TABLE 2.
Important confounders of iron status indicators1
| Confounder | Indicator and direction of change | Comment |
| Inflammation | SF ↑ | Ferritin is a positive acute-phase protein |
| Transferrin ↓ | Transferrin is a negative acute-phase protein | |
| Iron ↓ | The release of cytokines leads to increased uptake and retention of iron in reticuloendothelial system cells, e.g., iron becomes sequestered and is not available for transport to the bone marrow for erythropoiesis | |
| EP ↑ | ||
| Hemoglobin ↓ | ||
| Increased erythropoietic activity | EP, sTfR ↑ | In thalassemia, sickle cell anemia, and hemoglobinopathies |
| Lead poisoning | EP ↑ | Lead blocks the formation of heme and zinc protoporphyrin forms instead |
| Pregnancy | Hemoglobin ↓ | Plasma volume expansion results in hemodilution |
| Dehydration | Hemoglobin ↑ | The volume of fluid in blood drops and hemoglobin artificially rises |
| Smoking | Hemoglobin ↑ | Compensation for decreased oxygen intake in heavy smokers |
| Altitude | Hemoglobin ↑ | Compensation for decreased oxygen intake due at high altitude |
1
EP, erythrocyte protoporphyrin; SF, serum ferritin; sTfR, soluble transferrin receptor; ↑, increase in concentration; ↓, decrease in concentration.