Calculation of Conversion Factors for the Number of Cells in Peripheral Blood Smear Microscopy to Determine Blood Cell Counts .

Abstract

Background: Automated full blood cell count (FBC) is a common test. The precision of FBC is monitored by internal quality control (IQC). Manual visual counting of cells in blood smears using light microscopes (LM) is an IQC method. Conversion factors calculated by visual counting cells in blood smears are vary between cell types and LM due to the differences in field of view (FOV). Due to differences in FOV, one conversion factor cannot be used between different LM brands and types. Objective: To determine conversion factors for automated cell counts estimated from cell counts in blood smears using different LM Methods: EDTA blood samples (n=30) and their FBC results by Mindray BC 5150 analyzer were obtained. Manual cell counting was performed using Leishman-stained blood smears on Olympus CX 23, CX 31, CX 43, Euromax, LaboMed, and Carl Zeiss microscopes. Red cells and platelets in ten oil immersion fields and white cells in ten high-power fields were counted to obtain mean manual cell counts for each sample. Duplicate counting was done to eliminate any personal errors. The conversion factors were calculated by dividing automated cell count by the corresponding manual mean count. Results: The conversion factor for platelet count was 13 000 for all except the Carl Zeiss microscope (12 000). The conversion factor for red blood cells was 1.4 for all except the LaboMed microscope (1.3). The conversion factor for total white blood cell count was 4000 for all the six microscopes. Conclusions: This study generated conversion factors for different microscopes and cell types for Mindray BC 5150 analyzer. Further studies are needed to evaluate the application of these conversion factors.