中华急诊医学杂志  2016, Vol. 25 Issue (6): 784-791
床边敏感性肌钙蛋白Ⅰ对急性心肌梗死的早期诊断价值
叶子, 黄应雄, 郑梓煜, 熊艳, 徐嘉, 蔡锐彬, 詹红     
510080 广州,中山大学附属第一医院急诊科
摘要目的 评估床边敏感性肌钙蛋白Ⅰ(point-of-care testing for sensitive cardiac troponin Ⅰ,POCT-cTnI)对早期诊断急性心肌梗死(acute myocardial infarction,AMI)的分析性能。 方法 检测中山大学附属第一医院急诊科收治的127例疑诊AMI的急诊胸痛患者在入院3个不同时间点(入院即刻、入院后3 h和6 h)POCT-cTnI和中心实验室高敏肌钙蛋T(central laboratory testing for high sensitive cardiac troponin T,CLT-hscTnT)水平,由两名临床医师根据90 d内所获得的全部临床资料各自独立地给出胸痛病因的最终诊断,并将患者分为AMI组和非AMI组。应用受试者工作特征曲线(receiver operating characteristic curve,ROC曲线)比较POCT-cTnI和CLT-hscTnT两种检测方法对AMI的诊断性能,采用DeLong检验比较ROC曲线下面积(area under the curve,AUC);并计算使用不同诊断界值时的敏感性、特异性、阴性预测值(negative predictive value,NPV)和阳性预测值(positive predictive value,PPV)。 结果 127例胸痛患者中,有40例(31.5%)最终诊断为AMI。POCT-cTnI和CLT-hscTnT在入院即刻水平诊断AMI的准确性用AUC表示,分别为0.901(95%CI:0.901~0.947)和0.907(95%CI:0.842~0.951),两者差异无统计学意义(Z=0.235,P=0.745)。POCT-cTnI在入院后3 h的AUC增加至0.931,与入院即刻相比(AUC,0.858)差异有统计学意义(Z=-2.038,P=0.042),但较入院后6 h(AUC,0.949)差异无统计学意义(Z=-1.435,P=0.151)。POCT-cTnI使用正常人群参考范围上限的第99百分位数为诊断界值(0.023 ng/mL),入院即刻水平的诊断敏感性为77.5%,特异性为94.2%;入院后3 h诊断特性进一步提高,敏感性为96.4%,特异性为92.0%,NPV为98.6%,PPV为81.8%。而CLT-hscTnT使用第99百分位数为诊断界值(0.014 ng/mL),在入院3 h水平的NPV为100%。 结论 POCT-cTnI可在急诊胸痛患者入院后3 h快速准确地识别或除外AMI,诊断性能与CLT-hscTnT相近。
关键词胸痛     急性心肌梗死     肌钙蛋白     早期诊断     受试者工作曲线     诊断性能     诊断界值    
Point-of-care testing for sensitive cardiac troponin I in early diagnosis of acute myocardial infarction
Ye Zi, Huang Yingxiong, Zheng Ziyu, Xiong Yan, Xu Jia, Cai Ruibin, Zhan Hong     
Department of Emergency,The First Affiliated Hospital of Sun Yat-Sen University,Guangzhou 510080,China
Abstract: Objective To evaluate the diagnostic performance of a point-of-care testing for sensitive cardiac troponin Ⅰ(POCT-cTnI)in early diagnosis of chest pain patients who had a high pretest probability of acute myocardial infarction(AMI). Methods Total of 127 patients with new-onset chest pain at the emergency department were enrolled. Blood samples were drawn for the routine blood test, and determined POCT-cTnI and central laboratory testing for high sensitive cardiac troponin T(CLT-hscTnT) at admission, three and then at six hours after admission. All patients were divided into AMI group and non-AMI group according to the final diagnosis, which was adjudicated independently by two physicians who reviewed all available medical records for the 90-day follow-up period, and they were unaware of the results of the investigational assays of cardiac troponins. The receiver operating characteristic(ROC)curves were constructed to assess and compare the diagnostic performance of AMI of two cardiac troponin assays. The comparison of areas under the ROC curves(AUC)was performed by DeLong test, and the sensitivity, specificity, negative predictive values(NPV)and positive predictive values(PPV)for the target markers were calculated by applying a maker-specific cutoff value. Results The final diagnosis of AMI was made in 40 of 127 patients(31.5%). The diagnostic accuracy of the two assays oBtained at presentation, as quantified by AUC, was no statistically differences(AUC for POCT-cTnI, 0.901, 95%CI,0.901 to 0.947; and for CLT-hscTnT, 0.907, 95%CI, 0.842 to 0.951; Z=0.235,P=0.745). The AUC for POCT-cTnI at 3 hours after admission was significantly higher than that on admission(0.931 vs. 0.858; Z=-2.038,P=0.042), while there was on further improvement at 6 hours after admission(0.931 vs. 0.949; Z=-1.435,P=0.151). With use of POCT-cTnI (cutoff value 0.023 ng/mL, which was the 99th percentile upper reference limit)on adimission, the clinical sensitivity was 77.5%, and the specificity was 94.2%. A single sample of POCT-cTnI at 3 hours after admission improved the diagnostic accuracy, with a sensitivity of 96.4%, a specificity of 92.0%, and a NPV of 98.6%, a PPV of 81.8%. While, with use of CLT-hscTnT(cutoff value 0.014 ng/mL, was the 99th percentile upper reference limit)at 3 hours after admission, the NPV reached to 100%. Conclusions The use of a POCT-cTnI assay in chest pain patients can identify and exclude the AMI rapidly and exactly at three hours after admission, and the diagnostic performance is equivalent to CLT-hscTnT.
Key words: Chest pain     Acute myocardial infarction     Point-of-care testing;Cardiac troponin     Early diagnosis     Receiver operating characteristic curve     Diagnostic performance     Cutoff value    

胸痛是急性心肌梗死(acute myocardial infarction,AMI)最常见的的临床症状。如何在胸痛患者早期准确地诊断和除外AMI,一直以来是对急诊医务工作者提出的重大挑战[1]。2007年美国临床生化学会推荐肌钙蛋白(cardiac troponin ,cTn)作为诊断心肌梗死的首选指标[2],并建议实验室心脏标志物周转时间(turnaround time,TAT)应该至少控制在60 min内,最理想为30 min或更短[3],因此床边检测(point-of-care testing ,POCT)作为一种放置随意、即时报告的新型检验方法在急诊科应用越来越广泛[4]。本研究旨在通过检测和比较急诊科疑诊AMI胸痛患者床边敏感性肌钙蛋白I(point-of-care testing for sensitive cardiac troponin I,POCT-cTnI)和中心实验室高敏肌钙蛋T(central laboratory testing for high sensitive cardiac troponin T,CLT-hscTnT),评估POCT-cTnI早期诊断AMI的分析性能。

1 资料与方法 1.1 一般资料

选取中山大学附属第一医院急诊科2011年12月1日至2012年4月1日怀疑AMI的胸痛患者127例。⑴入选标准:胸痛或不适超过5 min;年龄≥18岁;提示AMI可能,临床医生计划进行心肌损伤标志物检测的患者。⑵排除标准:胸痛起病时间超过12 h;肾功能不全;明确或高度疑诊其他非冠脉源性胸痛;外院已经明确诊断为AMI;恶性肿瘤终末期;不能听从医嘱配合诊治的患者。

本项研究通过了中山大学附属第一医院医学伦理委员会审批,所有研究对象均签署知情同意书。

1.2 研究方法 1.2.1 试验设计

本研究为前瞻性的观察性研究。

1.2.2 临床评估

采集患者病史、体格检查、心电图(electrocardiogram,ECG)和中心实验室心肌损伤标志物(包括cTn、磷酸肌酸同工酶和肌红蛋白)等实验室检验结果,以及基线资料如:性别、年龄、危险因素,最严重胸痛起病时间等。

1.2.3 最终诊断的判定标准

每位患者从首次进入急诊科开始至随访90 d内所获得的全部临床资料均由两名临床医师独立审阅,再给出最终诊断,诊断分为:AMI、不稳定型心绞痛[5, 6](unstable angina,UA)、非冠脉性心源性胸痛(如心肌炎、心动过速等)、非心源性胸痛(如未累及冠脉的主动脉夹层、肺栓塞等),以及不明原因的胸痛。如果最终诊断未达成一致,则由第三名医师做出判定。其中AMI的诊断标准参照2012年第3版心肌梗死全球统一定义指南[7]:检测到心肌损伤标志物存在进行性的上升或下降;同时伴有急性心肌缺血的证据。

1.2.4 参与研究的cTn检测方法

采集患者入院即刻、入院后3 h、入院后6 h血标本,同时进行POCT-cTnI和CLT-hscTnT的检测,由研究员单独记录检测结果,不指导并影响临床决策。当患者明确诊断为AMI并需要转诊至导管室或相应专科时,则终止cTn的连续样本采集。⑴ POCT-cTnI:使用AQT90 FLEX cTnI测试卡,及AQT90 FLEX 快速免疫分析仪检测分析;由丹麦雷度米特公司 (Radiometer)生产。第99百分位值为0.023 ng/mL,变异系数(coefficient of variation,CV)≤10%时的最低检测浓度为0.039 ng/mL,可检测范围是0.010~25 ng/mL。 ⑵ CLT-hscTnT:使用Roche cTnT hs检测试剂盒,及Roche cobas e 601全自动免疫分析仪检测分析;由瑞士罗氏诊断公司(Roche Diagnostics)生产。第99百分位值为0.014 ng/mL,CV ≤10%时的最低检测浓度为0.013 ng/mL,可检测范围是0.003~10 ng/mL。上述两种检测方法的检测性能均来自制造商的说明。

1.2.5 随访

通过电话随诊患者本人或家属,完善患者90 d内可获得的全部临床资料。

1.3 统计学方法

使用R 2.11.1统计软件分析。连续性计量资料采用均数±标准差 (x ±s)或中位数(四分位数间距)[M(P25,P75)]表示,对于服从正态分布资料组间比较采用独立样本t检验,不服从正态分布采用wilcox秩和检验;计数资料采用数字和百分数表示,组间比较采用χ2检验或Fisher确切概率法。参与研究的cTn诊断性能由ROC曲线来评价,采用DeLong检验比较ROC曲线下面积(areas under ROC curve,AUC),并计算不同诊断界值时的敏感性、特异性、阴性预测值(negative predictive value,NPV),和阳性预测值(positive predictive value,PPV)。取双侧检验,以P<0.05为差异有统计学意义。

2 结果 2.1 患者的临床基线资料

本研究共纳入符合条件的疑诊AMI胸痛患者127例,其中男性57例(44.4%),年龄(68±11)岁。最终诊断为AMI 40例(31.5%),其中ST段抬高型心肌梗死(ST-segment elevation myocardial infarction,STEMI)18例(14.2%);UA 31例(24.4%),非冠脉心源性胸痛12例(9.5%),非心源性胸痛9例(7.1%),不明原因性胸痛35例(27.5%)。将AMI组和非AMI组患者的临床基线资料进行比较,其中性别构成、吸烟史、既往心肌梗死、既往充血性心力衰竭、就诊时收缩压、就诊首次ECG表现呈ST段抬高、非特异性ST段变化,和ECG有动态变化,差异均有统计学意义,见表 1

表 1 患者临床基线资料 Table 1 Patient demographics and characteristics
临床特点全部患者(n=127)AMI组(n=40)非AMI组(n=87) 统计值P
年龄 (岁,x ±s)68±1169±967±11 t=1.1800.240
男性 (例,%)57 (44.4)27 (67.5)30 (34.5)χ2=12.075<0.01
体质量指数 (岁,x ±s)23.1±3.323.4±2.723.0±3.5 t=0.6210.536
传统危险因素 (例,%)
高血压82 (64.6)25 (62.5)57 (65.5)χ2=0.1090.741
糖尿病30 (23.6)10 (25.0)20 (23.0)χ2=0.0610.804
血脂障碍50 (39.4)13 (32.5)37 (42.5)χ2=1.1550.283
冠心病家族史19 (15.0)6 (15.0)13 (14.9) χ2=0.0000.993
高血压病家族史44 (34.6)10 (25.0)34 (39.1)χ2=2.3990.121
目前吸烟23 (18.1)12 (30.0)11 (12.6)χ2=5.5660.018
既往吸烟(戒>5年)19 (15.0)11 (27.5)8 (9.2)χ2=7.2160.007
既往病史 (例,%)
冠心病56 (44.1)22 (55.0)34 (39.1)χ2=2.8170.093
心肌梗死22 (17.3)11 (27.5)11 (12.6)χ2=4.2230.040
血运重建26 (20.5)10 (25.0)16 (18.4)χ2=0.7350.391
脑卒中15 (11.8)5 (12.5)10 (11.5)χ2=0.0270.870
周围动脉疾病13 (10.2)5 (12.5)8 (9.2)χ2=0.3260.568
心律失常29 (22.8)7 (17.5)22 (25.3)χ2=0.9430.331
充血性心力衰竭10 (7.9)7 (17.5)3 (3.4)χ2=7.4590.006
最严重胸痛起病时间
[h,M(P25,P75)]3(1.75,5)3(1.8,5.7)3(1.5,4.0) w=1684.50.774
临床表现(入急诊时)
收缩压 (mmHg,x ±s)148±31137±29153±31t=-2.7690.006
舒张压 (mmHg,x ±s)79±1477±1480±14t=-1.0780.283
心率 (次/min,x ±s)82±1684±1881±15t=1.0560.293
首份ECG表现 (例,%)
ST段抬高24 (18.9)18 (45.0)6 (6.9)χ2=25.958<0.001
ST段压低42 (33.1)14 (35.0)28 (32.2)χ2=0.0980.754
T波倒置18 (14.2)3 (7.5)15 (17.2)χ2=2.1380.144
病理性Q波6 (4.7)2 (5.0)4 (4.6) Fisher1.000
左/右束支传导阻滞10 (7.9)1 (2.5)9 (10.3) Fisher0.267
非特异性ST段改变12 (9.4)1 (2.5)11 (12.6) Fisher0.005
正常ECG15 (11.8)1 (2.5)14 (16.1) Fisher0.335
ECG动态变化 (例,%)48 (37.8)32 (80.0)16 (18.4)χ2=44.239<0.01
 注:1 mmHg=0.133 kPa
2.2 POCT-cTnI和CLT-hscTnT入院即刻水平对AMI的诊断性能比较

根据最终诊断进行分类,两种检测方法入院即刻cTn水平在AMI组均显著高于其他胸痛病因诊断组,见图 1

胸痛患者入院即刻的两种cTn水平表示为相应检测方法的第99百分位值的倍数,并根据最终诊断进行分类。箱式图的箱子两端分别对应四分位数,中横线为中位数,茎的两端分别对应最大值和最小值,未显示的箱子末端部分表明超过10倍的第99百分值 图 1 不同最终诊断的两种检测方法入院即刻的cTn水平比较 Fig. 1 Levels of cTns at presentation as assessed by two assays,according to the final diagnosis

两种检测方法入院即刻cTn水平对AMI诊断准确性,见图 2:⑴ 对于全部患者(胸痛起病不超过12 h,n=127),入院即刻POCT-cTnI的AUC为0.901(95%CI:0.839~0.963),与之相应CLT-hscTnT的AUC为0.907(95%CI:0.850~0.964),两者差异无统计学意义(Z=0.235,P=0.745)(图 2A)。⑵对于胸痛起病不超过3 h的患者(n=75),入院即刻POCT-cTnI的AUC为0.838(95%CI:0.736~0.940),与之相应CLT-hscTnT的AUC为0.874(95%CI:0.777~0.939),两者差异无统计学意义(Z=1.187,P=0.235)(图 2B)。⑶对于胸痛起病不超过6 h的患者(n=107),入院即刻POCT-cTnI的AUC为0.894(95%CI:0.824~0.963),CLT-hscTnT的AUC为0.900(95%CI:0.835~0.965),两者差异无统计学意义(Z=0.294,P=0.769)(图 2C)。

A. 胸痛起病≤12 h;B. 胸痛起病≤3 h;C. 胸痛起病≤6 h 图 2 两种检测方法入院即刻cTn水平在不同胸痛起病时间患者对AMI诊断的ROC曲线 Fig. 2 Diagnostic accuracy of two cTn assays at presentation shown by ROC curves,according to time since onset of chest pain

根据患者胸痛起病时间的不同进行分类,两种检测方法入院即刻cTn水平应用不同诊断界值对AMI的诊断特性,见表 2

表 2 两种检测方法入院即刻cTn水平应用不同界值对AMI的诊断特性 Table 2 Discriminatory value of two assays for the diagnosis of AMI at presentation
入院即刻cTn诊断特性 POCT-cTnI CLT-hscTnT
99th百分位值 (0.023 ng/mL) 10%CV值 (0.039 ng/mL) 99th百分位值a (0.014 ng/mL)传统诊断界值b (0.1 ng/mL)
百分位数(95%CI)
全部患者
敏感性77.5 (61.1~88.6)65.0 (48.3~78.9)92.5 (78.5~98.0)27.5 (23.7~40.4)
特异性94.2 (86.5~97.9)94.2 (86.5~97.7)77.0 (66.5~85.0)97.7 (91.2~99.6)
NPV90.1 (81.6~95.1)85.4 (76.4~91.5)95.7 (87.1~98.9)74.5 (65.4~82.0)
PPV86.1 (69.7~94.8)83.9 (66.5~93.9)64.9 (51.1~76.8)84.6 (53.6~97.2)
胸痛起病≤3 h
敏感性69.6 (47.0~85.9)52.2 (31.1~72.6)87.0 (65.3~96.6) 13.0 (3.4~34.7)
特异性92.3 (80.6~97.5)92.3 (80.6~97.5)75.0 (60.8~85.5)98.1 (88.4~99.9)
NPV87.3 (74.9~94.3)81.4 (68.7~89.9)92.9 (79.4~98.1)71.8 (59.7~81.6)
PPV80.0 (55.7~93.4)75.0 (47.4~91.7)60.6 (42.2~76.6)75.0 (21.9~98.7)
胸痛起病≤6 h
敏感性74.3 (56.4~86.9)60.0 (42.2~75.6)91.4 (75.8~97.8)25.7 (13.1~43.6)
特异性94.4 (85.7~98.2)94.4 (85.7~98.2)75.0 (63.2~84.1)98.6 (91.5~99.9)
NPV88.3 (78.5~94.2)82.9 (72.7~90.0)94.7 (84.5~98.6)73.2 (63.1~81.4)
PPV86.7 (68.4~95.6)84.0 (63.1~94.7)64.0 (49.1~76.7)90.0 (54.1~99.5)
 注:a hscTnT的10%CV值为0.013 ng/mL,低于该检测方法的第99百分位值,故只展示第99百分位值;b传统诊断界值:根据1970年WHO对AMI的定义标准,cTnT的判断值为0.1 ng/mL (由前代Elecsys troponinT检测法ROC曲线分析结果所决定)[21]
2.3 POCT-cTnI和CLT-hscTnT入院后不同时间点的单次样本水平对AMI的诊断性能比较

入院即刻、入院后3 h、入院后6 h cTn水平对AMI诊断准确性,见图 3。POCT-cTnI(n=82)在入院即刻的AUC为0.858(95%CI:0.764~0.952),入院后3 h的AUC为0.931(95%CI:0.866~0.996),入院后6 h的AUC为0.949(95%CI:0.885~0.985)(图 3A);其中入院即刻与入院后3 h相比,两者差异有统计学意义(Z=-2.038,P=0.042),入院即刻与入院后6 h相比,两者差异 有统计学意义(Z=-2.216,P=0.027),入院后3 h与入院后6 h相比,两者差异无统计学意义(Z=-1.435,P=0.151)。 CLT-hscTnT(n=79)在入院即刻的AUC为0.885(95%CI:0.802~0.967),入院后3 h的AUC为0.934(95%CI:0.879~0.988),入院后6 h的AUC为0.965(95%CI:0.935~0.999)(图 3B),其中入院即刻与入院后 3 h相比,两者差异无统计学意义(Z=-1.785,P=0.074),入院即刻与入院后6 h相比,两者差异具有统计学意义(Z=-2.420,P=0.016),入院后3 h与入院后6 h相比,两者差异有统计学意义(Z=-2.378,P=0.017)。

A. POCT-cTnI不同时间点对AMI诊断的ROC曲线;B. CLT-hscTnT不同时间点对AMI诊断的ROC曲线 图 3 两种检测方法入院后不同时间点cTn对平对AMI诊断的ROC曲线 Fig. 3 ROC curves for baseline and serial samples of two cTn assays respectively

两种检测方法入院后3 h、入院后6 hcTn水平应用不同诊断界值所对AMI的诊断特性,见表 3

表 3 两种检测方法入院后连续检测cTn水平应用不同界值对AMI的诊断特性 Table 3 Discriminatory value of two assays for the diagnosis of AMI at serial sampling
入院即刻cTn诊断特性 POCT-cTnI CLT-hscTnT
99th百分位值 (0.023 ng/mL) 10%CV值 (0.039 ng/mL) 99th百分位值a (0.014 ng/mL)传统诊断界值b (0.1 ng/mL)
百分位数(95%CI)
入院3 h
敏感性96.4 (79.8~99.8)82.1 (62.4~93.2)100 (85.0~100)60.7 (40.7~77.9)
特异性92.0 (82.8~96.7)93.3 (84.5~97.5)77.2 (66.1~85.6)97.5 (90.3~99.6)
NPV98.6 (91.2~99.9)93.3 (84.5~97.5)100 (92.6~100)87.5 (78.3~93.3)
PPV81.8 (63.9~92.4)82.1 (62.4~93.2)60.9 (45.4~74.5)89.5 (65.5~98.2)
入院6 h
敏感性96.4 (79.8~99.8)75.0 (54.8~88.6)100 (88.0~100)86.1 (69.7~94.8)
特异性90.0 (78.8~95.9)98.3 (89.9~99.9)64.3 (50.3~76.3)92.9 (81.9~97.7)
NPV98.2 (89.0~99.9)89.4 (78.8~95.3)100 (88.0~100)91.2 (80.0~96.7)
PPV81.8 (63.9~92.4)95.5 (75.1~99.8)64.3 (50.3~76.3)88.6 (72.3~96.3)
 注:a hscTnT的10%CV值为0.013 ng/mL,低于该检测方法的第99百分位值,故只展示第99百分位值;b传统诊断界值:根据1970年WHO对AMI的定义标准,cTnT的判断值为0.1 ng/mL (由前代Elecsys troponinT检测法ROC曲线分析结果所决定)[21]
3 讨论

心肌损伤标志物的联合检测常被提倡用于AMI的早期诊断[8, 9, 10],因为在心肌坏死的早期,传统cTn敏感性较低而难以在循环中被检测出来。但随着新一代敏感性cTn的应用[11],cTn在正常人群参考范围内以及心肌坏死的早期就能被检测到[12]。数项研究表明,单独使用中心实验室敏感性cTn,并将AMI诊断界值设定在正常人群参考上限的第99百分位数[13],或是10%CV时的最小浓度值[14],均具有良好的早期诊断性能。2011欧洲心脏病学会非ST段抬高型急性冠脉综合征指南已明确提出,应用hscTn可实现“3 h快速排除诊断方案”[15]

近年来,研究表明POCT-cTn可以显著的缩短TAT[16],能在第一时间辅助临床医师作出决策,因此在急诊科的应用越来越广泛,但其诊断性能在各项研究中的评价不尽相同。2004年Collinson等[17]的研究认为POCT和CLT(均检测cTnT,Roche Diagnostics)在诊断准确性上是相近的;以及在RATPAC研究[18]中对进入到POCT组的全部亚组人群进行回顾性分析,认为POCT-cTnI(Siemens Healthcare Diagnostics)不需要联合其他心肌损伤标志物就可在90 min内实现对胸痛患者的AMI诊断评估。但较之CLT-cTn,即使是可定量检测的POCT-cTn,大部分的研究仍认为其对AMI的诊断性能,特别是敏感性偏低[19, 20]。因此,本研究对中山大学附属第一医院急诊科127例胸痛患者进行前瞻性的观察性研究,较为系统全面地评估了POCT-cTnI使用指南推荐的诊断界值时[7]早期诊断或除外AMI的分析性能。

本研究主要有四点发现。第一,入院即刻的POCT-cTnI水平就具有很高的诊断准确性,AUC面积可达0.901,而CLT-hscTnT的AUC为0.907,两者诊断准确性相近。第二,无论是以在正常人群第99百分位值或10%CV时的最小浓度作为诊断界值,入院即刻的POCT-cTnI水平均具备良好的诊断特性。其中,POCT-cTnI在第99百分位数时的敏感性为77.5% ,特异性为94.2%,NPV为90.1%,PPV为86.1%;CLT-hscTnT在相应诊断界值时(0.014 ng/mL)同样显示出良好的诊断特性,敏感性为92.5%,特异性为77.0%。第三,入院后3 h POCT-cTnI的ROC曲线分析显示,AUC增加至0.931,诊断准确性较入院即刻水平进一步增加,并且与入院后6 h(AUC=0.949)的诊断准确性相近;而在诊断特性上,入院后3 h POCT-cTnI在第99百分位值的敏感性为96.4%,特异性为92.0%,NPV为98.6%,PPV为81.8%,表现出优异的除外诊断能力。此外笔者还可以看到,CLT-hscTnT应用第99百分位值有着更加“令人放心”的除外诊断价值,3 h NPV达100%,这也与Keller[5]和Reichlin等[6]关于CLT-hscTn的两项多中心研究结果相一致。第四,即使对于胸痛起病距就诊时间较短的患者,POCT-cTnI也能表现出较好的诊断准确性,在胸痛起病不超过3 h 和6 h的患者中,POCT-cTnI的AUC分别达到0.838和0.894。

以第99百分位数作为诊断界值,POCT-cTnI表现出与CLT-hscTnT同样良好的早期诊断性能,这为POCT-cTnI在入院后3 h的检测结果可实现诊断或除外AMI提供了临床实践依据,从而使早期诊断为AMI的这部分患者有可能通过更早地开始证据性用药,更早地接受血运重建,以及更早地收入心血管科接受专科治疗,以降低不良心血管事件的发生。同时对于早期除外AMI的胸痛患者,使之有可能判定为低危而减少不必要的急诊滞留,加快诊疗的周转,节约医疗资源;或者更为及时地提醒医生可能需要结合D-二聚体或胸部CT等检查手段,以鉴别是否存在其他高危胸痛如主动脉夹层、肺栓塞等情况。

值得一提的是,CLT-hscTnT如果应用0.1 ng/mL这一传统临床诊断界值[21]时,入院即刻水平的诊断特异性虽然很高(97.7%),但是敏感性仅为27.5%;3 h敏感性也只有60.7%,6 h敏感性可达86.1%,因此提示医院如仍沿用传统诊断界值作为诊断标准时,对于首次cTn阴性的患者,临床医师往往需要将cTn的复查时间延长至入院后6~9 h以防止出现漏诊。这也正如在关于hscTn中国专家共识中所提到[22]的“hscTn的诊断起点一定要降到第99百分位值,否则‘高敏’就毫无意义”。

本研究显示出POCT-cTnI对AMI有较高的早期诊断价值,但临床应用中仍要注重全面的临床评估,包括详细的采集病史、体格检查、动态监测ECG,以及根据患者病情需要完善超声心动图[23]、64排螺旋CT血管成像[24]等检查,以鉴别AMI与其他可能引起cTn升高的疾病,如心肌炎、心肌病、主动脉夹层、心力衰竭、肾功能不全等[7];同时对STEMI患者来说,ECG仍然是必不可少的诊断工具,当cTn结合临床评估和ECG时,应该可以表现出更高的诊断准确性[25],从而进一步减少临床诊断不确定的比例。研究局限性:第一,测定cTn的POCT方法众多[26, 27],特别是cTnI,因此本研究结论推广到其他床边敏感性cTn的临床应用时还需谨慎。第二,本研究只关注了在规定时间点上单次样本的cTn诊断特性,而对监测cTn动态变化相关的诊断性能尚未评估。此外,本研究为观察性研究,并未将POCT-cTnI的早期诊断价值真正的应用于临床实践进行量化评估,因此还有待前瞻性的干预性试验进一步验证。

参考文献
[1] 江慧琳, 陈晓辉. 重视急性胸痛的危险分层,优化急性胸痛管理流程[J]. 中华急诊医学杂志,2015,24(7):700-703. DOI:10.3760/cma.j.issn.1671-0282.2015.07.002. Jiang HL, Chen XH.Pay attention to the risk stratification of acute chest pain and optimize the management of acute chest pain process [J]. Chin J Emerg Med, 2015, 24 (7) : 700-703.
[2] Morrow D A, Cannon C P, Jesse R L, et al. National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines: clinical characteristics and utilization of biochemical markers in acute coronary syndromes[J]. Clin Chem,2007,53(4):552-574. DOI:10.1373/clinchem.2006.084194.
[3] Nichols J H, Christenson R H, Clarke W, et al. Executive summary. The National Academy of Clinical Biochemistry Laboratory Medicine Practice Guideline: evidence-based practice for point-of-care testing[J]. Clin Chim Acta,2007,379(1/2):14-28, 29-30. DOI: 10.1016/j.cca.2006.12.025.
[4] 黄欢, 陈怡, 朱长清. 床边检验在急诊室的应用价值与现状[J]. 中华急诊医学杂志,2011,20(10):1116-1117. DOI: 10.3760/cma.j.issn.1671-0282.2011.10.030. Huang H, Chen Y, Zhu CQ. Application value and current situation of the bedside testing in the emergency department [J]. Chin J Emerg Med, 2011, 20 (10) : 1116-1117.
[5] Keller T, Zeller T, Peetz D, et al. Sensitive troponin I assay in early diagnosis of acute myocardial infarction[J]. N Engl J Med,2009,361(9):868-877. DOI: 10.1056/NEJMoa0903515.
[6] Reichlin T, Hochholzer W, Bassetti S, et al. Early diagnosis of myocardial infarction with sensitive cardiac troponin assays[J]. N Engl J Med,2009,361(9):858-867. DOI: 10.1056/NEJMoa0900428.
[7] Thygesen K, Alpert J S, Jaffe AS, et al. Third universal definition of myocardial infarction[J]. Circulation,2012,126(16):2020-2035. DOI: 10.1161/CIR.0b013e31826e1058
[8] Ng SM, Krishnaswamy P, Morissey R, et al. Ninety-minute accelerated critical pathway for chest pain evaluation[J]. Am J Cardiol,2001,88(6):611-617. DOI: 10.1016/S0002-9149(01)01801-X.
[9] Than M, Cullen L, Reid CM, et al. A 2-h diagnostic protocol to assess patients with chest pain symptoms in the Asia-Pacific region (ASPECT): a prospective observational validation study[J]. Lancet,2011,377(9771):1077-1084. DOI: 10.1016/S0140-6736(11)60310-3.
[10] 冯丹, 曹华军. 心肌标志物联合检测在急性心肌梗死早期诊断中的应用[J]. 中国急救医学,2014(9):840-842. DOI: 10.3969/j.issn.1002-1949.2014.09.018. Dan, FENG, Hua-jun, CAO. Combined detection of myocardial markers in the early diagnosis of acute myocardial infarction. [J]. Chin J Critical Care Med,2014(9):840-842.
[11] Apple FS. A new season for cardiac troponin assays: it's time to keep a scorecard[J]. Clin Chem,2009,55(7):1303-1306. DOI: 10.1373/clinchem.2009.128363.
[12] Collinson PO, Clifford-Mobley O, Gaze D, et al. Assay imprecision and 99th-percentile reference value of a high-sensitivity cardiac troponin I assay[J]. Clin Chem,2009,55(7):1433-1434. DOI: 10.1373/clinchem.2009.124925.
[13] Scharnhorst V, Krasznai K, Van'TVM, et al. Rapid detection of myocardial infarction with a sensitive troponin test[J]. Am J Clin Pathol,2011,135(3):424-428. DOI: 10.1309/AJCPA4G8AQOYEKLD.
[14] Eggers KM, Oldgren J, Nordenskjold A, et al. Diagnostic value of serial measurement of cardiac markers in patients with chest pain: limited value of adding myoglobin to troponin I for exclusion of myocardial infarction[M]. 2004.574-581. DOI: 10.1016/j.ahj.2004.04.030.
[15] Hamm CW, Bassand J P, Agewall S, et al. ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation: The Task Force for the management of acute coronary syndromes (ACS) in patients presenting without persistent ST-segment elevation of the European Society of Cardiology (ESC)[J]. Eur Heart J,2011,32(23):2999-3054. DOI: 10.1093/eurheartj/ehr236.
[16] Kendall J, Reeves B, Clancy M. Point of care testing: randomised controlled trial of clinical outcome[J]. BMJ,1998,316(7137):1052-1057. DOI: org/10.1136/bmj.316.7137.1052.
[17] Collinson PO, John C, Lynch S, et al. A prospective randomized controlled trial of point-of-care testing on the coronary care unit[J]. Ann Clin Biochem,2004,41(Pt 5):397-404. DOI: 10.1258/0004563041731547.
[18] Collinson P, Goodacre S, Gaze D, et al. Very early diagnosis of chest pain by point-of-care testing: comparison of the diagnostic efficiency of a panel of cardiac biomarkers compared with troponin measurement alone in the RATPAC trial[J]. Heart,2012,98(4):312-318. DOI: 10.1136/heartjnl-2011-300723.
[19] Bock JL, Singer AJ, Thode HJ. Comparison of emergency department patient classification by point-of-care and central laboratory methods for cardiac troponin I[J]. Am J Clin Pathol,2008,130(1):132-135. DOI: 10.1309/NVXH8DL5HWFDNB74.
[20] Venge P, Ohberg C, Flodin M, et al. Early and late outcome prediction of death in the emergency room setting by point-of-care and laboratory assays of cardiac troponin I[J]. Am Heart J,2010,160(5):835-841. DOI: 10.1016/j.ahj.2010.07.036.
[21] Muller-Bardorff M, Hallermayer K, Schroder A, et al. Improved troponin T ELISA specific for cardiac troponin T isoform: assay development and analytical and clinical validation[J]. Clin Chem,1997,43(3):458-466.
[22] 中华医学会心血管病学分会, 中华心血管病杂志编辑委员会. 高敏心肌肌钙蛋白在急性冠状动脉综合征中的应用中国专家共识[J]. 中华检验医学杂志,2012,35(12):1073-1076. DOI: 10.3760/cma.j.issn.1009-9158.2012.12.004. Cardiovascular Epidemiology Branch of Chinese Medical Association, Cardiovascular Disease Editor Committee. Application of high sensitive myocardial troponin in acute coronary syndrome China expert consensus [J]. Chin J Lab Med,2012,35(12):1073-1076.
[23] 吴英, 林中园, 干青晖. 心电图、心肌标志物与超声心动图临床应用研究[J]. 中华急诊医学杂志,2014,23(10):1162-1165. DOI: 10.3760/cma.j.issn.1671-0282.2014.10.023. Wu Y, Lin ZY, Gan QH. Clinical application research of ectrocardiogram (ecg), myocardial marker and echocardiography [J]. Chin J Emerg Med, 2014,23(10):1162-1165.
[24] Johnson T R, Nikolaou K, Wintersperger B J, et al. ECG-gated 64-MDCT angiography in the differential diagnosis of acute chest pain[J]. AJR Am J Roentgenol,2007,188(1):76-82. DOI: 10.2214/AJR.05.1153.
[25] 陶新, 张超, 高洁. 急诊心电图ST段抬高病因分析及与急性心肌梗死的鉴别方法[J]. 中国急救复苏与灾害医学杂志,2014(7):598-601. DOI: 10.3969/j.issn.1673-6966.2014.07.006. Tao X, Zhang C, Gao J. Clinical analysis of emergency ECG ST segment elevation and identification method of acute myocardial infarction.[J]. Chin J Emerg Res Disa Med, 2014(7):598-601.
[26] Bingisser R, Cairns C, Christ M, et al. Cardiac troponin: a critical review of the case for point-of-care testing in the ED[J]. Am J Emerg Med,2012,30(8):1639-1649. DOI: 10.1016/j.ajem.2012.03.004.
[27] 周发展, 武君, 张春玲, 等. 替罗非班应用于急诊经皮冠状动脉介入治疗对急性心肌梗死患者心肌灌注和内皮功能的影响[J/CD]. 中华危重症医学杂志:电子版, 2016, 9(1):3-8. DOI: 10.3877/cma.j.issn.1674-6880.2016.01.001.Zhou FZ, Wu J, Zhang CL, et al. Effect of intracoronary tirofiban on myocardial reperfusion and endothelial function in patients with acute myocardial infarction undergoing percutaneous coronary intervention [J/CD]. Chin J Crit Care Med, 2016, 9 (1): 3-8.