Normal D-dimer levels in patients with latent tuberculosis infection

Studies have demonstrated a link between acute pulmonary tuberculosis and a hypercoagulable state, but there are no data on the coagulation state of patients with latent tuberculosis infection (LTI). The present prospective observational study was designed to help fill this gap. The sample included 84 patients (high school students and adults) with suspected LTI referred for the purified protein derivative (PPD) test. Results were read according to the criteria of the American Thoracic Society. Blood samples were collected at admission and assayed for D-dimer, the marker of the coagulation state, with the quantitative Miniquant test. D-dimer values were correlated with the PPD status and clinical parameters. Fifty-seven patients tested positive for LTI and 27 tested negative. There was no significant difference in D-dimer level between these groups (341 +/- 106 and 360 +/- 60 microg/ml, respectively). No significant correlation was found between D-dimer level and PPD status, patient age or occupation (health care worker or not), or clinical indication for the tuberculin test. The normal D-dimer levels in this series suggest that low-level inflammations such as LTI do not lead to a hypercoagulable state.