New formula based on the discrepancy between impedance and fluorescence platelet to distinguish iron-deficiency anemia from non-transfusion-dependent thalassemia.

Introduction: Iron-deficiency anemia (IDA) and non-transfusion-dependent thalassemia (NTDT) are the 2 most common types of microcytic hypochromic anemia, but they are difficult to distinguish by routine tests. It is reported that red blood cells (RBCs) in thalassemia tend to be more microcytic and polymorphic, which may interfere with impedance platelet count (PLT-I). To correct PLT-I, fluorescence platelet count (PLT-F) can be used.

Methods: To establish a new discriminant formula based on the discrepancy between PLT-I and PLT-F (dPLT), this study retrospectively reviewed 350 patients: 145 with IDA and 205 with NTDT. The RBC and platelet parameters were obtained on a Sysmex XN-9000 system. Univariable and multivariable regression analyses were performed to screen the indicators. Diagnostic efficacy was analyzed using receiver operating characteristic curves.

Results: We found that the interference with PLT-I by RBCs was greater in patients with NTDT. The dPLT of patients with NTDT was statistically significantly higher than that of patients with IDA. Based on erythrocyte indices and dPLT, the diagnosis model, called PRMH (a model incorporating platelet difference, RBC count, mean corpuscular hemoglobin concentration, and hematocrit), was established.

Discussion: When compared with 11 reported formulas, the PRMH model showed better diagnostic efficacy, with a sensitivity of 88% and a specificity of 87%. Hence, the PRMH model can be used to distinguish NTDT from IDA.