Methodological assessment of assays for red cell sodium concentration and sodium-dependent lithium efflux

Document Type

Article

Publication Date

11-11-1981

Abstract

Assays for red cell sodium concentration and sodium-dependent lithium efflux were studied from a methodological point of view. The technical errors for sodium concentration-based on concurrent analysis of randomized blind duplicate samples -was 2.5% and for lithium efflux 6.4%. Based on repeated measures in the same individual, the assays were stable over time and reproducible; individual differences at a mean interval of 16 days were not significantly different. A wait of two hours from time of phlebotomy to analysis yielded a slight (3.8%) but significant fall in the sodium concentration; no further change was found at four hours. No change occurred in the lithium efflux over time. A standardized breakfast containing 664 mg sodium did not affect the measurements when fasting and three-hour postprandial levels were compared. The ratios of intra- to inter-individual variances were small-0.04 for red cell sodium concentration and 0.09 for sodium-stimulated lithium efflux. These assays appear to be reproducible and stable and can be applied in large scale field trials. © 1981.

Publication Source (Journal or Book title)

Clinica Chimica Acta

First Page

319

Last Page

329

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