title: The use of adjustment factors to address the impact of inflammation on vitamin A and iron status in humans.
abstract: Many nutrient biomarkers are altered by inflammation. We calculated adjustment factors for retinol and ferritin by using meta-analyses of studies containing the respective biomarker and 2 acute phase proteins in serum, C-reactive protein (CRP), and α1-acid glycoprotein (AGP). With the use of CRP and AGP we identified 4 groups in each study: reference (CRP ≤5 mg/L, AGP ≤1 g/L), incubation (CRP >5 mg/L, AGP ≤1 g/L), early convalescence (CRP >5 mg/L, AGP >1 g/L), and late convalescence (CRP ≤5 mg/L, AGP >1 g/L). For each biomarker, ratios of the geometric means of the reference to each inflammation group concentration were used to calculate adjustment factors for retinol (1.13, 1.24, and 1.11) and ferritin (0.77, 0.53, and 0.75) for the incubation, early, and late convalescent groups, respectively. The application of the meta-analysis factors in more recent studies compares well with study-specific factors. The same method was used to calculate adjustment factors for soluble transferrin receptor (sTfR) and body iron stores (BISs) in Lao children. We found no advantage in adjusting sTfR for inflammation; in fact, adjustment decreased iron deficiency. Neither adjusted (10% <0 mg/kg) nor nonadjusted (12% <0 mg/kg) BISs detected as much iron deficiency as did ferritin (18% <12 μg/L) and adjusted ferritin (21% <12 μg/L) unless the cutoff for BISs was increased from 0 to <3 mg/kg. However, we could find no evidence that the larger number of children identified as having BISs <3 mg/kg had risks of anemia comparable to those identified by using ferritin <12 μg/L. In conclusion, both corrected and uncorrected ferritin concentrations <12 μg/L are associated with more iron deficiency and anemia than either sTfR >8.3 mg/L or BISs <0 mg/kg in Lao children.
authors.affiliation: Northern Ireland Centre for Food and Health, School of Biomedical Sciences, University of Ulster, Coleraine, United Kingdom; di.thurnham@ulster.ac.uk.
authors.forename: David I
authors.initials: DI
authors.lastname: Thurnham
authors.affiliation: Nutrition Consultant, Little Wilbraham, Cambridge, United Kingdom; and.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Northrop-Clewes
authors.affiliation: Public Nutrition Solutions Ltd, Bangkok, Thailand.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Knowles
mesh_terms: D018798:Anemia, Iron-Deficiency / Q000453:epidemiology / Q000276:immunology* / Q000378:metabolism / Q000628:therapy; D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D003226:Congresses as Topic; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood; D012306:Risk; D014802:Vitamin A Deficiency / Q000453:epidemiology / Q000276:immunology* / Q000378:metabolism / Q000628:therapy
chemical_list: D015415:Biomarkers; D018836:Inflammation Mediators
keywords: acute phase proteins; ferritin; iron; retinol; soluble transferrin receptor
references.citation: Am J Clin Nutr. 2011 May;93(5):1006-11
references.pmid: 21411617
references.citation: Crit Care Med. 1992 Jul;20(7):934-41
references.pmid: 1617986
references.citation: Lancet. 1999 Jul 17;354(9174):203-9
references.pmid: 10421302
references.citation: Br J Nutr. 1999 Mar;81(3):191-201
references.pmid: 10434845
references.citation: Blood. 2003 Aug 1;102(3):783-8
references.pmid: 12663437
references.citation: Ann Clin Biochem. 2008 Jan;45(Pt 1):18-32
references.pmid: 18275670
references.citation: Lancet. 2003 Dec 20;362(9401):2052-8
references.pmid: 14697804
references.citation: Ann Clin Biochem. 1988 Jan;25 ( Pt 1):60-6
references.pmid: 2451463
references.citation: Br J Nutr. 2008 Jul;100(1):174-82
references.pmid: 18177514
references.citation: Am J Clin Nutr. 2000 Jun;71(6):1582-8
references.pmid: 10837302
references.citation: Am J Clin Nutr. 1996 Jul;64(1):94-100
references.pmid: 8669421
references.citation: Br J Nutr. 2003 Aug;90(2):353-61
references.pmid: 12908896
references.citation: J Nutr. 2012 Jan;142(1):105-11
references.pmid: 22157541
references.citation: J Blood Med. 2013 Mar 20;4:11-22
references.pmid: 23687454
references.citation: Proc Nutr Soc. 2005 Nov;64(4):502-9
references.pmid: 16313694
references.citation: Am J Clin Nutr. 1995 Aug;62(2):434-8
references.pmid: 7542831
references.citation: Am J Clin Nutr. 2010 Sep;92(3):546-55
references.pmid: 20610634
references.citation: Am J Clin Nutr. 2000 Nov;72(5):1164-9
references.pmid: 11063444
references.citation: Ann Clin Biochem. 2000 May;37 ( Pt 3):289-97
references.pmid: 10817241
references.citation: Arch Dis Child. 1988 Feb;63(2):115-7
references.pmid: 3126717
references.citation: Med Clin North Am. 1976 Jul;60(4):831-49
references.pmid: 775222
references.citation: J Nutr. 2004 Nov;134(11):3127-32
references.pmid: 15514286
references.citation: Trans R Soc Trop Med Hyg. 1991 Mar-Apr;85(2):194-9
references.pmid: 1909468
references.citation: Br J Nutr. 2013 Dec;110(12):2285-97
references.pmid: 23778021
references.citation: Br J Nutr. 1998 Nov;80(5):451-6
references.pmid: 9924267
references.citation: Am J Clin Nutr. 1998 Jun;67(6):1237-43
references.pmid: 9625099
references.citation: Blood. 2003 May 1;101(9):3359-64
references.pmid: 12521995
references.citation: Ann Clin Biochem. 1992 Mar;29 ( Pt 2):123-31
references.pmid: 1378257
references.citation: Eur J Clin Invest. 1998 Jul;28(7):520-7
references.pmid: 9726030