[Serum ferritin assay. Value and limitations].

There is a good correlation between serum ferritin and the amount of iron stored in the body. Reduced levels of serum ferritin are always found in iron deficiency but elevation of serum ferritin can occur without any iron overload. According to pathological situations, red cell ferritin, glycosylated ferritin or acidic ferritin measurements are useful tests for the differential diagnosis of increased serum ferritin concentration.