Identifying delayed separation in plasma homocysteine specimens
Chen, M.; Nuttall, K.L.
Annals of Clinical and Laboratory Science 29(4): 316-319
1999
ISSN/ISBN: 0091-7370 PMID: 10528832 Document Number: 506905
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.