A Study of Population and Sex-specific Troponin Cutoffs for Ruling Out Acute Myocardial Infarction

The present use of non-sex specific diagnostic cut-off levels of troponins in the diagnosis of acute myocardial infarction (MI) leads to under-diagnostication of acute MI in women and over-diagnostication in men. The purpose of this study is to document this through a randomized nationwide clinical implementation of population and sex-specific cut-off levels.

Coronary artery disease (CAD) is globally the leading cause of mortality for men and women. The latest consensus statement defines myocardial infarction as 1) a rise and/or fall in cardiac troponins with 2) at least one value above the 99th percentile upper reference limit (URL) in the context of 3) symptoms or clinical evidence of myocardial ischemia. Thus, levels of cardiac troponins play a key role in the diagnostic work-up in general. Currently, uniform manufacturer-provided URLs, defined by the 99th percentile of cardiac troponins in a healthy reference population, is applied in Danish hospitals as a diagnostic cut-off for acute MI for both men and women.

Lower levels of cardiac troponins are seen in healthy women as compared to healthy men, i.e. twice as high levels are seen in men. On this basis the clinical use of one uniform 99th percentile URL for cardiac troponins - i.e. applying the same diagnostic levels for men and women - may lead to a systematic under-diagnostication of acute MI in women and potentially an over-diagnostication of acute MI in men. Accordingly, the use of sex-specific 99th percentile URL of cardiac troponins are now recommended in recent guidelines by international cardiological societies, but this remains to be introduced in clinical practice.

The 99th percentile URLs for cardiac troponins currently used in Danish Hospitals are provided by the manufacturer of each specific assay based on blood samples from a healthy reference population collected by the manufacturer. Studies have shown that the 99th percentile value is dependent on patient sex as well as on the reference population selected and the definition for "healthy" used in these studies. It is well known that the 99th percentile URL should stem from a local reference population. This recommendation has never been implemented in Denmark.

The overall purpose of the study is to evaluate the clinical effect of implementing population and sex-specific 99th percentile URL for cardiac troponins in Denmark.

To determine the sex-specific 99th percentile URLs of troponins based on a healthy Danish reference population, blood samples from healthy Danish blood donors, were analyzed using one troponin T assay and four troponin I assays. Second, the DANSPOT study is a nationwide cluster-randomized trial with "stepped-wedge" design with participation of all 22 Danish hospital laboratories and associated departments of cardiology. With one-month intervals, each of 22 centers are randomized to shift from the presently applied uniform 99th percentile URL of troponin to our newly determined population and sex-specific 99th percentiles URLs. Each patient is followed up for 12 months after their first troponin measurement during the index admission.

The clinical significance of sex-specific 99th percentile URLs for troponin remains poorly investigated and, for the same reason, not yet implemented in Denmark or many other countries. The basic hypothesis of the DANSPOT study is that the implementation of population and sex-specific 99th URLs for troponin, will ensure that the right patients receive the right treatment. The investigators expect to detect significantly more women with acute MI, theoretically resulting in a more accurate diagnosis and treatment of women and men with acute MI. This would be guideline-defining for implementing sex-specific cutoffs for cardiac troponin in Denmark and internationally, as recommended by professional cardiological societies.

Inclusion criteria

for the primary cohort:

The primary cohort will include the women and men who are expected to be most significantly impacted by the intervention, and this group is specifically defined by

• Presenting complaints suggestive of ACS
• At least one cTn measurement within 24 hours of admission
• A peak cTn value between the current sex-uniform manufacturer-derived 99th percentile URL and the novel sex-and population-specific 99th percentile URLs for women and men.

Presenting complaints suggestive of ACS will be identified in hospital records by the following presenting complaints of "chest pain" (DR074), "angina pectoris" (DI20), "observation due to suspicion of myocardial infarction" (Z034), "myocardial infarction" (DI21), "abdominal and pelvic pain" (DR10), "pain in the throat and chest" (DR07), "dyspnea" (DR060), "reflux" (DK21), "ischemic heart disease" (DI22-DI25) and "observation due to suspicion of another cardiovascular disorder" (DZ035).

Study participants are included at their index admission, and subsequent admissions are evaluated in follow up analyses.

Exclusion criteria

• Age < 18 years
• Patients with discharge diagnoses with conditions like pericarditis, myocarditis, endocarditis, cardiomyopathy, valve disease, arrhythmia, heart failure, pulmonary embolism, respiratory diseases, infectious diseases, digestive system diseases excluding reflux, digestive system diseases, diseases of the urinary and reproductive organs, and diseases of bones, muscles, and connective tissue, and do not have a discharge diagnosis of myocardial infarction or angina pectoris

The initial month following the implementation of the new sex-specific 99th percentile URLs will be excluded from consideration, as it will be seen as an adjustment period. Consequently, the intervention period will be extended by one month.