The diagnosis of Iron Deficiency Anemia (IDA) requires that a patient be anemic and show laboratory evidence of iron deficiency. Red blood cells in IDA are usually described as being microcytic (i.e., mean corpuscular volume less than 80 um3 [80 fL]) and hypochromic, however the manifestation of iron deficiency occurs in several stages.
Patients with a serum ferritin concentration less than 25 ng per mL (25 mcg per L) have a very high probability of being iron deficient. The most accurate initial diagnostic test for IDA is the serum ferritin measurement. Serum ferritin values greater than 100 ng per mL (100 mcg per L) indicate adequate iron stores and a low likelihood of IDA. In some populations, such as those with inflammatory disease or cirrhosis, these tests must be interpreted slightly differently because ferritin is an acute-phase reactant. Cutoffs for abnormality in these patients generally are higher.
Diagnosis of Iron Deficiency
| Adults with anemia* | Adults older than 65 | ||
| Test | Likeli- hood ratio |
Test | Likeli- hood ratio |
| Mean corpuscular volume | Mean corpuscular volume | ||
| Less than 70 um3 (70 fL) 70 to 74 um3 (74 fL) 75 to 79 um3 (75 to 79 fL) 80 to 84 um3 (80 to 84 fL) 85 to 89 um3 (85 to 89 fL) 90 ?m3 (90 fL) or more |
12.5 3.3 1.0 0.91 0.76 0.29 |
Less than 75 um3 75 to 85 um3 86 to 91 um3 (86 to 91 fL) 92 to 95 um3 (92 to 95 fL) More than 95 fL |
8.82 1.35 0.64 0.34 0.11 |
| Ferritin | Ferritin | ||
| Less than 15 ng/mL (15 mcg/L) 15 to 24 ng/mL (15 to 24 mcg/L) 25 to 34 ng/mL (25 to 34 mcg/L) 35 to 44 ng/mL (35 to 44 mcg/L) 45 to 100 ng/mL (45 to 100 mcg/L) More than 100 ng/mL |
51.8 8.8 2.5 1.8 0.54 0.08 |
Less than 19 ng/mL (19 mcg/L) 19 to 45 ng/mL (19 to 45 mcg/L) 46 to 100 ng/mL (46 to 100 mcg/L) More than 100 ng/mL |
41.0 3.1 0.46 0.13 |
| Transferrin saturation | Transferrin saturation | ||
| Less than 5 percent 5 to 9 percent 10 to 19 percent 20 to 29 percent 30 to 49 percent 50 percent or more |
10.5 2.5 0.81 0.52 0.43 0.15 |
Less than 5 percent 5 to 8 percent 8 to 21 percent More than 21 percent |
16.51 1.43 0.57 0.28 |
*Hemoglobin less than 13 g per dL [130 g per L] for men and less than 12 g per dL [120 g per L] for women
References:
- Killip S, Bennett JM, Chambers MD. Iron deficiency anemia. Am Fam Physician. 2007 Mar 1;75(5):671-8. [Medline]
- Guyatt GH, Oxman AD, Ali M, Willan A, McIlroy W, Patterson C. Laboratory diagnosis of iron-deficiency anemia: an overview. J Gen Intern Med. 1992 Mar-Apr;7(2):145-53. [Medline]
Created Sep 28, 2011.
