (C). We found that there was a significant difference in hs-tni among patient groups with various cardiac diseases. About one-third of patients with unstable angina or non-coronary artery disease had elevated values. These patients need to be differentiated from AMI patients with ctni elevation. Thus, serial measurements are needed to detect a rise and/or fall in TnI over time. Before the development of hs-ctn assays, troponins did not appear in conditions other than AMI. Circulation of cardiac troponin was considered to be indicative of myocardial necrosis. With Patients with myocarditis and cardiomyopathy also presented with higher hs-tni levels at admission. Further evaluation with echocardiography and coronary angiography may be needed to make a more precise diagnosis. Previous studies reported an increase of ctni levels in diffuse myocarditis, ischemic heart disease (IHD), and DCMP patients [25]. Frankenstein et al. showed that 71% (12/17) of patients with IHD and 33% (8/24) of patients with DCMP had hs-tnt levels above the 99th percentile of the assay used [27]. Stress-induced cardiomyopathy (Takotsubo cardiomyopathy) is characterized by symptoms mimicking AMI combined with troponin elevation [28,29]. The median hs-tni level of patients with unstable angina was statistically higher than that of patients with stable angina, which is consistent with the study by Keller et al., which showed that 240 unstable angina patients had a median hs-tni level of 90 pg/ml at the time of admission [11]. In this study, the majority of patients with chest pain and positive cardioangiographic findings were diagnosed with stable angina. Stable angina is known to be the most common cause of chest pain in emergency departments [30]. Korosoglou et al. showed that 23% of patients (29/124) with stable angina had an hs-tnt level above 14 pg/ml [31]. They suggested that the chronically silent rupture of non-calcified plaques with subsequent microembolization may be a source of troponin elevation observed in patients with stable angina [31]. One of the strengths of our study was the ability to assess coronary artery status through coronary catheterization in a large group of chest pain patients. We found that the hs-tni level was statistically different in various cardiac disease population. Females comprised 36% of the cardio-healthy group and this lower percentage may have influenced the

6 overall 99 th percentile cutoff. Interestingly, the 99 th percentile limit of the overall group was the same as that of the female subjects. Unexpectedly, no pool had an imprecision greater than 10% with the use of 10 serum pools for the precision profile. Therefore, we were unable to establish a concentration with either 10% or 20% of total CV. In summary, the performance of the prototype hs- TnI assay on the Abbott ARCHITECT meets guidelines, with the 10% CV value below the 99 th percentile limit, and can aid in differentiating patients with various cardiac diseases. Acknowledgment We thank Abbott Diagnostics for the reagents, calibrators, and controls used in this study. The kindness of Dr. Haiyoung Jung for critically reading the manuscript is also greatly appreciated. References 1. Morrow DA, Cannon CP, Jesse RL, Newby LK, Ravkilde J, Storrow AB, et al. National Academy of Clinical B. National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines: clinical characteristics and utilization of biochemical markers in acute coronary syndromes. Clin Chem 2007;53: Myocardial infarction redefined-a consensus document of The Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infarction. Eur Heart J 2000;21: Thygesen K, Alpert JS, Jaffe AS, Simoons ML, Chaitman BR, White HD, et al. Third universal definition of myocardial infarction. J Am Coll Cardiol 2012;60: Hamm CW, Bassand JP, Agewall S, Bax J, Boersma E, Bueno H, et al. ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. Eur Heart J 2011;32: Apple FS, Collinson PO, Biomarkers ITFoCAoC. Analytical characteristics of high-sensitivity cardiac troponin assays. Clin Chem 2012;58: Koerbin G, Tate J, Potter JM, Cavanaugh J, Glasgow N, Hickman PE. Characterisation of a highly sensitive troponin I assay and its application to a cardio-healthy population. Clin Chem Lab Med 2012;50: Clerico A, Fortunato A, Ripoli A, Prontera C, Zucchelli GC, Emdin M. Distribution of plasma cardiac troponin I values in healthy subjects: pathophysiological considerations. Clin Chem Lab Med 2008;46: Kavsak PA, MacRae AR, Yerna MJ, Jaffe AS. Analytic and clinical utility of a next-generation, highly sensitive cardiac troponin I assay for early detection of myocardial injury. Clin Chem 2009;55: Apple FS. High-sensitivity cardiac troponin for screening large populations of healthy people: is there risk? Clin Chem 2011;57: Gary L, Sousan A, James C, Ferruccio C, Uttam G, Paul H, et al. Defining, establishing, and verifying reference intervals in the clinical laboratory; approved guideline-third edition. CLSI C28- A3c 2010;28(30). 11. Keller T, Zeller T, Ojeda F, Tzikas S, Lillpopp L, Sinning C, et al. Serial changes in highly sensitive troponin I assay and early diagnosis of myocardial infarction. JAMA 2011;306: Carey RN, Anderson FP, George H, Hartmann AE, Janzen VK, Kallner A, et al. User verification of performance for precision and trueness; approved guideline-second edition CLSI EP15-A2 2005;25(17). Hs-TnI in Koreans with chest pain Apple FS, Smith SW, Pearce LA, Ler R, Murakami MM. Use of the Centaur TnI-Ultra assay for detection of myocardial infarction and adverse events in patients presenting with symptoms suggestive of acute coronary syndrome. Clin Chem 2008;54: Keller T, Zeller T, Peetz D, Tzikas S, Roth A, Czyz E, et al. Sensitive troponin I assay in early diagnosis of acute myocardial infarction. N Engl J Med 2009;361: Melanson SE, Morrow DA, Jarolim P. Earlier detection of myocardial injury in a preliminary evaluation using a new troponin I assay with improved sensitivity. Am J Clin Pathol 2007;128: Reiter M, Twerenbold R, Reichlin T, Haaf P, Peter F, Meissner J, et al. Early diagnosis of acute myocardial infarction in the elderly using more sensitive cardiac troponin assays. Eur Heart J 2011;32: Keller T, Ojeda F, Zeller T, Wild PS, Tzikas S, Sinning CR, et al. Defining a reference population to determine the 99th percentile of a contemporary sensitive cardiac troponin I assay. Int J Cardiol Sandoval Y, Apple FS. The global need to define normality: the 99th percentile value of cardiac troponin. Clin Chem 2014;60: Thygesen K, Alpert JS, White HD. The Joint ESC/ACCF/AHA/ WHF Task Force for the Redefinition of Myocardial Infarction. Universal definition of myocardial infarction. Circulation 2007;116: Alpert JS, Thygesen K, Antman E, Bassand JP. Myocardial infarction redefined-a consensus document of The Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infarction. J Am Coll Cardiol 2000;36: Apple FS, Jesse RL, Newby LK, Wu AH, Christenson RH, Cannon CP, et al. National Academy of Clinical Biochemistry and IFCC Committee for Standardization of Markers of Cardiac Damage Laboratory Medicine Practice Guidelines: analytical issues for biochemical markers of acute coronary syndromes. Clin Chem 2007;53: Panteghini M, Pagani F, Yeo KT, Apple FS, Christenson RH, Dati F, et al. Evaluation of imprecision for cardiac troponin assays at low-range concentrations. Clin Chem 2004;50: Jung CL, Cho SE, Hong KS. Clinical significance of minor elevation of cardiac troponin I. Korean J Lab Med 2008;28: Mahajan VS, Jarolim P. How to interpret elevated cardiac troponin levels. Circulation 2011;124: Roongsritong C, Warraich I, Bradley C. Common causes of troponin elevations in the absence of acute myocardial infarction: incidence and clinical significance. Chest 2004;125: Mingels AM, Jacobs LH, Kleijnen VW, Laufer EM, Winkens B, Hofstra L, et al. Cardiac troponin T elevations, using highly sensitive assay, in recreational running depend on running distance. Clin Res Cardiol 2010;99: Frankenstein L, Remppis A, Giannitis E, Frankenstein J, Hess G, Zdunek D, et al. Biological variation of high sensitive Troponin T in stable heart failure patients with ischemic or dilated cardiomyopathy. Clin Res Cardiol 2011;100: Prasad A, Lerman A, Rihal CS. Apical ballooning syndrome (Tako-Tsubo or stress cardiomyopathy): a mimic of acute myocardial infarction. Am Heart J 2008;155: Scheitz JF, Mochmann HC, Witzenbichler B, Fiebach JB, Audebert HJ, Nolte CH. Takotsubo cardiomyopathy following ischemic stroke: a cause of troponin elevation. J Neurol 2012;259: Klinkman MS, Stevens D, Gorenflo DW. Episodes of care for chest pain: a preliminary report from MIRNET. Michigan Research Network. J Fam Pract 1994;38: Korosoglou G, Lehrke S, Mueller D, Hosch W, Kauczor HU, Humpert PM, et al. Determinants of troponin release in patients with stable coronary artery disease: insights from CT angiography characteristics of atherosclerotic plaque. Heart 2011;97: