Monocytes predict prognosis and successful treatment in older patients with miliary tuberculosis

Background The increasing number of patients with miliary tuberculosis (MTB) is a concern in an aging society because of its high mortality rate. Several prognostic biomarkers for MTB have been identified; however, the predictive ability of monocytes as biomarkers remains unknown. This study demonstrates the usefulness of monocytes as prognostic biomarkers for MTB. Materials and methods We retrospectively compared the clinical findings of 52 patients with MTB hospitalized between April 2013 and October 2021. The predictive ability of biomarkers for 3-month prognosis and their cutoff values were calculated. Survival times and longitudinal changes in monocytes after initiating treatment were compared. Results A smaller number of monocytes (#M), higher lymphocyte-monocyte ratio (LMR), higher neutrophil-monocyte ratio, and poorer performance status were associated with death within 3 months. #M was an independent prognostic factor. #M and LMR exhibited the highest predictive performance compared to others using receiver operating characteristic curve analysis (area under the curve = 0.86 and 0.85, respectively). Survival time was shorter in patients with #M ≤ 200 cells/μL and LMR > 2.5. Rapidly increasing #M after treatment was related to better prognosis in patients with #M ≤ 200 cells/μL at diagnosis. Conclusions #M at diagnosis and longitudinal changes in monocytes are related to MTB prognosis.