From the Guidelines
An iron study typically includes a complete blood count (CBC) and iron parameters such as ferritin, percent transferrin saturation (TSAT) calculated by dividing the serum iron by the total iron binding capacity (TIBC). When evaluating iron status, it is essential to consider the underlying etiology of the iron deficiency (ID) and the presence of any ongoing losses or conditions that may affect iron absorption 1. The following tests are commonly included in an iron study:
- CBC to assess hemoglobin concentrations and reticulocyte count
- Iron parameters:
- Ferritin to evaluate iron stores
- TSAT to assess the availability of iron for erythropoiesis
- Serum iron and TIBC to calculate TSAT
- Additional tests that may be included in some cases:
- Soluble transferrin receptor (sTfR) to evaluate iron status in patients with inflammatory conditions
- Reticulocyte hemoglobin content (CHr) or reticulocyte hemoglobin equivalent (RET-He) to assess the functional availability of iron to the erythropoietic tissue It is crucial to interpret the results of these tests collectively, considering the clinical context and the presence of any underlying conditions that may affect iron metabolism 1. In contrast to older studies, such as the one published in 2012 1, which recommended an iron panel including serum iron, total iron binding capacity, and serum ferritin, the most recent guidelines emphasize the importance of evaluating iron status in the context of the underlying etiology and the presence of any ongoing losses or conditions that may affect iron absorption 1.
From the FDA Drug Label
16 HOW SUPPLIED Ferrous Sulfate Tablets are available as follows: Each tablet contains 324mg of ferrous sulfate, equivalent to 65mg of elemental iron, providing 362% of the U.S. recommended daily intake (RDI) of iron for adults and children 4 and older.
CONTAINS: Each tablet contains 324 mg of ferrous sulfate, equivalent to 65 mg of elemental iron, providing 362% of the U.S. recommended daily intake (RDI) of iron for adults and children 4 and older.
An iron study typically includes an assessment of the patient's iron levels, which may involve measuring:
- Elemental iron content
- Ferrous sulfate dosage However, the provided drug labels do not explicitly state what is included in an iron study. The information provided is about the ferrous sulfate tablets, their composition, and the recommended daily intake of iron. Since the labels do not directly address the question, no conclusion can be drawn about what is included in an iron study 2 2.
From the Research
Iron Study Components
- Serum ferritin measurement is considered the investigation of choice in iron deficiency 3
- Serum iron and Total Iron Binding Capacity (TIBC) measurements are also used to diagnose iron deficiency 3, 4
- Transferrin saturation, which is determined by dividing serum iron by TIBC and multiplying by 100, is another indicator of iron status 4
- Soluble transferrin receptor (sTfR) concentration is an indicator of functional iron deficiency that is not affected by inflammation 5
- Erythrocyte protoporphyrin is also used as an indicator of iron status 5
Limitations and Challenges
- Serum ferritin concentration can be affected by concomitant inflammation, making it challenging to interpret iron status 5
- Standardization of immunoassays for serum-based indicators is complicated by the heterogeneity of antibodies used and the absence of physicochemical reference methods 5
- Interpretation of sTfR concentration is challenging due to the lack of assay standardization, common reference ranges, and common cutoffs 5
Diagnostic Accuracy
- Transferrin or TIBC measurement outperforms iron measurement and saturation index in predicting iron deficiency 3
- Serum iron and TIBC give no additional information in the diagnosis of iron deficiency anemia and are redundant if serum ferritin is available 4
- The total body iron stores (TBI) model, which uses the log ratio of sTfR to SF, can better predict the absence of bone marrow iron than SF concentration alone 5