Reply to H Jang and M Jeon (original) (raw)
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Iron Absorption Prediction Equations Lack Agreement and Underestimate Iron Absorption1,2
2000
A number of algorithms have been developed to predict the bioavailability of iron from mixed meals and diets, but their direct validity in predicting change in iron status remains questionable. Throughout the course of conducting a large feeding trial in 10 convents in Manila, we collected weighed food intake data (n ¼ 317) and directly compared the performance of these prediction equations to each other and to the change in serum ferritin (SF). Dietary weighed food intakes were measured on d 3 every 2 wk for each woman and iron status determined at baseline, 4.5 mo, and 9 mo. The Monsen and Balintfy equation predicted higher median absorption efficiency (7.3%) than did the equations of Hallberg and Hulthen (6.1%) and Reddy et al. (5.8%). In contrast, the predictions that used the equations of Bhargava et al. (3.8%), Tseng et al. (2.9%), and Du et al. (2.6%) were significantly lower. The iron absorption efficiencies calculated using the Monsen and Balintfy equation correlated with those using the Hallberg and Hulthen equation (r ¼ 0.91, P , 0.001). This slope did not differ from unity, whereas all other equations underestimated iron absorption efficiency relative to Monsen and Balintfy's equation. The median efficiency of absorption, based on change in SF in 114 subjects, was 17.2%, suggesting that these equations underestimate iron absorption. The inhibitory and enhancing factors in the published prediction equations were quantitatively either too large or
Biological Trace Element Research, 2013
Although a 40 % absorption of a standard reference dose corresponds to iron (Fe) absorption in borderline Fedeficient subjects, this percentage is currently applied to all subjects independent of Fe status: (a) to assess the use of the 40 % of Fe absorption of the reference dose (FeRD%) for subjects with iron-depleted stores (IDS), normal Fe status (NIS), Fe deficiency without anemia (IDWA), and Fe deficiency anemia (IDA) and (b) to explore relationships between Fe status biomarkers and FeRD%. Six hundred forty-six participants (582 women and 64 men) were selected from multiple Fe bioavailability studies and classified into four groups based on Fe status: NIS, IDS, IDWA, and IDA. All men were classified as normal. The absorption from FeRD% was calculated in each group and correlated with Fe status biomarkers. (a) Women with IDS absorbed 40 (18.9-84.7)% of the reference dose; (b) for male subjects with NIS, the absorption of the reference dose was 19 (9.8-36.1)%, while for females, absorption was observed as to be 34 (16.7-68.6)%. In the case of subjects with IDWA, a 43 (19.7-92.5)% absorption was observed, while subjects with IDA demonstrated 67 (45.2-98.6)% absorption. Serum ferritin (SF) had the strongest inverse correlation with FeRD% (r =−0.41, p <0.001). A transferrin saturation (TS) <15 % increases the probability that the FeRD% will be highly elevated (OR, 5.05; 95 % CI, 2.73, 9.31; p <0.001). A 40 % absorption as reference dose is only appropriate to assess Fe absorption in subjects with IDS and IDWA. SF had an inverse correlation with FeRD%, and TS increases the probability that the FeRD% will be elevated by over fivefold.
Quantification of unlabelled non-haem iron absorption in human subjects: a pilot study
British Journal of Nutrition, 2003
A method for measuring unlabelled Fe absorption has been investigated in a pilot study using a simple mathematical model. The metabolism of newly absorbed Fe can be approximated as a single-compartment model with the sampled compartment being the plasma pool. Five female volunteers (aged 30–55 years) were recruited to participate in the pilot study. After a 10 mg oral dose of unlabelled ferrous sulfate, the change in plasma Fe concentration over the following 6 h was used to estimate the quantity of absorbed Fe from the mathematical model. To assess the accuracy of the new technique, a 1 mg oral dose of 57Fe-labelled iron sulfate was given simultaneously with a 225 μg intravenous dose of 58Fe as iron citrate. The plasma appearance of the labelled Fe was used to estimate the absorption of the oral label from the traditional area under the curve method. There was no significant difference (P=0·61) between the geometric mean absorption of the unlabelled (19 (- 1 sd 12, +1 sd 28) %) and...
1988
The percent absorption of iron from four dietary sources was compared in 2018 human subjects with three indicators of iron status, serum ferritin concen tration, percent saturation of plasma transferrin and iron absorption from a reference dose of ferrous sulfate. Higher correlation coefficients (r) were obtained by comparing di etary iron absorption with the reference dose absorption rather than with serum ferritin; for example, r = +0.61 and r = -0.38, respectively, for a meat and vegetable meal. However, in practice serum ferritin is almost as ef ficient as the reference dose absorption in estimating di etary iron absorption, because the 95% confidence limits calculated from the regression equations were very similar. The values of r calculated for iron absorption versus trans ferrin saturation were comparable to those obtained with the other indicators only in the range of transferrin satu ration values below 25%, whereas in more iron-replete sub jects (transferrin saturation > 25%), this correlation vir tually disappeared. This indicates that, although both serum ferritin and transferrin saturation reflect iron status in irondepleted subjects, the control of iron absorption in ironreplete subjects is more dependent on iron stores as re flected in the serum ferritin concentration than the percent saturation of transferrin.
Estimation of Iron Overload-Implications of its Non-linear Correlation
Journal of Blood Disorders & Transfusion, 2016
Thalassaemias and haemoglobinopathies contribute the highest number of cases, as far as single gene disorders are concerned, where blood transfusion and iron chelation remain the mainstays of therapy. Depending upon the requirement of transfusion, thalassaemias have been classified into two categories: 1) Transfusion dependent, 2) Non-transfusion dependent. Non-transfusion dependent thalassaemia patients, contrary to previous belief, suffer from iron overload. If this iron is estimated by the level of ferritin in serum, it does not linearly correlate to hepatic and/or cardiac iron. It was noted during our study that serum ferritin levels up to 300 ng/ml correlated with hepatic iron load of up to 3 mg/g of DLT almost linearly, within +0.5 SD of mean. There were a few patients in whom the serum ferritin level compared to the corresponding hepatic iron content (as measured by MRI) was more than +1.0 SD, and in some patients it was even ≥ 2.5 SD. In addition to serum ferritin, which is also a marker of acute inflammation, CRP was also estimated. It was seen that in these patients, CRP was also high. They were investigated for Hepatitis B, C and work ups were done for Tuberculosis. Out of the 350 such patients who were examined, 18 patients (5.14%) had their level of serum ferritin ≥ 1.0 SD, 08 tested positive for Tuberculosis, and 05 tested Positive for Hepatitis C and 01 for Hepatitis B. 14 patients out of the 18 (77.77%), who were screened to be out of the limits of SD had some infectious pathology in addition to their primary disorder, which was detected due to this observed discrepancy. They are undergoing treatment as appropriate for the diagnosis. In conclusion, in the range where the level of serum ferritin is linearly correlated to the corresponding hepatic iron, the value was >1.0 SD of mean, clinical investigations should be done to exclude possibilities of infections like Hepatitis and Tuberculosis.
Revaluating serum ferritin as a marker of body iron stores in the traceability era
Clinical Chemistry and Laboratory Medicine (CCLM), 2012
Serum ferritin is used for diagnosing iron-related disorders. However, most studies validating this application were performed before the introduction of the 2nd and 3rd WHO International Standards (ISs) to harmonize assay results. We revised the available literature to evaluate if consolidated clinical applications of ferritin and recommended cut-offs have been validated using ISs calibrated assays. All Medline retrieved reviews and individual studies performed since ISs availability were selected and analyzed according to predefined criteria. Concerning ferritin and iron deficiency (ID), only one review, including studies published before 1988, met established criteria. Results showed that ferritin can effectively rule out ID anemia in patients with or without inflammatory disease at cut-offs of 70 and 40 μg/L, respectively. From two studies using ISs calibrated assays that met inclusion criteria, no information emerged on which cut-off should be employed to obtain similar sensiti...
Title : Iron bioavailability from commercially available iron supplements
2015
Affiliations: Tatiana Christides, Department of Life and Sports Science, Faculty of Engineering & Science, University of Greenwich, United Kingdom David Wray, Department of Pharmaceutical, Chemical & Environmental Sciences, Faculty of Engineering & Science, University of Greenwich, United Kingdom Richard McBride, Department of Life and Sports Science, Faculty of Engineering & Science, University of Greenwich, United Kingdom Rose Fairweather, Diabetes & Nutritional Sciences Division, School of Medicine, King's College London, United Kingdom Paul Sharp, Diabetes & Nutritional Sciences Division, Metal Metabolism Group, School of Medicine, King's College London, United Kingdom