Reference value for cardiac troponin I in a multi-ethnic group

High-sensitivity cardiac troponin I: is ethnicity relevant?

AIMS

To evaluate 99th percentile upper reference limits (URLs) and investigate ethnic differences for the Abbott Architect high-sensitivity cardiac troponin I (hs-cTnI) in a middle-aged to elderly cosmopolitan population.

METHODS

In subjects without cardiovascular disease and after outlier exclusion, data on hs-cTnI from 149 white men, 150 white women, 150 South Asian (SA) men and 150 SA women in their sixth, seventh and eight decades were analysed. Each ethnicity-gender-decade subgroup consisted of 50 patients except white men in their sixth decade (n=49).

RESULTS

The overall, women and men hs-cTnI 99th percentile URLs were 22.1, 17.9 and 24.8 ng/L, respectively. Median (IQR) hs-cTnI was higher in men (2.7 (1.8-4.1) ng/L) than in women (1.9 (1.1-3.2) ng/L; p<0.001). White men (3.2 (2.2-4.4) ng/L) had higher hs-cTnI than SA men (2.5 (1.6-3.6) ng/L; p<0.001), white women (2.1 (1.3-3.3) ng/L; p<0.001) and SA women (1.6 (1.0-3.0) ng/L; p<0.001). Hs-cTnI in white women was similar to SA women (p=0.07) and SA men (p=0.07). Patients in the eighth decade had higher hs-cTnI (p<0.05) than those in sixth decade within each ethnicity-gender subgroup. Of significant associations, age had the greatest impact on hs-cTnI followed by gender and then ethnicity.

CONCLUSION

We report white-SA differences in hs-cTnI in men and a similar trend in women. We confirm age and gender differences in hs-cTnI, irrespective of ethnicity. Further studies are required to determine whether ethnicity-specific age and gender 99th percentile URLs improve detection or exclusion of myocardial injury.

The ethnicity-specific association of biomarkers with the angiographic severity of coronary artery disease

Background

Risk factor burden and clinical characteristics of patients with coronary artery disease (CAD) differ among ethnic groups. We related biomarkers to CAD severity in Caucasians, Chinese, Indians and Malays.

Methods

In the Dutch-Singaporean UNICORN coronary angiography cohort (n = 2033) we compared levels of five cardiovascular biomarkers: N-terminal pro-brain natriuretic peptide (NTproBNP), high-sensitivity C-reactive protein (hsCRP), cystatin C (CysC), myeloperoxidase (MPO) and high-sensitivity troponin I (hsTnI). We assessed ethnicity-specific associations of biomarkers with CAD severity, quantified by the SYNTAX score.

Results

Adjusted for baseline differences, NTproBNP levels were significantly higher in Malays than in Chinese and Caucasians (72.1 vs. 34.4 and 41.1 pmol/l, p < 0.001 and p = 0.005, respectively). MPO levels were higher in Caucasians than in Indians (32.8 vs. 27.2 ng/ml, p = 0.026), hsTnI levels were higher in Malays than in Caucasians and Indians (33.3 vs. 16.4 and 17.8 ng/l, p < 0.001 and p = 0.029) and hsTnI levels were higher in Chinese than in Caucasians (23.3 vs. 16.4, p = 0.031). We found modifying effects of ethnicity on the association of biomarkers with SYNTAX score. NTproBNP associated more strongly with the SYNTAX score in Malays than Caucasians (β 0.132 vs. β 0.020 per 100 pmol/l increase in NTproBNP, p = 0.032). For MPO levels the association was stronger in Malays than Caucasians (β 1.146 vs. β 0.016 per 10 ng/ml increase, p = 0.017). Differing biomarker cut-off levels were found for the ethnic groups.

Conclusion

When corrected for possible confounders we observe ethnicity-specific differences in biomarker levels. Moreover, biomarkers associated differently with CAD severity, suggesting that ethnicity-specific cut-off values should be considered.

The global need to define normality: the 99th percentile value of cardiac troponin

BACKGROUND

How to select a presumably normal population for the establishment of 99th percentile cutoffs for cardiac troponin assays has not been adequately addressed. Lack of attention to this question can result in misleading medical decision cutoffs.

CONTENT

From our review of the peer-reviewed literature, including international recommendations, no uniform procedure is followed and no uniform guideline has been published by experts or regulatory agencies to guide researchers or manufacturers of cardiac troponin assays in their quest to define the health or "normality" of a reference population that is used to establish an accurate 99th percentile value. As we progress globally into the era of high-sensitivity cardiac troponin assays, we propose several suggested approaches to define presumably normal individuals by use of clinical and biomarker surrogates.

SUMMARY

Our uniform approach to defining who is normal and who may not be normal will help to define diagnostic and risk outcomes assessments in the management of patients with suspected myocardial injury, both for use in current clinical practice and clinical research, as well as for the potential future use of cardiac troponin in primary prevention.

A comprehensive review of upper reference limits reported for (high-)sensitivity cardiac troponin assays: the challenges that lie ahead

Cardiac troponins (cTn) are the preferred markers for the diagnosis of acute myocardial infarction (AMI). The guidelines recommend the use of the 99th percentile upper reference concentration of a healthy population as the diagnostic cut-off for AMI. However, a broad range of upper reference limits is still employed, complicating the diagnosis of AMI. This overview is meant to assist laboratory specialists to define an appropriate cut-off value for the diagnosis of AMI. Therefore, we provide an overview of the analytical performance and upper reference limits of seven (high-)sensitivity cTn assays: Roche high-sensitivity cTnT and ADVIA Centaur, Stratus CS, Dimension Vista, Vitros ECi, Access and Architect cTnI assays. It is shown that none of the reference populations completely met the guidelines, including those in package inserts. Forty percent of the studies collected less than the advised minimum of 300 subjects. Many studies (50%) did not report their inclusion criteria, while lower 99th percentile limits were observed when more stringent selection criteria were applied. Higher troponin cut-offs were found in men and elderly subjects, suggesting sex- and age-specific cut-offs would be considered. Therefore, there is still need for a large, rigorously screened reference population to more accurately establish cTn upper reference limits.