Flow cytometric analysis of reticulocytes using an RNA-binding fluorochrome

The reticulocyte count is an important parameter in the diagnosis of anaemia. The commonly used microscopic counting technique is, however, laborious and hampered by poor precision and low sensitivity. An alternative method has recently been developed, which is based on flow cytometric identification and quantification of reticulocytes after staining with an RNA-binding fluorochrome, thiazol orange. The two methods were compared both in a sample of healthy individuals and in patient specimens. The correlation between the methods was good, but the flow cytometric analysis consistently gave values approximately 1.5 times higher (reticulocytes in per cent of erythrocytes) than the microscopic technique. The coefficient of variation was significantly lower for the flow cytometric technique. Reference values for the reticulocyte count were determined and the effects of storage of specimens were evaluated. It is concluded that flow cytometric analysis of reticulocytes is more sensitive and has a better precision that the standard microscopic procedure.