Iron The most common deficiency of a single nutrient in both the developing and the developed world Dietary iron requirements are determined by blood loss( including menstrual blood loss) and the needs of growth in children, adolescents, and pregnant women. Reduced body iron stores may be caused by inadequate dietary iron, excessive blood loss, or both. Introduction
The absorption of heme iron being much less efficiently regulated. Absorption of non-heme iron is influenced by other dietary factors. Biochemical data are a poor indication of dietary intake for individuals without substantial additional information about other dietary components, growth requirements, and blood loss. Iron
Serum Ferritin Ferritin is the principal iron storage protein. Serum ferritin level provides the best single indicator of iron stores. Average within-subject CV% =14.5% within-assay CV% = 4.3% Ferritin is decreased in proportion to the frequency of phlebotomy. Ferritin is increased in proportion to supplementation and iron overload.
Significant correlation between total daily iron intake and serum ferritin was not significantly observed. Meat intake was a significant predictor of serum ferritin level( a measure of heme iron). Serum Ferritin
Serum Iron Serum iron level is highly variable, and changes of more than 20% have been observed within 10 minutes among healthy subjects. an unreliable long-term measure
Transferrin Saturation and Total Iron-Binding Capacity Transferrin saturaiton = Serum iron TIBC TIBC is relatively stable, transferrin saturation is determined principally by changes in the serum iron concentration and is equally subject to short-term variation.
Erythrocyte Protoporphyrin Iron deficiency impaired heme synthesis and accumulation of protoporphyrin, a heme precursor, in erythrocytes. Measurement of EP level is a sensitive indicator of iron deficiency, but provides no information about iron overload.
EP is good for large-scale surveys: 1. small sample size(20ul blood) 2. the relative simplicity 3. reproducibility of the measurement Erythrocyte Protoporphyrin EP value <35 mg/dl, 88% sensitivity and 90% specificity as compared with serum ferritin. Correlation of EP with serum ferritin =0.66
Mean Corpuscular Volume Microcytosis of RBC can caused by thalassemia and inflammation. It is only a morphologic indicator of iron deficiency. Hemoglobin or Hematocrit More severe and long-standing iron deficiency reduced Hb level. Over hydration, hemoglobinopathies, Vit B12 deficiency and chronic diseases also caused lower Hb level.
Hair and Nails The method may be a measure for patient with hemochromatosis, but gives little information about levels over the normal range of iron intake. The biological significance of iron in hair and nails remains to be determined.
Other Determinants The major determinant of iron blood loss Blood donations and menstrual history should be considered in interpretation of iron status. Oral contraceptive users reduced menstrual blood loss
Summary The use of several biochemical indicators of iron status provides a more sensitive and specific assessment. The appropriate cut-off values should be carefully determined to categorize subjects according to diagnostic groups.
Vitamin B1 5% U.S. adults over 60 years old impaired thiamin status The prevalence among the poor, the chronically ill, the institutionalized.
The best method for assessing thiamine nutriture in the population is the stimulation of erythrocyte transketolase by thiamine pyrophosphate(TPP) Transketolase activity after addition of TPP Transketolase activity before addition of TPP Greater than 1 imply deficiency of endogenous thiamine Vitamin B1
Development of automated procedures make this method more applicable to large studies. Little sample(50ul whole blood) is required for the calorimetric method. Correlation between calorimetric method and FFQ for thiamin intake is 0.02. Vitamin B1
HPLC is a precise technique for measuring vitamin B1 in plasma and whole blood, but not a useful measure of thiamine status. (Thiamin deficiency does not cause a large reduction in blood level.) Urinary thiamin level is not a good index of thiamine nutriture. Vitamin B1
Automatically measuring RBC transketolase stimulation provide reproducible and sensitive results.(2.7% within-run ； 4.1% between-run) Long-term stability of RBC transketolase is uncertain. Vitamin B1
Measurement of Other Determinants ： DM and polyneuritis low RBC transketolase activity Pernicious anemia high activity Heavy alcohol intake inhibit ： thiamine absorption and metabolism Vitamin B1