Impact of inflammation on the biomarkers of iron status in a cross-sectional survey of Lao women and children

Abstract

Anaemia is prevalent in South East Asia and Fe deficiency (ID) is considered to be the main cause, but the role of subclinical inflammation in the aetiology is uncertain. In the present study, we determined the influence of inflammation on the biomarkers of Fe status in women and children, and herein, we discuss the proportion of anaemia associated with ID. As part of the 2006 Lao People's Democratic Republic (The Lao PDR) National Nutrition Survey, blood collected from 482 young children and 816 non-pregnant women was analysed. Plasma ferritin, transferrin receptor (sTfR), Hb, C-reactive protein (CRP) and a-1-acid glycoprotein (AGP) concentrations were measured. ID was assessed using ferritin concentrations (, 12 (children) or ,15 (adults) mg/l), sTfR concentrations (. 8·3 mg/l) and body Fe stores (BIS , 0). Elevated CRP (. 5 mg/l) and/or AGP (.1 g/l) concentrations were used to categorise inflammation status in order to correct the Fe biomarkers for inflammation. Inflammation was present in 14 % of adults and 43 % of children. Anaemia was present in 37·6 % of both women (Hb concentrations ,120 g/l) and children (Hb concentrations ,110 g/l). Correcting ferritin concentrations for inflammation increased the prevalence of ID from 24·3 to 26 % for women and from 18 to 21 % for children (P,0·001 for both). Ferritin concentrations were more helpful in detecting ID than sTfR concentrations or BIS, but regression analysis found that sTfr concentrations explained more of the variance in Hb concentrations in both women (20 %) and children (17 %) than ferritin concentrations (5 and 1·4 %, respectively). Nevertheless, the total variance in Hb concentrations explained was only 26 and 18 % in women and children, respectively, and other factors may be more important than ID in contributing to anaemia in The Lao PDR.

Adjusting soluble transferrin receptor concentrations for inflammation: Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project

“…CRP is highly responsive to the rise in cytokines at the start of an acute-phase response, and elevations in both CRP and cytokine concentrations suppress erythropoietin production, thereby preventing the elevation of plasma and serum concentrations of sTfR, which results in a temporary but complete shutdown of normal iron metabolism (30). In addition, the magnitude of the difference in iron-deficient erythropoiesis was minimal when adjusting for CRP, which is a finding that was previously shown (31, 32). Although sTfR is not an APP, it may be affected by inflammation through alternative mechanisms.…”

Iron deficiency in early pregnancy using serum ferritin and soluble transferrin receptor concentrations are associated with pregnancy and birth outcomes

“…Similar to the current study, others have found differences in the prevalence and risk factors for ID depending on which iron measure is used to define ID. 7,[27][28][29][30] The present study found that 15.3% of women were defined as ID using all three definitions. Although the three iron indicators showed relatively good agreement for ID prevalence and identified similar groups at highest risk of ID, the different estimates of ID prevalence demonstrates that different iron measures reflect a slightly different aspect of iron metabolism.…”

Dietary iron intake, iron status, and gestational diabetes

“…Although hepcidin has been gaining attention as the master regulator of iron homeostasis, the question of which indicators are the most optimal for measuring iron status remains subject to debate. sTfR was previously considered more useful for measuring iron status in the presence of inflammation, yet emerging evidence suggests that its concentrations also increase with infection or high a(1)-acid glycoprotein or CRP concentrations (16,17,49). Additional work is, therefore, needed to identify the most appropriate indicators to assess iron status and homeostasis, as well as to characterize high iron status during pregnancy.…”

“…Hepcidin, the central regulator of iron homeostasis, is upregulated by inflammatory stress response pathways leading to decreased dietary iron absorption and the sequestering of iron in hepatocytes and macrophages (15). Circulating concentrations of iron markers, such as ferritin and transferrin receptors, may also increase in the presence of infection or inflammation, further complicating the accurate estimation of iron status in human populations (16,17).…”