From the Guidelines
To calculate iron deficiency, measure serum ferritin levels, and consider the presence of inflammation, as the diagnostic criteria may vary, with a serum ferritin level < 30 mcg/L or transferrin saturation < 16% defining iron deficiency in the absence of inflammation, and a lower limit of serum ferritin consistent with normal iron stores of 100 mcg/L in the presence of inflammation, as suggested by 1. When assessing iron deficiency, it is essential to consider the level of colonic inflammation, as it can affect the diagnostic criteria. In patients without evidence of inflammation, a serum ferritin level < 30 mcg/L or transferrin saturation < 16% indicates iron deficiency, while in the presence of inflammation, the lower limit of serum ferritin consistent with normal iron stores is 100 mcg/L, as noted in 1. Some key points to consider when calculating iron deficiency include:
- Serum ferritin level < 30 mcg/L or transferrin saturation < 16% defines iron deficiency in the absence of inflammation
- Lower limit of serum ferritin consistent with normal iron stores is 100 mcg/L in the presence of inflammation
- Transferrin saturation levels > 800 g/L are considered toxic and should be avoided, as mentioned in 1
- The determination of soluble transferrin receptor (sTfR) can help make a correct diagnosis, as it is high in iron deficiency and normal or low in anaemia of chronic disease (ACD), as suggested by 1 For a more comprehensive assessment, also check hemoglobin, mean corpuscular volume (MCV), and total iron-binding capacity (TIBC), and consider using Ganzoni’s formula or a simple scheme, such as the one used in the FERGIcor trial, to estimate the total body iron deficit, as discussed in 1. If iron deficiency is confirmed, treatment options may include oral iron supplementation, such as ferrous sulfate, or intravenous iron compounds, with the goal of normalizing hemoglobin levels and iron stores, as stated in 1.
From the FDA Drug Label
Transferrin saturation <20% and/or serum ferritin <100 ng/mL The calculation for iron deficiency is based on transferrin saturation and serum ferritin levels. Iron deficiency is defined as a transferrin saturation of less than 20% and/or a serum ferritin level of less than 100 ng/mL 2.
- Key factors:
- Transferrin saturation: <20%
- Serum ferritin: <100 ng/mL
From the Research
Calculation for Iron Deficiency
The calculation for iron deficiency is based on the total amount of iron necessary to correct iron deficiency, which can be determined using the patient's serum ferritin levels and the degree of anemia 3.
- The iron deficit can be calculated using a modified Ganzoni formula, which takes into account the patient's weight, hemoglobin level, and other factors 4.
- The total amount of iron necessary to correct iron deficiency can be calculated based on the iron deficit, with a typical dose of 5000 mg of oral elemental iron ingested over at least 1 month 5.
- For intravenous iron therapy, the dose can range from 1000 mg to 1500 mg, depending on the patient's iron deficit and other factors, with a higher dose potentially being more effective in correcting iron deficiency 4.
- The calculation of iron deficiency can also take into account the patient's individual characteristics, such as their age, sex, and medical history, as well as the presence of any underlying conditions that may be contributing to the iron deficiency 6.
Factors Affecting Iron Deficiency Calculation
Several factors can affect the calculation of iron deficiency, including:
- The patient's weight and body mass index (BMI) 4
- The patient's hemoglobin level and degree of anemia 5, 3
- The presence of any underlying medical conditions, such as chronic kidney disease or inflammatory bowel disease 6
- The patient's dietary intake of iron and other essential nutrients 3
- The patient's individual response to iron therapy, which can vary depending on factors such as their age, sex, and medical history 5, 4