Reference distributions for serum iron and transferrin saturation: a practical, simple, and clinically relevant approach in a large cohort

Abstract

The principal considerations driving iron status evaluation are clinical concern for anemia and the possibility of iron-storage disease. Most often, the circulating levels of transferrin (or total iron binding capacity) and serum iron are measured and the percentage of transferrin saturation (TSAT) is then computed. Optimally, reference ranges for these analytes should exclude the effects of the acute phase response, nutritional status, estrogen effect, specific genetic disorders, liver disease, and blood transfusion. The current study reports reference ranges for serum iron and TSAT within a cohort of over 55,000 Caucasians from northern New England, tested in our laboratory between 1994 and 1999. Measurements were standardized against serum reference material (SRM) 937 (for iron) and certified reference material (CRM) 470 (also called reference preparation for proteins in human serum (RPPHS)) (for transferrin), and analyzed using a previously published approach. Individual cases with evidence of inflammation (C-reactive protein > or =10 mg/L), or iron overload (TSAT >80% for males and >70% for females) or serum iron values <5 micro mol/L, were removed. Among the referent individuals, iron and TSAT levels rose slightly until the teen years, at which time levels in males increased while those in females remained essentially constant. Between 20 and 70 years of age, males had 10-15% higher iron levels and 15-20% higher TSAT levels than females. When values were expressed as multiples of the age- and gender-specific median levels, the serum iron and TSAT observations fit log-Gaussian distributions reasonably well from the 20th to 99th centile, and the 10th to the 99th centile, respectively. After normalization, the Gaussian parameters can be used to assign a corresponding centile to an individual's measurement, simplifying interpretation. These data provide new and more detailed reference ranges for serum iron and TSAT.

Reference distributions for serum iron and transferrin saturation: A comparison of a large cohort to the world's literature

“…The results demonstrate that our approach to analyzing a large population (63) produces data comparable to those of previous smaller, more constrained studies, which obtained more detailed individual case data. The companion study reports reference data for serum iron and TSAT based on a large dataset with less reliance on individual health status.…”

“…If a published observation was based on less than 10 observations, it was combined with an adjacent age group from the same publication, whenever possible. For purposes of comparison, the solid and dashed lines represent the median levels for the two analytes found for males and females, respectively, in our companion study (63). Figure 1A shows the reported serum iron median values from the 33 publications considered acceptable for analysis of serum iron values.…”

“…The horizontal dotted lines display the weighted consensus value at the 2.5th and 97.5th centiles for previously published studies. The broken bars represent the observed and predicted reference ranges from our large cohort study (63). The skewed position of the dotted lines in both figures is the result of our population data having been log-transformed while all others were not.…”

“…The three symbol sizes represent the number of observations in each group (small, medium, and large circles represent 4100, 50-99, and 10-49, respectively). The solid (males) and dashed (females) lines are the regressed median levels from our large cohort study (63 Fig. 2.…”

SLC11A1(FormerlyNRAMP1) Gene Polymorphisms Associated with Pediatric Tuberculosis in China

“…The results revealed a significant association between the 3 UTR locus and TB in female children. Studies have proposed that, during their reproductive years, women lose body iron, resulting in a limited supply of iron ions in phagosomes for the generation of hydroxyl radicals and bactericidal activity [27]. Our study involved children aged !14 years who were not losing body iron.…”