title: Within-subject variation of elastase/alpha 1-protease inhibitor complexes and lactoferrin in plasma.
abstract: Several studies have shown increased plasma concentrations of neutrophil elastase in complex with alpha 1-protease inhibitor and/or lactoferrin in inflammatory conditions, and serial measurements have been advocated in order to follow disease activity. However, data on the magnitude of the within-subject variation are necessary for evaluation of the significance of changes in results obtained on analysis of serial samples. Within-subject variation of elastase/alpha 1-protease inhibitor complexes and lactoferrin over a short time was studied in six young men who had blood samples drawn every 4 h over 2 days. Within-subject variation over a longer time was investigated in 12 healthy adults, 6 females and 6 males, who had blood samples drawn in the morning once a week for 10 weeks. From five of the females and five of the males, blood samples were also drawn every morning on 5 consecutive days during 1 week. Within-subject variations over hours, days, and weeks were estimated as 0.050, 0.124, and 0.148 for elastase/alpha 1-protease inhibitor complexes and as 0.101, 0.119, and 0.143 for lactoferrin. A tendency towards variation of LAC with menstrual cycle in fertile females was noticed. From within-subject variation, between-subject variation and analytical variation, indices of individuality were calculated as 1.1 and 1.8 for elastase/alpha 1-protease inhibitor complexes and lactoferrin, respectively. This means that within-subject variation for lactoferrin is quite small compared to between-subject variation, and the usefulness of reference limits is very limited, when interpreting results from individual patients. For elastase/alpha 1-protease inhibitor complexes, the use of reference limits might be more appropriate, although still not optimal.
authors.affiliation: Department of Clinical Chemistry, Odense University Hospital, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Antonsen
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007781:Lactoferrin / Q000097:blood*; D007958:Leukocyte Count; D019272:Leukocyte Elastase; D008297:Male; D008598:Menstruation / Q000502:physiology; D008875:Middle Aged; D010196:Pancreatic Elastase / Q000097:blood*; D012016:Reference Values; D000515:alpha 1-Antitrypsin / Q000378:metabolism*
chemical_list: D000515:alpha 1-Antitrypsin; D007781:Lactoferrin; D010196:Pancreatic Elastase; D019272:Leukocyte Elastase