Improved method for assessing iron stores in the bone marrow

Abstract

Background: Bone marrow iron microscopy has been the "gold standard" method of assessing iron deficiency. However, the commonly used method of grading marrow iron remains highly subjective.

Aim: To improve the bone marrow grading method by developing a detailed protocol that assesses iron in fragments, in macrophages around fragments and in erythroblasts.

Methods: A descriptive study of marrow aspirates of 303 children (aged 6-60 months) with severe anaemia and 22 controls (children undergoing elective surgery) was conducted at hospitals in southern Malawi (2002-04).

Results: Using an intensive marrow iron grading method, 22% and 39% of cases and controls had deficient iron stores, and 40% and 46% had functional iron deficiency, respectively. Further evaluation of the iron status classification by the intensive method showed that functional iron deficiency was associated with significantly increased C-reactive protein concentrations (126.7 (85.6) mg/l), and iron stores deficiency with significantly increased soluble transferrin receptor concentrations (21.7 (12.5) mug/ml).

Conclusions: Iron assessment can be greatly improved by a more intense marrow examination. This provides a useful iron status classification which is of particular importance in areas where there is a high rate of inflammatory conditions.

Figure 1

Bone marrow fragment showing iron deposits at ×400 magnification (top), and ×1000 magnification showing erythroblasts, iron and malaria pigment within macrophages (bottom).

Figure 2

Flow chart showing the number of children recruited and the number of bone marrow samples finally assessed using both Gale’s and intensive histological grading methods.

Figure 3

Error bar graphs for mean log ferritin, soluble transferrin receptor (sTfR) and C-reactive protein (CRP) concentrations for the different iron status classes using the intensive grading method.