Reference intervals for peripheral blood neutrophil CD64 index and monocyte HLA-DR in healthy adults

Neutrophil CD64 (nCD64) index and Monocyte HLA-DR (mHLADR) played an important role in the diagnosis of infection, however, reference intervals for these parameters in healthy adults remain insufficiently defined. This study aimed to established reference intervals for nCD64 index and mHLADR% in the peripheral blood from 285 healthy adults. All the subjects were grouped into subgroups according to sex (male and female) and age (20–51 years, 51–90 years). The analyses indicated age to be an important factor associated with changes in nCD64 index, which gradually increased from 20 to 90 years and showed a positive correlation with age (P < 0.0001). In contrast, no significant differences in mHLA-DR% were observed across gender or age groups (p > 0.05). Furthermore, no correlation was found between nCD64 index or mHLA-DR% and all the inflammatory derived indicators of blood routine (P > 0.05). In conclusion, the reference intervals established for the nCD64 index and mHLA-DR% in healthy adults may provide supportive information for monitoring immune status in the context of infectious diseases.