title: Methods for determining "reference changes" from serial measurements: plasma lipid-bound sialic acid.
abstract: Lipid-bound sialic (neuraminic) acid (LSA) was measured in EDTA-treated plasma of 26 healthy subjects at three-month intervals for up to one year. The change in LSA concentration for consecutive measurements ranged from -54 to 42 mg/L (mean, -2.1 mg/L; SD, 19.6 mg/L; n = 56). The "reference change" for plasma LSA (+/- 2 SD), calculated from distribution of the differences, was +/- 39 mg/L. The 88th percentile of the intra-individual variance was 338 mg2/L2 and the mean variance was 159 mg2/L2. Using the homeostatic, autoregressive time-series model, a reference change of +/- 51 mg/L between two consecutive measurements was determined to be statistically significant (i.e., expected by chance no more than 5% of the time) in 88% of the healthy subjects. Only 73% of the healthy subjects would have had intra-individual variances corresponding to the reference change of +/- 39 mg/L according to the autoregressive model. The concentration of LSA in plasma was significantly decreased upon surgery in five of 10 patients with colorectal adenocarcinomas of Dukes stages A-C when we used +/- 39 mg/L as the reference change, but in only two of the 10 when we used +/- 51 mg/L as the reference change.
authors.affiliation: Department of Laboratory Medicine, University of Texas M. D. Anderson Cancer Center, Houston 77030.
authors.forename: S
authors.initials: S
authors.lastname: Shahangian
authors.forename: H A
authors.initials: HA
authors.lastname: Fritsche
authors.forename: J I
authors.initials: JI
authors.lastname: Hughes
authors.forename: D A
authors.initials: DA
authors.lastname: Johnston
mesh_terms: D000230:Adenocarcinoma / Q000097:blood / Q000601:surgery; D000368:Aged; D015179:Colorectal Neoplasms / Q000097:blood / Q000601:surgery; D005260:Female; D006801:Humans; D008055:Lipids / Q000097:blood*; D008297:Male; D008875:Middle Aged; D019158:N-Acetylneuraminic Acid; D012016:Reference Values; D012794:Sialic Acids / Q000097:blood*
chemical_list: D008055:Lipids; D012794:Sialic Acids; D019158:N-Acetylneuraminic Acid