title: Identifying delayed separation in plasma homocysteine specimens.
abstract: The delayed separation of plasma from the cellular components of blood can lead to falsely elevated homocysteine results. The incidence of delayed separation in patient specimens was examined by using the ratio of arginine to the sum of arginine plus ornithine [arg/(arg + orn)], a ratio <0.50 being consistent with delayed separation. Two groups were examined: 1) low homocysteine (<10 micromol/L, n = 10), and 2) elevated (>18 micromol/L, n = 12). Specimens in the low group showed an average ratio of 0.47, with 6 of 10 <0.50. In contrast, specimens in the elevated group showed an average ratio of 0.31, with 11 of 12 <0.50. Characteristics consistent with delayed separation occurred frequently, but were significantly more frequent (p = 0.009) in the elevated group. This suggests that many homocysteine results may be falsely elevated due to preanalytic collection problems.
authors.affiliation: Department of Pathology, University of Utah School of Medicine, Salt Lake City 84132, USA.
authors.forename: M
authors.initials: M
authors.lastname: Chen
authors.forename: K L
authors.initials: KL
authors.lastname: Nuttall
mesh_terms: D000328:Adult; D000368:Aged; D001120:Arginine / Q000097:blood; D001800:Blood Specimen Collection; D005189:False Positive Reactions; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009952:Ornithine / Q000097:blood; D013997:Time Factors
chemical_list: D006710:Homocysteine; D001120:Arginine; D009952:Ornithine