Heida, J. (Judith) (2016) Stability of vasopressin and copeptin ex-vivo. thesis, Medicine.
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Abstract
Abstract Background Arginine vasopressin (AVP) is a promising marker to predict renal disease progression. However, limited ex-vivo stability has been suggested, which in combination with a laborious assay led to the introduction of copeptin, an easy to measure surrogate marker for AVP. Literature states better ex-vivo stability of copeptin in comparison to AVP, although no study has formally investigated this issue. Therefore, we aimed to assess the effects of pre-analytic sample handling procedures on stability of AVP and copeptin. Methods Blood of ten healthy volunteers was collected in EDTA tubes. The effect of various pre-analytic sample handling procedures was investigated: immediate centrifugation at 800g, 2000g and 5000g, storage of whole blood and plasma at 25°C and 4°C for 2, 6 and 24 hours (h), prolonged frozen storage at -20°C, -80°C and -150°C, and lastly, the effect of repeated freeze-thaw cycles (1, 2 and 4 cycles). The maximal percentage change that can be explained by assay variability, i.e., the Acceptable Change Limit (ACL), was used as cut-off to determine relevant changes in AVP and copeptin. Results ACL was 25% and 19% for AVP and copeptin, respectively. Higher centrifugation speed resulted in lower AVP levels, whereas it did not affect copeptin levels. In whole blood, AVP was stable for 2h at 25°C and for 6h at 4°C, whereas in plasma, AVP was stable for 6h at 25°C. When stored at 4°C, AVP in plasma did not change for at least 24 hours. In contrast, copeptin levels were not affected at all by storage of whole blood and plasma at 4°C as well as 25°C for the total study duration. Both AVP and copeptin were stable up to at least one month when stored frozen at -20°C, -80°C or -150°C. AVP concentration decreased after 4 freeze-thaw cycles, whereas copeptin concentration was unaffected by repeated freeze-thaw cycles. Conclusion Pre-analytic sample handling conditions influenced AVP concentration considerably, while copeptin levels were not affected. Therefore, measuring copeptin as surrogate for AVP is an attractive alternative. In case measurement of AVP is chosen, a strict sample processing protocol for AVP is recommended.
| Item Type: | Thesis (Thesis) |
|---|---|
| Supervisor name: | Faculty supervisor: and Gansevoort, prof. dr. R. T. |
| Supervisor name: | Daily supervisors: and Zittema, Debbie and Ettema, Esmée and IJsselland Hospital, Capelle aan den IJsel and Department of Clinical Chemistry |
| Faculty: | Medical Sciences |
| Date Deposited: | 25 Jun 2020 10:44 |
| Last Modified: | 25 Jun 2020 10:44 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/551 |
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