Background: Troponin I (TnI) is an effective marker for detecting myocardial injury, but the interpretation of levels in the setting of end-stage renal disease (ESRD) is still unclear. TnI levels have been noted to be increased in 5-18% of asymptomatic haemodialysis (HD) patients with standard assays, but newer-generation, high-sensitivity assays have not been examined. In addition, there is limited data on the variability of TnI levels in patients over time as well as the effect of HD on TnI levels. The aim of this study was to prospectively explore the incidence of TnI with a high-sensitivity assay, the variability of TnI levels over time and the effect of HD on levels.
Methods: We enrolled 51 asymptomatic HD patients and checked TnI levels using a high-sensitivity assay. Levels were drawn pre-HD monthly for three consecutive months. As per manufacturer guidelines, levels were considered normal up to 0.034 ng/mL, indeterminate elevation (IE) if between 0.035 and 0.120 ng/mL and consistent with myocardial infarction (MI) if >0.120 ng/mL. In the third month, post-HD TnI was also drawn to determine change with dialysis.
Results: At baseline, median TnI level was 0.025 ng/mL (range, 0-0.461 ng/mL). Baseline TnI levels were normal in 63% and elevated (≥0.035 ng/mL) in 37%. Of those with elevations, 79% were in the IE range and 21% in the acute myocardial infarction range. Higher TnI levels at baseline were associated with a history of coronary artery disease, left ventricular hypertrophy, lower cardiac ejection fraction and higher serum phosphate levels. Average incidence of elevated TnI was 41% over the 3 months. Thirty-six patients had stable levels without a change in classification over 3 months. Twelve varied over time. Forty-five (94%) had no change in classification pre- and post-HD.
Conclusion: Using a new-generation, high-sensitivity assay, over a third of asymptomatic ESRD patients have an elevated TnI. The significance of these low-level elevations is unclear at this time. TnI levels remain stable over a 3-month period in most patients. HD treatment does not appear to affect the TnI level.