Establishing a Cut-off Value for Myeloperoxidase Levels of Peripheral Blood Neutrophils in Patients with Varying Hemoglobin and Mean Cell Hemoglobin Concentration

Abstract

Background: Myeloperoxidase (MPO), a heme-containing peroxidase mostly found in lysosomal azurophilic granules in neutrophils. MPO catalyzes the conversion of chloride and hydrogen peroxide to hypochlorite during inflammation to act on the phagolysosome in microbial death. Since a large number of inflammatory diseases may be associated with anemia leading to varying low levels of plasma hemoglobin (Hb) and, MPO is also an iron containing protein, it is vital to study the behaviour of intracellular MPO in peripheral blood neutrophils. Objective: To establish cut-off values for MPO in neutrophils using peripheral blood smear with respect to varying Hb and Mean Cell Hemoglobin Concentration (MCHC) Methods: Total of 180 patients on iron treatment with varying hemoglobin concentrations, attended Hematology Clinic at Colombo North Teaching Hospital, Ragama, Sri Lanka were selected and peripheral blood smears of them were stained with modified quantitative approach of myeloperoxidase stain according to Peiris et al. (2023). The MCHC and Hb were obtained from the Hematology analyzer (Mindray, BC-6800). Data were categorized according to the subgroups of Hb and MCHC; 8.0<Hb (n=32), 8.0=<Hb<10.0 (n=57), 10.0=<Hb<12.0 (n=54), Hb>=12.0 (n=37) and MCHC<32 (n=51), MCHC>=32 (n=129). The statistical analysis was performed using SPSS version 26.0. Receiver Operating Characteristic (ROC) curve analysis was performed to establish the cut-off value of MPO with MCHC. Results: Means of MPO and MCHC displayed as almost constant values; about 50 and 32 in a reciprocal manner in all Hb groups. A cut-off value of 47.7 pertaining to MCHC two groups; MCHC=<32 and MCHC>32 was obtained by ROC analysis with AUC-0.637, sensitivity-68.6% and specificity-60.5%. Conclusion: The results showed the MPO is independent of the Hb centration. ROC curve results clearly indicate that once the MCHC appears below 32, the MPO is above 47.7. These initial findings should be validated by performing future research with an increased sample size.