BACKGROUND: Diagnostic tools to identify incipient or subclinical TB stages will be helpful for preventive intervention. A simple biomarker to predict TB may be the monocytes to lymphocytes ratio (ML ratio) in peripheral blood.METHODS: We assessed the relationship between multiple time-updated ML ratio measurements and incidence of TB in people living with HIV (PLWH) after antiretroviral therapy (ART) was initiated. The ML ratio was updated at least every 6 months. TB incidence with corresponding 95% confidence intervals stratified according to time-updated ML ratio was calculated using ML ratio in quartiles.RESULTS: A total of 1305 PLWH were included in the analyses: 46 had incident TB and 1259 remained TB-free. The TB incidence rate was 10.3 (95% CI 7.1-14.9) cases/1000 patient-years (PYR) among participants with ML ratio ≥0.25 compared with 1.1⁄1000 PYR (95% CI 0.4-2.9) among those with ML ratio textless0.15. At cut-point 0.23, the ML ratio provided a diagnostic area under the receiver operating characteristics curve (AROC) of 0.849 (95% CI 0.784-0.914) and a sensitivity of 85% and specificity of 71%.CONCLUSION: Increased ML ratio was predictive of incident TB among PLWH on or after ART. The ML ratio can be a simple tool to stratify the risk of TB in PLWH.