Long-term biological variation in cardiac troponin I

Objectives: To determine the long-term biological variation (BV) of cardiac troponin I. Design and methods: Three samples separated by a mean of 8.7 +/- 2.8 months from 17 patients seen in an outpatient clinic. Tropoinin I was measured using a high sensitivity assay from Singulex, Inc. Results: The long-term analytical, intra-assay and total variation were 15.2%, 27.9%, and 70.9%, respectively. The index of individuality (II) was 0.45, and the reference change value was +98% and -50%, respectively. Conclusion: The BV over 9 months was comparable to previously published results over 2 months using the same testing methodology. The II indicates that reference range values are of less value than serial testing. (C) 2012 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.