Biological variation of cardiac troponin in stable haemodialysis patients
Wycliffe Mbagaya1, Ahai Luvai2, Berenice Lopez3
1Weston General Hospital, Weston-Super-Mare, UK mbagaya@doctors.org.uk.
Insights
Diagnosing myocardial infarction in dialysis patients requires serial cardiac troponin (cTn) measurements due to chronic cTn elevation. Biological variation data for high-sensitivity troponin T (hs-cTnT) and troponin I (cTnI) assays confirm this need.
Area of Science:
- Clinical Chemistry
- Cardiology
- Nephrology
Background:
- Patients with end-stage renal failure often have chronically elevated serum cardiac troponin (cTn) levels.
- Distinguishing acute myocardial infarction from chronic elevation is crucial for accurate diagnosis in this population.
- This study investigates biological variation of cTn assays in stable haemodialysis patients.
Purpose of the Study:
- To collect biological variation data for high-sensitivity troponin T (hs-cTnT) and troponin I (cTnI) assays.
- To inform the optimal use of cTn assays for diagnosing myocardial infarction in end-stage renal failure patients.
- To compare assay performance in stable haemodialysis patients.
Main Methods:
- Recruited 18 stable haemodialysis patients; 16 completed the 10-week study.
- Collected weekly predialysis blood samples during the second dialysis session.
- Determined analytical coefficient of variation (CVA), within-subject biological variation (CVI), between-subject biological variation (CVG), reference change value (RCV), and index of individuality (II) for both hs-cTnT and cTnI assays.
Main Results:
- All hs-cTnT samples exceeded the 99th percentile for healthy individuals; 29.4% of cTnI samples did.
- hs-cTnT: CVA 2.1%, CVI 10.5%, CVG 64.2%, RCV 28.1%.
- cTnI: CVA 7.1%, CVI 20.2%, CVG 100.5%, RCV 79.8%. Index of individuality (II) was 0.17 for hs-cTnT and 0.2 for cTnI.
Conclusions:
- Long-term biological variation of cTn in haemodialysis patients mirrors that in healthy individuals and stable coronary artery disease patients.
- Low index of individuality (II) for both hs-cTnT and cTnI indicates limited value of population-based decision points.
- Serial cTn measurements are essential for detecting significant changes and diagnosing myocardial infarction in this cohort.
Background:
Patients with end-stage renal failure exhibit a chronic elevation of serum cardiac troponin (cTn) concentration. In order to facilitate the diagnosis of myocardial infarction in these patients, it is necessary to distinguish an increased cTn concentration due to an acute event, from that being a manifestation of chronic elevation. The aim of this study was to gather biological variation data relating to two serum cTn assays, one, a hs-cTnT assay, the other a contemporary sensitive cTnI assay, among stable haemodialysis patients. It was hoped that this might inform as to the best way to use cTn assays to assist in the diagnosis of myocardial infarction in patients with end-stage renal failure.
Methods:
Eighteen stable haemodialysis patients were recruited, of whom 16 completed the study. Predialysis blood samples were collected weekly for 10 weeks during the second dialysis session of the week. Analytical CV (CVA), within-subject biological variation (CVI), between-subject biological variation (CVG), reference change value (RCV) and index of individuality (II) were determined for both assays.
Results:
All samples had a serum hs-cTnT concentration above the 99th percentile for a healthy population compared to 29.4% for cTnI. For hs-cTnT, the long-term CVA was 2.1%, CVI 10.5%, CVG 64.2%, RCV 28.1% and log-normal RCV (rise/fall) 34.4%/-25.6%. The corresponding values for cTnI were 7.1, 20.2, 100.5 and 79.8%/-44.4%. The II was 0.17 and 0.2 for hs-cTnT and cTnI, respectively.
Conclusion:
Long-term biological variation of cTn in stable haemodialysis patients is similar to that in healthy individuals and in patients with stable coronary arterial disease. The low II for cTnI and hs-cTnT in stable haemodialysis patients indicates that population-based decision points are of limited value. Serial measurements are required to detect significant changes in cTn concentrations and support diagnosis of myocardial infarction in these patients.
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