How should stainable iron in bone marrow films be assessed?

AIMS: To identify how many particles should be examined to enable a confident assessment of the presence or absence of iron stores and the quantity of iron in a bone marrow aspirate to be made. METHODS: One hundred and ninety consecutive bone marrow aspirate samples were stained with Perls' stain and the iron content of 10 consecutive particles was recorded. The first particle found to be positive and the particle that was most positive were also noted. RESULTS: A minimum of seven particles must be examined to establish the absence of stainable iron. A minimum of nine particles must be reviewed to see the maximum iron stores in 100% of samples and therefore make a valid judgment of whether iron stores are reduced, normal, or increased. By these criteria, 46% of the samples tested here could not be optimally assessed for absence of iron or maximum iron stores. CONCLUSIONS: The sensitivity of examination of bone marrow aspirates for iron stores can be optimised by increasing the number of particles reviewed to seven or more. This may require the staining of additional slides.