title: Minimal inflammation, acute phase response and avoidance of misclassification of vitamin A and iron status in infants--importance of a high-sensitivity C-reactive protein (CRP) assay.
abstract: The acute phase response is known to affect many biological parameters used to assess the iron and vitamin A status. Usually, C-reactive protein (CRP) values higher than 5 to 10 mg/L are taken as indicative of this response. Here we report changes occurring at much lower CRP values. A range of parameters (clinical chemistry, retinol, vitamin E, carotenoids, thyroid status, blood count, immunology) were measured in 101 healthy one-year-old children with no or only minimal symptoms of airway infection and CRP values below 6 mg/L on routine testing. Additionally, CRP values were measured by a high-sensitivity assay (detection limit 0.2 mg/L). When determined by a more sensitive assay, CRP values (median, 0.26 mg/L) revealed highly significant associations with parameters known to be influenced by the acute phase response. Using a limit of 0.6 mg/L (75th percentile), significantly lower levels were observed for transthyretin, iron, retinol, and beta-carotene in the group with the higher CRP levels. This relationship was confirmed intra-individually in a subgroup of 21 children who underwent a second blood draw about four weeks after the first one. The acute phase response is triggered at very low inflammatory levels with CRP values considerably lower than 5 to 10 mg/L, and can occur in apparently healthy children. A high-sensitivity CRP assay is necessary to detect this low level, and in the case of iron or vitamin A, it can help to avoid misclassification of the nutritional status.
authors.affiliation: Department of Pediatric Pneumology and Immunology, University Clinic Charité, Humboldt University Berlin, Berlin, Germany. klaus.abraham@charite.de
authors.forename: Klaus
authors.initials: K
authors.lastname: Abraham
authors.forename: Christian
authors.initials: C
authors.lastname: Müller
authors.forename: Anette
authors.initials: A
authors.lastname: Grüters
authors.forename: Ulrich
authors.initials: U
authors.lastname: Wahn
authors.forename: Florian J
authors.initials: FJ
authors.lastname: Schweigert
mesh_terms: D000210:Acute-Phase Reaction / Q000097:blood*; D018798:Anemia, Iron-Deficiency / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis / Q000378:metabolism*; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007501:Iron / Q000097:blood*; D008297:Male; D009752:Nutritional Status; D012141:Respiratory Tract Infections / Q000097:blood; D016036:Seroepidemiologic Studies; D014801:Vitamin A / Q000097:blood*; D014802:Vitamin A Deficiency / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology
chemical_list: D015415:Biomarkers; D014801:Vitamin A; D002097:C-Reactive Protein; D007501:Iron