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Automated fragmented red cell (FRC) counting in hemolytic anemia: Do poikilocytes and microcytes interfere?
B R Rajalakshmi1, Shelby P Kunjukunju, S Suchitha
1Department of Pathology, JSS Medical College, JSS Academy of Higher Education and Research, Mysuru, Karnataka, India.
Introduction:
Automated hematology analyzers determine the fragmented red cells on the reticulocyte scattergram. The study was taken up to evaluate the accuracy of automated fragmented red cell (FRC%) counting in hemolytic anemia and to analyze the effect of interference of microcytosis and poikilocytosis on automated FRC counting.
Materials And Methods:
The study recruited cases of extravascular hemolysis, intravascular hemolysis, and microcytic hypochromic anemia (MHA). The automated FRC%, indices of microcytosis (mean corpuscular volume [MCV], percentage of microcytic red cells [Micro R%]), and anisopoikilocytosis (Red Cell Distribution Width-Coefficient of variation [RDW-CV]) were determined by the Mindray BC-6200 analyzer. The manual FRC count was compared with the automated FRC% in each group.
Results:
Bland-Altman plot suggested a high degree of agreement between manual and automated FRC% in intravascular hemolysis, with a cut-off of 0.94% for FRC% by receiver operating curve with 96.6% sensitivity and 100% specificity. Anisopoikilocytosis (measured by RDW-CV) showed positive linear correlation with FRC% in extravascular hemolysis ( r = 0.812, P < 0.001) and in MHA ( r = 0.552, P < 0.001), with no correlation in intravascular hemolysis ( r = 0.295, P = 0.121). Microcytosis (measured by Micro R%) showed no correlation with FRC% in extravascular and intravascular hemolysis ( P = 0.177 and P = 0.490, respectively), but showed a moderate positive correlation in MHA ( r = 0.461, P < 0.001). Whereas, FRC% showed a mild negative correlation with MCV in MHA ( r = -0.384, P < 0.001). The results suggest an interference of microcytosis and anisopoikilocytosis with automated FRC counting.
Conclusion:
The study recommends FRC% as a reliable parameter for indicating schistocytes in intravascular hemolysis, while there is an overestimation of FRC% in extravascular hemolysis due to anisopoikilocytosis. Caution must be exercised while interpreting FRC%, warranting a slide review to confirm the presence of schistocytes in cases with microcytosis and anisopoikilocytosis.
