A comparison of reticulocyte results utilizing two different flow cytometers and the manual Miller disc

Reticulocytes were analysed using two different methods of analysis, flow cytometric and manual with the Miller disc. Comparison was made between results of two different flow cytometers and the manual method. Each method was also tested for precision. Samples were held for up to 48 hours at 4°C and retested by the flow cytometers to estimate stability of the specimens. All samples were whole blood specimens collected in EDTA anticoagulant from hospitalized patients. Sixty specimens were tested on the FACScan in replicate within four hours of collection. A random sample (n = 43) of these specimens was selected and tested in replicate within four hours by the manual method. Flow cytometer specimens were refrigerated and retested on the FACScan at intervals up to 30 hours. The procedure was repeated with another sample (n = 60) utilizing the Coulter Epics except that these specimens were retested at intervals up to 48 hours. Another sample (n = 60) was collected and tested on both the FACScan and Coulter Epics. Analysis by the t-test revealed no statistical differences between replicates indicating all methods were acceptably precise but the flow cytometers were more precise than the manual method. Comparison between methods showed low correlation between the manual method and the FACScan (r² = 0.661) and the manual method and the Coulter Epics (r² = 0.418) but higher correlation between the two flow cytometers (r² = 0.875). The flow cytometers gave consistently higher reticulocyte results than the manual methods. Analysis over time revealed that there was a significant statistical difference in results after 8 hours. The flow cytometers provide a precise analysis of reticulocytes which may translate into a more effective use of the reticulocyte count in monitoring erythropoietic activity following therapy or bone marrow transplant. Since the reticulocyte count is relatively stable, samples can be batched for analysis making this a time-saving method.