Scharnhorst Volkher, Krasznai Krisztina, van 't Veer Marcel, Michels Rolf H
Clinical Laboratory, Catharina Hospital, Eindhoven, the Netherlands.
Clin Chem. 2012 Aug;58(8):1208-14. doi: 10.1373/clinchem.2011.179903. Epub 2012 Jun 8.
New-generation high-sensitivity assays for cardiac troponin have lower detection limits and less imprecision than earlier assays. Reference 99th-percentile cutoff values for these new assays are also lower, leading to higher frequencies of positive test results. When cardiac troponin concentrations are minimally increased, serial testing allows discrimination of myocardial infarction from other causes of increased cardiac troponin. We assessed various measures of short-term variation, including absolute concentration changes, reference change values (RCVs), and indices of individuality (II) for 2 cardiac troponin assays in emergency department (ED) patients.
We collected blood from patients presenting with cardiac chest pain upon arrival in the ED and 2, 6, and 12 h later. Cardiac troponin was measured with the high-sensitivity cardiac troponin T (hs-cTnT) assay (Roche Diagnostics) and a sensitive cTnI assay (Siemens Diagnostics). Cardiac troponin results from 67 patients without acute coronary syndrome or stable angina were used in calculating absolute changes in cardiac troponin, RCVs, and II.
The 95th percentiles for absolute change in cardiac troponin were 8.3 ng/L for hs-cTnT and 28 ng/L for cTnI. Within-individual and total CVs were 11% and 14% for hs-cTnT and 18% and 21% for cTnI, respectively. RCVs were 38% (hs-cTnT) and 57% (cTnI). The corresponding log-normal RCVs were +46%/-32% for hs-cTnT and +76%/-43% for cTnI. II values were 0.31 (cTnI) and 0.12 (hs-cTnT).
The short-term variations and IIs of cardiac troponin were low in ED patients free of ischemic myocardial necrosis. The detection of cardiac troponin variation exceeding reference thresholds can help to identify ED patients with acute myocardial necrosis whereas variation within these limits renders acute coronary syndrome unlikely.
新一代心肌肌钙蛋白高敏检测法比早期检测法具有更低的检测限和更小的不精密度。这些新检测法的第99百分位数参考临界值也更低，导致检测结果阳性的频率更高。当心肌肌钙蛋白浓度轻微升高时，连续检测有助于区分心肌梗死与其他导致心肌肌钙蛋白升高的原因。我们评估了急诊科（ED）患者中两种心肌肌钙蛋白检测法的短期变异的各种指标，包括绝对浓度变化、参考变化值（RCV）和个体指数（II）。
我们在患者抵达急诊科时以及之后2、6和12小时采集有心脏胸痛症状患者的血液。使用高敏心肌肌钙蛋白T（hs-cTnT）检测法（罗氏诊断公司）和一种敏感的肌钙蛋白I检测法（西门子诊断公司）检测心肌肌钙蛋白。来自67例无急性冠状动脉综合征或稳定型心绞痛患者的心肌肌钙蛋白结果用于计算心肌肌钙蛋白的绝对变化、RCV和II。
心肌肌钙蛋白绝对变化的第95百分位数，hs-cTnT为8.3 ng/L，肌钙蛋白I为28 ng/L。hs-cTnT的个体内变异系数和总变异系数分别为11%和14%，肌钙蛋白I分别为18%和21%。RCV分别为38%（hs-cTnT）和57%（肌钙蛋白I）。相应的对数正态RCV，hs-cTnT为+46%/-32%，肌钙蛋白I为+76%/-43%。II值分别为0.31（肌钙蛋白I）和0.12（hs-cTnT）。
在无缺血性心肌坏死的急诊科患者中，心肌肌钙蛋白的短期变异和II较低。检测到心肌肌钙蛋白变异超过参考阈值有助于识别患有急性心肌坏死的急诊科患者，而在这些限度内的变异则不太可能是急性冠状动脉综合征。
