Short-term variability in the measurement of plasma homocysteine, fasting and post-methionine loading

Objectives: Hyperhomocysteinemia is associated with premature cerebral, per ipheral and coronary vascular disease. Evaluation of the significance of ch anges in plasma total homocysteine (tHcy) results obtained by analysis of s erial specimens may be accomplished only by taking into account biologic (b etween-person and within-person) as well as analytical variation. Since the repeatability of a measurement significantly determines our ability to ass ociate tHcy level with the presence of disease, this study was performed to evaluate various components of variation in tHcy values. Design and methods: We report the within-person, between-person. and method ological variability of tHcy, both fasting and postmethionine load (PML) va lues, in 20 healthy volunteers from whom samples were drawn weekly for 4 we eks. Results: The short-term reliability coefficient (R) was 0.72 for fasting tH cy and 0.83 for PML tHcy. Conclusions: The current study demonstrates for the first time that the sho rt-term reliability coefficient for PML tHcy is relatively high (0.83), sug gesting that an individuals PML tHcy, like fasting tHcy, is relatively cons tant over at least one month, and that a single measurement should provide a reasonable characterization of an individual's PML tHcy concentration. (C ) 2001 The Canadian Society of Clinical Chemists. All rights reserved.