Two reviews being published in Annals of Internal Medicine address the challenges associated with using troponin levels to diagnose cardiac disease in patients with chronic kidney disease (CKD). Cardiac troponins (troponin I and T) are muscle contraction regulatory proteins found almost exclusively in the heart and are the most useful biomarkers of cardiac injury. Patients with CKD have a high prevalence of elevated serum troponin levels, even without cardiac disease, making it difficult to interpret their diagnostic and prognostic significance. Researchers conducted two systematic reviews of published evidence to evaluate the utility of troponin in both CKD patients with or without acute coronary syndrome (ACS). In the first paper, researchers systematically reviewed 98 observational studies to determine the prognostic value of troponin in patients who had CKD but not ACS. They found elevated levels of troponin I or troponin T were associated with worse prognosis. Specifically, patients with elevated troponin levels had a 2-4-fold higher risk for all-cause mortality, cardiovascular-specific mortality, and major adverse cardiac events.
In the second paper, researchers systematically reviewed 23 studies to determine if troponin levels could inform diagnosis, management, and prognosis of CKD patients who also had ACS. They found that troponin levels could help to identify patients with poor prognosis, but their value must be considered in the context of other clinical factors. The evidence was unclear whether troponin levels could help to diagnose ACS in patients with CKD. The studies did not evaluate whether troponin measures could help reclassify patients into high- and low-risk groups that may require different treatment.
The authors of an accompanying editorial caution that measuring troponins in CKD patients with a low pretest probability of coronary disease is likely to result in many false positive results and the value of obtaining troponin levels to inform evaluation and management is still unclear. For patients with ACS, troponin levels may be fore useful for ruling out myocardial infarction than for diagnosing it. The editorialists recommend further research to identify optimal cut-points for troponin levels in various patient populations and suggest testing management strategies based on these levels.