Serum iron and total iron-binding capacity compared with serum ferritin in assessment of iron deficiency

Ferritin values for 250 selected sera were compared with values for iron, total iron-binding capacity (TIBC), and transferrin saturation, to assess the potential of the ferritin assay for the detection of latent iron deficiency. The specimens were grouped (50 in each group) according to their values for iron and TIBC. In Group 1 (low iron, high TIBC) the saturation and ferritin values both indicated iron deficiency in all but one. In the 100 specimens of Groups 2 (normal iron, high TIBC) and 4 (normal iron, high normal TIBC), the saturation values revealed 16 iron-deficient cases, the ferritin test 55. For Groups 3 (low iron, normal TIBC) and 5 (low iron, low TIBC), the ferritin test revealed fewer cases of iron deficiency than did the saturation values (37 cases vs 51 cases, in the 100 specimens). Evidently the ferritin test detects iron deficiency in many cases for whom the serum iron and TIBC tests are not positively indicative. The correlation of serum ferritin with iron, TIBC, and transferrin saturation in the five groups was good only in the case of specimens for which the TIBC was normal; if it was abnormal the correlation was very poor.