Microgram Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Microgram and links to relevant pages within the course.
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| Serum Iron Serum iron (SI) is a measure of circulating iron bound to transferrin and is reflective of total body iron. SI is elevated in hereditary hemochromatosis (HH) and acute hepatitis. SI is decreased in iron deficiency anemia and chronic inflammation. SI concentrations exhibit diurnal variation, with the lowest values occurring around midnight. In addition, specimens collected from the same individual at the same time of the day may exhibit day to day variations as high as 40%. SI determinations are also affected by diet, menstrual cycle, pregnancy, ingestion of iron supplements, and oral contraceptive use. SI levels alone are considered insensitive indicators of HH. SI is typically measured on automated analyzers using spectrophotometric methods. Iron in the sample is released from transferrin with an acid reagent, reduced to the ferrous state, and reacted with a chromogen such as bathophenanthroline or ferrozine. The intensity of the color change is proportional to the iron concentration. Interference can arise from the use of a hemolyzed sample and contamination of reagents and water with iron. A typical reference interval for SI is 60 - 150 micrograms/dL. SI is usually ordered along with its companion test, the total iron binding capacity (TIBC), or with transferrin (Tf).(2) | View Page |
| Transferrin and Total Iron Binding Capacity The test for transferrin (Tf) measures the concentration of the primary carrier protein for iron. Measuring total iron binding capacity (TIBC) is an indirect method of assessing transferrin and provides comparable information. The TIBC (or transferrin) are typically performed along with the SI. Taken together, these determinations are useful in the differential diagnosis of many disorders affecting iron metabolism, including hereditary hemochromatosis (HH) and iron deficiency anemia. Tf and TIBC are typically low-normal or decreased in HH and are increased in iron deficiency. Serum transferrin can be measured directly using immunochemical methods such as nephelometry and turbidimetry. TIBC is performed in a 2-step method by adding ferric iron to the specimen in sufficient quantity to completely fill all of the iron binding sites on transferrin. Excess, unbound iron is removed by adsorption with magnesium carbonate, alumina, or ion resin. The iron content of the saturated binding protein is then measured as described for SI. Serum is the specimen of choice for Tf and TIBC. TIBC is less subject than SI to day-to-day variation and other causes of variability.A typical reference interval for TIBC is 300 - 360 micrograms/dL.(2) | View Page |
| What is the transferrin saturation (TS) for a person with a serum iron of 200 micrograms/dL and a TIBC of 250 micrograms/dL? | View Page |
| UIBC Unsaturated iron binding capacity (UIBC) may also be used as a marker for altered iron metabolism. UIBC represents the portion of iron binding sites on transferrin that are not occupied by iron. Therefore, a low UIBC indicates that transferrin is highly saturated with iron, a finding consistent with hereditary hemochromatosis (HH). HH may be suspected when the UIBC is less than 143 micrograms/dL, a criterion suggested by the results of one study.(5)UIBC may be a lower cost alternative to the more complex transferrin saturation (TS). UIBC and SI are both fully automated procedures that are available on widely used laboratory instruments. The TIBC can be calculated by adding UIBC and SI, resulting in a value for TIBC that can be used for determining TS: TS = SI/(SI + UIBC) X 100 | View Page |