The new, highly sensitive cardiac troponin T assay finds detectable levels of the biomarker in 25% of adults in the general population who would not be identified by the standard troponin T assay, and that result often correlates with cardiac structural abnormalities, according to large cohort study reported in the Dec. 8 issue of JAMA.

In addition, elevated cardiac troponin T levels identified with the highly sensitive assay also correlate with all-cause and cardiovascular mortality, independently of other risk factors and even in people thought to be at low cardiovascular risk, said Dr. James A. de Lemos of the University of Texas Southwestern Medical Center, Dallas, and his associates.

The highly sensitive assay detects levels of cardiac troponin T that are approximately one-tenth of the levels detectable with the standard assay. Dr. de Lemos and his colleagues examined the results of this assay in a general population cohort of adults aged 30-65 years participating in the Dallas Heart Study. The 3,546 subjects in this random probability sample had detailed cardiovascular profiles, including MRI and electron-beam CT imaging of the heart and aorta, and their mortality was tracked for a median of 6 years.

The prevalence of detectable cardiac troponin T by this highly sensitive assay was 25% in this multiethnic cohort that included a high proportion of blacks and women. In contrast, the standard assay found detectable levels in only 0.7%.

Higher levels of the biomarker on the highly sensitive assay were associated with cardiac structural abnormalities including left ventricular hypertrophy (both wall thickening and dilation) and left ventricular systolic dysfunction, even in subjects who were asymptomatic, had no known CVD, and were classified as low-risk by their Framingham Risk Scores.

“Moreover, higher cardiac troponin T levels demonstrate[d] a graded association with all-cause and cardiovascular mortality, independent of traditional risk factors, renal function, and levels of other biomarkers” such as high-sensitivity C-reactive protein and N-terminal prohormone brain natriuretic peptide, the investigators said (JAMA 2010;304:2503-12).

“Prior studies have described associations between increased troponin levels detected with standard assays and future risk for mortality. Here, we report that these associations extend to much lower troponin levels not detected with assays in current clinical use,” they added.

More research is needed to determine whether routine use of the highly sensitive assay would aid in cardiovascular risk assessment in the general population.

In the meantime, the findings have important implications for the use of this assay for diagnosing acute MI in the hospital setting. Given that one-fourth of the general population have “elevated” troponin T on this test, false-positive diagnoses will increase. “It is possible that widespread application of highly sensitive assays without integrating new approaches to discriminate acute injury will expose some patients to unnecessary risk and expense,” Dr. de Lemos and his associates noted.

The Dallas Heart Study was supported by the Donald W. Reynolds Foundation and the U.S. National Institutes of Health. Assays were provided by Roche Diagnostics. Dr. de Lemos and his associates reported ties to numerous pharmaceutical and device manufacturers.

Copyright (c) 2010 Elsevier Global Medical News. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

据12月8日发表于《美国医学会杂志》(JAMA)的一项大规模研究报告，普查中采用新型高敏心肌肌钙蛋白T试验可在25%的成人中检出这种生物标志物，而这部分人使用标准肌钙蛋白T试验则无法检出此标志物。

研究者从达拉斯心脏研究中随机选取了3,546例年龄在30~65岁间的普通成人(民族组成多样，其中黑种人和女性比例较高)作为队列研究的受试者，并用这种新方法对受试者的心肌肌钙蛋白T水平进行了检测。所有受试者均有详细的心血管疾病档案，其中包括对受试者心脏和动脉进行的磁共振成像(MRI)和电子束计算机断层扫描(CT)成像及死亡调查资料(随访中位时间为6年)。

新方法对心肌肌钙蛋白T的检出率为25%，而标准方法检出率仅为0.7%，新方法的灵敏度比标准心肌肌钙蛋白T试验高10倍。心肌肌钙蛋白T浓度的增量大小与患者全死因和心血管死亡率风险分级紧密相关，且这种关联独立于传统危险因素(如肾功能和其他生物标志物的浓度)而存在(JAMA 2010;304:2503-12)。

心肌肌钙蛋白T浓度与心脏结构异常(包括左心室肥大、左心室收缩功能不全)甚至无症状性心血管疾病(CVD)均高度相关，Framingham风险评分常将后者错误划分为低风险患者，应用此种新检测方法有望对此类患者进行早期诊断。

既往研究证明，心肌肌钙蛋白T浓度增高与患者未来死亡风险相关，而本研究证明，这一关联在患者心肌肌钙蛋白T浓度更低时同样存在。是否应将这种新型高敏检测方法用于普通人群心血管风险评估尚有待进一步评估。

达拉斯心脏研究由Donald W. Reynolds基金会和美国国立卫生研究院赞助。新型检测方法由罗氏诊断公司提供。作者表示与多家制药公司和医疗器械公司存在关联。

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