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Iron Deficiency Anemia: Likelihood Ratios

Introduction: This is anemia caused by low total body iron stores (e.g. from a GI bleed). Gold standard of diagnosis is Prussian Blue staining of a bone marrow biopsy (rarely done). Generally iron deficiency results in a microcytic, hypochromic anemia. The transferrin levels (aka TIBC) are increased, ferritin levels (which measure bone marrow stores) are decreased, and iron saturation is decreased.

In contrast, Anemia of Chronic Disease (inflammation) causes an anemia from poor mobilization of iron stores. These patients have increased iron stores and thus high ferritin (ferritin is also high because it is an acute phase reactant) and usually low transferrin levels.

Ferritin has been shown to be the most accurate test to distinguish these, even in a mixed clinical picture (see the J Gen Intern Med paper).

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Tags: Hematologic Tag this Diagnosis.

Differential Diagnoses include: Anemia of Chronic Disease, Thalassemia

Prevalence

Population / CalculatorPrevalence Comments / Study / Link
3%
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The likelihood ratios of findings for Iron Deficiency Anemia are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %. Post-Test Probability (Predictive Value): %. Switch to display mode.
**Note that calculating probabilities from more than one finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)
Good Positive and Negative Likelihood Ratios
FindingResult +LR-LR
[ + ] Decreased Ferritin + 0 - 3.20.1
[ + ] Decreased Ferritin + 0 - 160.2
[ + ] Decreased Ferritin + 0 - 10.60.2
[ + ] RDW, increased + 0 - 7.50.2
[ + ] Decreased Ferritin + 0 - 24.30.3
[ + ] Paleness + 0 - 3.30.3
Good Positive Likelihood Ratio
FindingResult +LR-LR
[ + ] Low Transferrin Saturation + 0 - 120.8
[ + ] Red Cell Protoporphyrin + 0 - 7.80.7
[ + ] Decreased MCV + 0 - 60.6
[ + ] Low Transferrin Saturation + 0 - 40.6
[ + ] RDW, increased + 0 - 2.60.9
Findings With Unspecified Accuracy
FindingResult +LR-LR
[ + ] Trasferrin Receptor (soluble) No accuracy specified.
[ + ] Increased Platelet Count No accuracy specified.