Distribution and reference interval establishment of neutral-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), and platelet-to-lymphocyte ratio (PLR) in Chinese healthy adults

Background Neutral-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), and platelet-to-lymphocyte ratio (PLR) are associated with coronavirus disease 2019 (COVID-19) and many diseases, but there are few data about the reference interval (RI) of NLR, LMR, and PLR. Methods The neutrophil count, lymphocyte count, monocyte count, and platelet count of 404,272 Chinese healthy adults (>18 years old) were measured by Sysmex XE-2100 automatic hematology analyzer, and NLR, LMR, and PLR were calculated. According to CLSI C28-A3, the nonparametric 95% percentile interval is defined as the reference interval. Results The results of Mann-Whitney U test showed that NLR (p < .001) in male was significantly higher than that in female; LMR (p < .001) and PLR (p < .001) in male were significantly lower than that in female. Kruskal-Wallis H test showed that there were significant differences in NLR, LMR, and PLR among different genders and age groups (p < .001). The linear graph showed that the reference upper limit of NLR and PLR increased with age and the reference upper limit of LMR decreases with age in male population. In female population, the reference upper limit of NLR in 50-59 group, LMR in >80 group, and PLR in 70-79 group appeared a trough; the reference upper limit of NLR in >80 group, LMR in 50-59 group, and PLR in 40-49 group appeared peak. Conclusion The establishment of RI for NLR, LMR, and PLR in Chinese healthy adults according to gender and age will promote the standardization of clinical application.