title: Discrimination ratio analysis of inflammatory markers: implications for the study of inflammation in chronic disease.
abstract: To understand the role of inflammation in chronic disease it is important to have a reliable measure of habitual inflammatory status. A number of acute-phase response markers have been used as measures of inflammatory status, but the ability of a single measure to appropriately reflect habitual inflammatory status has not been assessed. This study compares the ability of different inflammatory markers to characterize habitual inflammatory status in overweight women. A single fasting blood sample was taken from 86 overweight women (mean body mass index [BMI], 35.2 kg/m2; range, 26.2 to 47.6 kg/m2) and a number of inflammatory markers (both acute-phase response markers and cytokines) were measured. A randomly selected subpopulation of 15 women attended on 2 further occasions for further blood samples. Using the subpopulation, discrimination ratios (DRs) were calculated for each inflammatory marker to assess the within-subject variability. The DRs were then used to determine the relationship between these markers, adjusted for within-subject variability, in the whole population. In this highly controlled experimental environment, interleukin-6 (IL-6), with a DR of 3.71, was the cytokine with the greatest ability to discriminate between subjects, suggesting that it is best able to characterize habitual inflammatory status. Sialic acid was the acute-phase response marker with the highest DR (3.16), and showed stronger correlations with other inflammatory markers, including C-reactive protein (CRP), than IL-6. This study suggests that use of some inflammatory markers, such as CRP, with large within-individual variability, will underestimate the relationship between inflammation and disease, and thus relationships between inflammation and chronic disease may be stronger than previously appreciated. Future studies should consider IL-6 or sialic acid to provide a more robust measure of inflammatory status.
authors.affiliation: The Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK.
authors.forename: L M
authors.initials: LM
authors.lastname: Browning
authors.forename: J D
authors.initials: JD
authors.lastname: Krebs
authors.forename: S A
authors.initials: SA
authors.lastname: Jebb
mesh_terms: D000209:Acute-Phase Proteins / Q000378:metabolism; D000328:Adult; D000368:Aged; D000465:Algorithms; D015415:Biomarkers / Q000032:analysis*; D015992:Body Mass Index; D001835:Body Weight; D002097:C-Reactive Protein / Q000032:analysis / Q000378:metabolism; D002908:Chronic Disease; D016207:Cytokines / Q000097:blood; D005260:Female; D006801:Humans; D007249:Inflammation / Q000378:metabolism*; D008875:Middle Aged; D019158:N-Acetylneuraminic Acid / Q000097:blood; D009765:Obesity / Q000378:metabolism
chemical_list: D000209:Acute-Phase Proteins; D015415:Biomarkers; D016207:Cytokines; D002097:C-Reactive Protein; D019158:N-Acetylneuraminic Acid