Identification of Factors Determining Patterns of Serum C-Reactive Protein Level Reduction in Response to Treatment Initiation in Patients with Drug-Susceptible Pulmonary Tuberculosis.

Serum C-reactive protein (CRP) levels vary depending on radiological and bacteriological findings at the time of tuberculosis (TB) diagnosis. However, the utility of this biomarker in monitoring response to anti-TB treatment and identifying patients at risk of treatment failure is not well established. This study evaluated the impact of patients' baseline characteristics and anti-TB drug plasma exposure on the early reduction in serum CRP levels and its relationship with treatment response. We enrolled 42 patients with drug-susceptible pulmonary TB, who received a standard six-month regimen. The plasma concentrations of four anti-TB drugs were analysed using LC-MS/MS. Clinically relevant data, including serum CRP levels before and 10-12 days after treatment initiation (CRP), were obtained from electronic medical records and patient questionnaires. In 10-12 days, the median serum CRP level decreased from 21.9 to 6.4 mg/L. Lower body mass index, positive sputum-smear microscopy results, and lung cavitations at diagnosis were related to higher biomarker levels at both time points; smoking had a more pronounced effect on serum CRP levels. Variability in anti-TB drug plasma exposure did not significantly affect the reduction in serum CRP levels. The serum CRP levels, or fold change from the baseline, did not predict the time to sputum culture conversion. Disease severity and patient characteristics may influence the pattern of early CRP reduction, while anti-TB drug plasma exposure had no significant effect at this stage. These early changes in serum CRP levels were not a predictor of response to anti-TB therapy.