Methods in pathology. The use of a colloidal silver (AgNOR) method in assessing bone marrow iron stores and sideroblasts.

Previous observations indicated that a colloidal silver (AgNOR) method identifies iron-containing bone marrow cells. In this study we examined AgNOR-stained bone marrow smears from 30 selected patients and compared the results with the conventional Prussian blue (PB) method for staining storage iron and sideroblasts, including ringed sideroblasts (RS). Erythroid cells were easily identified, and iron granules stained as distinct, small, round, black dots. In all cases containing sideroblasts and RS, their proportion expressed as the percentage of all normoblasts was higher with AgNOR than with PB. Pronormoblastic and basophilic sideroblasts were detected more often with AgNOR than with PB. Sideroblasts were noted in cases with no PB-stainable iron. Ringed sideroblasts were identified in a number of cases in which they were nondetectable with PB. In cases of myelodysplastic syndrome, pronormoblastic and basophilic RS were found more often than with PB. Hemosiderin deposits within the macrophages were clearly visualized as black aggregates and were seen in cases with no PB-stainable iron. There were no instances where iron or any category of sideroblasts was seen with PB only. In our sampling, the AgNOR method was more sensitive yet specific, and it produced staining results of superior quality.