Automated fragmented red cell (FRC) counting in hemolytic anemia: Do poikilocytes and microcytes interfere?

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.