Evaluation of a Sensitive Copeptin Assay for Clinical Measurement

Abstract

Background: Copeptin, a marker of vasopressin production, has been introduced for earlier diagnosis of acute myocardial infarction and other clinical emergencies. We evaluated the analytical performance of a new generation co- peptin assay in an inter-laboratory trial. Methods: Precision, linearity range, carry-over contamination, the limit of blank and an inter-laboratory comparison trial for the copeptin US KRYPTOR assay were performed on the B·R·A·H·M·S KRYPTOR compact PLUS. Results: The intra-assay imprecision (CVs) was 12.6-2.2% and total imprecision over five days was 12.3-4.3% between 3.1 and 18.2 pmol/L. The assay had excellent linearity between 7-222 pmol/L. The limit of blank was 2.5 pmol/L and the limit of detection was 3.2 pmol/L, but was dependent on the analyte-free material used. No significant difference between sample type, such as serum or different types of plasma or reagent lots, was noted. The copeptin results remained un- changed upon five repeated freeze-thaw cycles. A set of patient samples with a mean copeptin concentration of 2.1-61 pmol/L run at two separate sites showed close correlation (r 2 =0.99, slope=1.01, intercept=0.35), indicating comparable re- sults across laboratories. Conclusion: The new ultrasensitive copeptin KRYPTOR assay shows excellent inter-lab precision, opening up the possi- bility for international guidelines to exclude acute myocardial infarction.