Changes in platelet count and indices in pulmonary tuberculosis.

Background: Recent studies show that platelets have important roles in the immune system. Little is known about the clinical significance of platelet indices. Changes in platelet indices, including platelet distribution width (PDW), mean platelet volume (MPV) and plateletcrit, in pulmonary tuberculosis were investigated.

Methods: Platelet indices were quantified in 82 patients with active tuberculosis and 87 patients with inactive or non-tuberculous disease (controls). Radiological extent of the disease was assessed.

Results: There were significantly higher PDW (40.9+/-23.5% vs. 27.0+/-14.5%), MPV (10.05+/-2.36 vs. 8.83+/-1.47 fL) and plateletcrit (0.330+/-0166% vs. 0.266+/-0.128%) values in the active tuberculosis group, which decreased significantly with anti-tuberculous therapy. Erythrocyte sedimentation rate and plateletcrit showed significant correlation (r=0.54 and r=0.66) with radiological extent of tuberculosis, while PDW and MPV correlations with radiological extent of tuberculosis were also significant but weaker (r=0.31 and r=0.23). In a subpopulation of controls with pneumonia, which leads to acute phase reaction, PDW, MPV and plateletcrit values were significantly lower than in the tuberculosis group.

Conclusions: We suggest that PDW, MPV and plateletcrit change in tuberculosis and that these changes may not reflect only acute phase reaction and disease activity. The potential role of platelet indices in tuberculosis immunopathogenesis remains to be investigated.