Key result
In stable haemodialysis patients, within-subject biological variation was 10.5% for hs-cTnT and 20.2% for cTnI, with low indices of individuality limiting the value of population-based decision points.
Why the study?
What is the biological variation of hs-cTnT and cTnI in stable haemodialysis patients?
Observational (n=18)
What is the biological variation of hs-cTnT and cTnI in stable haemodialysis patients?
In stable haemodialysis patients, the low index of individuality for hs-cTnT and cTnI indicates that serial measurements, rather than population-based cutoffs, are necessary to diagnose myocardial infarction.
Supports serial troponin interpretation over fixed cutoffs in haemodialysis; leaves open prospective validation for MI diagnosis.
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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Mbagaya et al. (2015) conducted an observational in End-stage renal failure on stable haemodialysis (n=18). hs-cTnT and cTnI assays was evaluated on Biological variation (analytical CV, within-subject CV, between-subject CV, reference change value, and index of individuality). In stable haemodialysis patients, within-subject biological variation was 10.5% for hs-cTnT and 20.2% for cTnI, with low indices of individuality limiting the value of population-based decision points.
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